2.1 Treatment of Uncomplicated P. falciparum Malaria

For treatment of uncomplicated P. falciparum malaria in adults: Orally, 648 mg (two capsules) every 8 hours for 7 days [see Clinical Studies (14)].

Quinine sulfate capsules should be taken with food to minimize gastric upset [see Clinical Pharmacology (12.3)].

2.2 Renal Impairment

In patients with acute uncomplicated malaria and severe chronic renal impairment, the following dosage regimen is recommended: one loading dose of 648 mg quinine sulfate capsules followed 12 hours later by maintenance doses of 324 mg every 12 hours. The effects of mild and moderate renal impairment on the safety and pharmacokinetics of quinine sulfate are not known [see Use in Specific Populations (8.6) and Clinical Pharmacology (12.3)].

2.3 Hepatic Impairment

Adjustment of the recommended dose is not required in mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment, but patients should be monitored closely for adverse effects of quinine. Quinine should not be administered in patients with severe (Child-Pugh C) hepatic impairment [see Use in Specific Populations (8.7) and Clinical Pharmacology (12.3)].

5.1 Use of Quinine Sulfate Capsules for Treatment or Prevention of Nocturnal Leg Cramps

Quinine sulfate capsules may cause unpredictable serious and life-threatening hematologic reactions including thrombocytopenia and hemolytic-uremic syndrome/thrombotic thrombocytopenic purpura (HUS/TTP) in addition to hypersensitivity reactions, QT prolongation, serious cardiac arrhythmias including torsades de pointes, and other serious adverse events requiring medical intervention and hospitalization. Chronic renal impairment associated with the development of TTP, and fatalities have also been reported. The risk associated with the use of quinine sulfate capsules in the absence of evidence of its effectiveness for treatment or prevention of nocturnal leg cramps, outweighs any potential benefit in treating and/or preventing this benign, self-limiting condition [see Boxed Warning and Contraindications (4)].

5.2 Thrombocytopenia

Quinine-induced thrombocytopenia is an immune-mediated disorder. Severe cases of thrombocytopenia that are fatal or life threatening have been reported, including cases of HUS/TTP. Chronic renal impairment associated with the development of TTP has also been reported. Thrombocytopenia usually resolves within a week upon discontinuation of quinine. If quinine is not stopped, a patient is at risk for fatal hemorrhage. Upon re-exposure to quinine from any source, a patient with quinine-dependent antibodies could develop thrombocytopenia that is more rapid in onset and more severe than the original episode.

5.3 Hemolytic Anemia

Acute hemolytic anemia has been reported in patients receiving quinine for treatment of malaria, including patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. The cause for the acute hemolytic anemia in quinine-treated patients with malaria and its potential relationship with G6PD deficiency has not been determined. Closely monitor hemoglobin and hematocrit during quinine treatment. Quinine should be discontinued if patients develop acute hemolytic anemia.

5.4 QT Prolongation and Ventricular Arrhythmias

QT interval prolongation has been a consistent finding in studies which evaluated electrocardiographic changes with oral or parenteral quinine administration, regardless of age, clinical status, or severity of disease. The maximum increase in QT interval has been shown to correspond with peak quinine plasma concentration [see Clinical Pharmacology (12.2)]. Quinine sulfate has been rarely associated with potentially fatal cardiac arrhythmias, including torsades de pointes, and ventricular fibrillation.

Quinine sulfate capsules have been shown to cause concentration-dependent prolongation of the PR and QRS interval. At particular risk are patients with underlying structural heart disease and preexisting conduction system abnormalities, elderly patients with sick sinus syndrome, patients with atrial fibrillation with slow ventricular response, patients with myocardial ischemia or patients receiving drugs known to prolong the PR interval (e.g. verapamil) or QRS interval (e.g. flecainide or quinidine) [see Clinical Pharmacology (12.2)].

Quinine sulfate capsules are not recommended for use with other drugs known to cause QT prolongation, including Class IA antiarrhythmic agents (e.g., quinidine, procainamide, disopyramide), and Class III antiarrhythmic agents (e.g., amiodarone, sotalol, dofetilide).

The use of macrolide antibiotics such as erythromycin should be avoided in patients receiving quinine sulfate capsules. Fatal torsades de pointes was reported in an elderly patient who received concomitant quinine, erythromycin, and dopamine. Although a causal relationship between a specific drug and the arrhythmia was not established in this case, erythromycin is a CYP3A4 inhibitor and has been shown to increase quinine plasma levels when used concomitantly. A related macrolide antibiotic, troleandomycin, has also been shown to increase quinine exposure in a pharmacokinetic study [see Drug Interactions (7)].

Quinine may inhibit the metabolism of certain drugs that are CYP3A4 substrates and are known to cause QT prolongation, e.g., astemizole, cisapride, terfenadine, pimozide, halofantrine and quinidine. Torsades de pointes has been reported in patients who received concomitant quinine and astemizole. Therefore, concurrent use of quinine sulfate capsules with these medications, or drugs with similar properties, should be avoided [see Drug Interactions (7)].

Concomitant administration of quinine sulfate capsules with the antimalarial drugs, mefloquine or halofantrine, may result in electrocardiographic abnormalities, including QT prolongation, and increase the risk for torsades de pointes or other serious ventricular arrhythmias. Concurrent use of quinine sulfate capsules and mefloquine may also increase the risk of seizures [see Drug Interactions (7)].

Quinine sulfate capsules should also be avoided in patients with known prolongation of QT interval and in patients with clinical conditions known to prolong the QT interval, such as uncorrected hypokalemia, bradycardia, and certain cardiac conditions [see Contraindications (4)].

5.5 Concomitant Use of Rifampin

Treatment failures may result from the concurrent use of rifampin with quinine sulfate capsules, due to decreased plasma concentrations of quinine, and concomitant use of these medications should be avoided [see Drug Interactions (7)].

5.6 Concomitant Use of Neuromuscular Blocking Agents

The use of neuromuscular blocking agents should be avoided in patients receiving quinine sulfate capsules. In one patient who received pancuronium during an operative procedure, subsequent administration of quinine resulted in respiratory depression and apnea. Although there are no clinical reports with succinylcholine or tubocurarine, quinine may also potentiate neuromuscular blockade when used with these drugs [see Drug Interactions (7)].

5.7 Hypersensitivity

Serious hypersensitivity reactions reported with quinine sulfate include anaphylactic shock, anaphylactoid reactions, urticaria, serious skin rashes, including Stevens-Johnson syndrome and toxic epidermal necrolysis, angioedema, facial edema, bronchospasm, and pruritus.

A number of other serious adverse reactions reported with quinine, including thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS), thrombocytopenia, immune thrombocytopenic purpura (ITP), blackwater fever, disseminated intravascular coagulation, leukopenia, neutropenia, granulomatous hepatitis, and acute interstitial nephritis may also be due to hypersensitivity reactions.

Quinine sulfate capsules should be discontinued in case of any signs or symptoms of hypersensitivity [see Contraindications (4)].

5.8 Atrial Fibrillation and Flutter

Quinine sulfate capsules should be used with caution in patients with atrial fibrillation or atrial flutter. A paradoxical increase in ventricular response rate may occur with quinine, similar to that observed with quinidine. If digoxin is used to prevent a rapid ventricular response, serum digoxin levels should be closely monitored, because digoxin levels may be increased with use of quinine [see Drug Interactions (7)].

5.9 Hypoglycemia

Quinine stimulates release of insulin from the pancreas, and patients, especially pregnant women, may experience clinically significant hypoglycemia.

6.1 Overall

Quinine can adversely affect almost every body system. The most common adverse events associated with quinine use are a cluster of symptoms called "cinchonism", which occurs to some degree in almost all patients taking quinine. Symptoms of mild cinchonism include headache, vasodilation and sweating, nausea, tinnitus, hearing impairment, vertigo or dizziness, blurred vision, and disturbance in color perception. More severe symptoms of cinchonism are vomiting, diarrhea, abdominal pain, deafness, blindness, and disturbances in cardiac rhythm or conduction. Most symptoms of cinchonism are reversible and resolve with discontinuation of quinine.

The following adverse reactions have been reported with quinine sulfate. Because these reactions have been reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

General: fever, chills, sweating, flushing, asthenia, lupus-like syndrome, and hypersensitivity reactions.

Hematologic: agranulocytosis, hypoprothrombinemia, thrombocytopenia, disseminated intravascular coagulation, hemolytic anemia; hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, idiopathic thrombocytopenic purpura, petechiae, ecchymosis, hemorrhage, coagulopathy, blackwater fever, leukopenia, neutropenia, pancytopenia, aplastic anemia, and lupus anticoagulant.

Neuropsychiatric: headache, diplopia, confusion, altered mental status, seizures, coma, disorientation, tremors, restlessness, ataxia, acute dystonic reaction, aphasia, and suicide.

Dermatologic: cutaneous rashes, including urticarial, papular, or scarlatinal rashes, pruritus, bullous dermatitis, exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, fixed drug eruption, photosensitivity reactions, allergic contact dermatitis, acral necrosis, and cutaneous vasculitis.

Respiratory: asthma, dyspnea, pulmonary edema.

Cardiovascular: chest pain, vasodilatation, hypotension, postural hypotension, tachycardia, bradycardia, palpitations, syncope, atrioventricular block, atrial fibrillation, irregular rhythm, unifocal premature ventricular contractions, nodal escape beats, U waves, QT prolongation, ventricular fibrillation, ventricular tachycardia, torsades de pointes, and cardiac arrest.

Gastrointestinal: nausea, vomiting, diarrhea, abdominal pain, gastric irritation, and esophagitis.

Hepatobiliary: granulomatous hepatitis, hepatitis, jaundice, and abnormal liver function tests.

Metabolic: hypoglycemia and anorexia.

Musculoskeletal: myalgias and muscle weakness.

Renal: hemoglobinuria, renal failure, renal impairment, and acute interstitial nephritis.

Special Senses: visual disturbances, including blurred vision with scotomata, sudden loss of vision, photophobia, diplopia, night blindness, diminished visual fields, fixed pupillary dilatation, disturbed color vision, optic neuritis, blindness, vertigo, tinnitus, hearing impairment, and deafness.

8.1 Pregnancy

Risk Summary
Prolonged experience with quinine in pregnant women over several decades, based on published prospective and retrospective observational studies, surveys, safety and efficacy studies, review articles, case reports and case series have not identified a drug associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes (see Data).

In animal reproduction studies, administration of quinine by multiple routes of administration to pregnant rabbits, dogs, guinea pigs, rats, and monkeys during the period of organogenesis at doses of 0.25 to 2 times the maximum recommended human dose (MRHD) based on body surface area (BSA), produced embryo-fetal toxicity including malformations. Offspring of pregnant rats administered oral quinine sulfate during mating, gestation, and lactation at a dose approximately equivalent to 0.1 times the MRHD based on BSA comparison experienced impaired growth and delayed physical development (see Data).

The estimated background risk of major birth defects and miscarriage for the indicated population are unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.

Clinical Considerations
Disease-associated maternal and/or embryo/fetal risk
Malaria during and after pregnancy increases the risk for adverse pregnancy and neonatal outcomes, including maternal anemia, severe malaria, spontaneous abortion, stillbirths, preterm delivery, low birth weight, intrauterine growth retardation, congenital malaria, and maternal and neonatal mortality.

Maternal adverse reactions
An increased incidence of hypoglycemia, due to increased pancreatic secretion of insulin, has been reported with quinine use, in pregnant women, especially during the third trimester 1. Monitor glucose levels in pregnant woman taking quinine. Tinnitus, vomiting, dizziness, and nausea are commonly reported adverse reactions in pregnant women taking quinine. Pregnant women are also at risk for a rare triad of complications: massive hemolysis, hemoglobinemia, and hemoglobinuria 2.

Labor or delivery
In doses several times higher than those used to treat malaria, quinine may cause uterine contractions; however, there is no evidence that quinine causes uterine contractions at the doses recommended for the treatment of malaria.

Data
Human Data
Quinine crosses the placenta with measurable blood concentrations in the fetus. In 8 women who delivered live infants 1 to 6 days after starting quinine therapy, umbilical cord plasma quinine concentrations were between 1.0 and 4.6 mg/L (mean 2.4 mg/L) and the mean (±SD) ratio of cord plasma to maternal plasma quinine concentrations was 0.32 ± 0.14. Quinine levels in the fetus may not be therapeutic.

Adverse outcomes have been identified in the post-marketing experience with quinine during pregnancy. Because these outcomes are reported from varied data sources and have inconsistent findings and/or important methodological limitations, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

In studies in which more than 893 pregnant women were treated with quinine for malaria in the first trimester, no quinine-associated increases in the incidence of congenital anomalies were observed compared with other antimalarial drugs 3.

A retrospective study of women with P. falciparum malaria who were treated with oral quinine sulfate 10 mg/kg 3 times daily for 7 days at any time in pregnancy reported no significant difference in the rate of stillbirths at >28 weeks of gestation in women treated with quinine (10 of 633 women [1.6%]) as compared with a control group without malaria or exposure to antimalarial drugs during pregnancy (40 of 2201 women [1.8%]). The overall rate of congenital malformations (9 of 633 offspring [1.4%]) was not different for women who were treated with quinine sulfate compared with the control group (38 of 2201 offspring [1.7%]). The spontaneous abortion rate was higher in the control group (10.9%) than in women treated with quinine sulfate (3.5%) [OR = 3.1; 95% CI 2.1 to 4.7]. An epidemiologic survey that included 104 mother-child pairs exposed to quinine during the first 4 months of pregnancy, found no increased risk of structural birth defects was seen (2 fetal malformations [1.9%]). Case reports describe deafness and optic nerve hypoplasia in children exposed in utero due to maternal ingestion of high doses of quinine.

Animal Data
In animal developmental studies conducted in multiple animal species 4, pregnant animals received quinine by the subcutaneous, intramuscular, and oral routes at doses 0.25 to 2 times the maximum recommended human dose (MRHD) based on body surface area (BSA). Increases in fetal death were observed in utero in pregnant rabbits at maternal doses ≥ 100 mg/kg/day and in pregnant dogs at ≥ 15 mg/kg/day corresponding to dose levels approximately 0.5 and 0.25 times the MRHD respectively based on BSA comparisons. Rabbit offspring had increased rates of degenerated auditory nerve and spiral ganglion and increased rates of CNS anomalies such as anencephaly and microcephaly at a dose of 130 mg/kg/day corresponding to a maternal dose approximately 1.3 times the MRHD based on BSA comparison. Guinea pig offspring had increased rates of cochlear hemorrhage at maternal doses of 200 mg/kg corresponding to a dose level of approximately 1.4 times the MRHD based on BSA comparison. No fetal malformations were observed in rats at maternal doses up to 300 mg/kg/day and in monkeys at maternal doses up to 200 mg/kg/day corresponding to doses approximately 1 and 2 times the MRHD respectively based on BSA comparisons.

In a pre-postnatal study, pregnant rats received quinine sulfate in feed beginning two weeks prior to mating, through gestation, and lactation. An estimated oral dose of quinine sulfate of 20 mg/kg/day corresponding to approximately 0.1 times the MRHD based on BSA comparison resulted in offspring with impaired growth, lower body weights at birth and during the lactation period, and delayed physical development of teeth eruption and eye opening during the lactation period.

8.2 Lactation

Risk Summary
Quinine is present in human milk. It is estimated that breastfed infants would receive less than 2 to 3 mg per day of quinine base (< 0.4% of the maternal dose) via breast milk (see Data). There are no data on the effects of quinine on the breastfed infant or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for quinine sulfate capsules and any potential adverse effects on the breastfed child from quinine sulfate capsules or from the underlying maternal condition.

Data
No toxicity was reported in infants in a single study where oral quinine sulfate (10 mg/kg every 8 hours for 1 to 10 days) was administered to 25 lactating women. Quinine concentrations in breast milk are approximately 31% of quinine concentrations in maternal plasma.

8.3 Females and Males of Reproductive Potential

Infertility
In a published study 5 in 5 men receiving oral tablets of 600 mg quinine three times a day for one week, sperm motility was decreased and percent sperm with abnormal morphology was increased, but sperm count and serum testosterone were unaffected.

Based on findings from animal studies, quinine sulfate capsules may impair fertility [see Nonclinical Toxicology (13.1)].

8.4 Pediatric Use

The safety and efficacy of quinine sulfate capsules in pediatric patients under the age of 16 has not been established.

8.5 Geriatric Use

Clinical studies of quinine sulfate did not include sufficient numbers of subjects aged 65 and over to determine whether they respond to treatment differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients.

8.6 Renal Impairment

Clearance of quinine is decreased in patients with severe chronic renal failure. The dosage and dosing frequency should be reduced [see Dosage and Administration (2.2) and Clinical Pharmacology (12.3)].

8.7 Hepatic Impairment

In patients with severe hepatic impairment (Child-Pugh C), quinine oral clearance (CL/F) is decreased, volume of distribution (V d/F) is increased, and half-life is prolonged, relative to subjects with normal liver function. Therefore, quinine is not indicated in patients with severe hepatic impairment and alternate therapy should be administered [see Dosage and Administration (2.3) and Clinical Pharmacology (12.3)].

Close monitoring is recommended for patients with mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment, as exposure to quinine may be increased relative to subjects with normal liver function [see Clinical Pharmacology (12.3)].

12.1 Mechanism of Action

Quinine is an antimalarial agent [see Clinical Pharmacology (12.4)].

12.2 Pharmacodynamics

QTc interval prolongation was studied in a double-blind, multiple dose, placebo- and positive-controlled crossover study in young (N=13, 20 to 39 years) and elderly (N=13, 65 to 78 years) subjects. After 7 days of dosing with quinine sulfate capsules 648 mg three times daily, the maximum mean (95% upper confidence bound) differences in QTcI from placebo after baseline correction was 27.7 (32.2) ms.

Prolongation of the PR and QRS interval was also noted in subjects receiving quinine sulfate capsules. The maximum mean (95% upper confidence bound) difference in PR from placebo after baseline-correction was 14.5 (18.0) ms. The maximum mean (95% upper confidence bound) difference in QRS from placebo after baseline-correction was 11.5 (13.3) ms [see Warnings and Precautions (5.4)].

12.3 Pharmacokinetics

Absorption
The oral bioavailability of quinine is 76 to 88% in healthy adults. Quinine exposure is higher in patients with malaria than in healthy subjects. After a single oral dose of quinine sulfate, the mean quinine T max was longer, and mean AUC and C max were higher in patients with uncomplicated P. falciparum malaria than in healthy subjects, as shown in Table 2 below.

Quinine sulfate capsules may be administered without regard to meals. When a single oral 324 mg capsule of quinine sulfate capsules was administered to healthy subjects (N=26) with a standardized high-fat breakfast, the mean T max of quinine was prolonged to about 4.0 hours, but the mean C max and AUC 0-24h were similar to those achieved when quinine sulfate capsules was given under fasted conditions [see Dosage and Administration (2.1)].

Distribution
In patients with malaria, the volume of distribution (V d/F) decreases in proportion to the severity of the infection. In published studies with healthy subjects who received a single oral 600 mg dose of quinine sulfate, the mean V d/F ranged from 2.5 to 7.1 L/kg.

Quinine is moderately protein-bound in blood in healthy subjects, ranging from 69 to 92%. During active malarial infection, protein binding of quinine is increased to 78 to 95%, corresponding to the increase in α 1-acid glycoprotein that occurs with malaria infection.

Intra-erythrocytic levels of quinine are approximately 30 to 50% of the plasma concentration.

Quinine penetrates relatively poorly into the cerebrospinal fluid (CSF) in patients with cerebral malaria, with CSF concentration approximately 2 to 7% of plasma concentration.

In one study, quinine concentrations in placental cord blood and breast milk were approximately 32% and 31%, respectively, of quinine concentrations in maternal plasma. The estimated total dose of quinine secreted into breast milk was less than 2 to 3 mg per day [see Use in Specific Populations (8.1, 8.2)].

Elimination
Metabolism
Quinine is metabolized almost exclusively via hepatic oxidative cytochrome P450 (CYP) pathways, resulting in four primary metabolites, 3-hydroxyquinine, 2´-quinone, O-desmethylquinine, and 10,11-dihydroxydihydroquinine. Six secondary metabolites result from further biotransformation of the primary metabolites. The major metabolite, 3-hydroxyquinine, is less active than the parent drug.

In vitro studies using human liver microsomes and recombinant P450 enzymes have shown that quinine is metabolized mainly by CYP3A4. Depending on the in vitro experimental conditions, other enzymes, including CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP2E1 were shown to have some role in the metabolism of quinine.

Excretion
Quinine is eliminated primarily via hepatic biotransformation. Approximately 20% of quinine is excreted unchanged in urine. Because quinine is reabsorbed when the urine is alkaline, renal excretion of the drug is twice as rapid when the urine is acidic than when it is alkaline.

In various published studies, healthy subjects who received a single oral 600 mg dose of quinine sulfate exhibited a mean plasma clearance ranging from 0.08 to 0.47 L/h/kg (median value: 0.17 L/h/kg) with a mean plasma elimination half-life of 9.7 to 12.5 hours.

In 15 patients with uncomplicated malaria who received a 10 mg/kg oral dose of quinine sulfate, the mean total clearance of quinine was slower (approximately 0.09 L/h/kg) during the acute phase of the infection, and faster (approximately 0.16 L/h/kg) during the recovery or convalescent phase.

Extracorporeal Elimination: Administration of multiple-dose activated charcoal (50 grams administered 4 hours after quinine dosing followed by 3 further doses over the next 12 hours) decreased the mean quinine elimination half-life from 8.2 to 4.6 hours, and increased the mean quinine clearance by 56% (from 11.8 L/h to 18.4 L/h) in 7 healthy adult subjects who received a single oral 600 mg dose of quinine sulfate. Likewise, in 5 symptomatic patients with acute quinine poisoning who received multiple-dose activated charcoal (50 grams every 4 hours), the mean quinine elimination half-life was shortened to 8.1 hours in comparison to a half-life of approximately 26 hours in patients who did not receive activated charcoal [see Overdosage (10)].

In 6 patients with quinine poisoning, forced acid diuresis did not change the half-life of quinine elimination (25.1 ± 4.6 hours vs. 26.5 ± 5.8 hours), or the amount of unchanged quinine recovered in the urine, in comparison to 8 patients not treated in this manner [see Overdosage (10)].

Specific Populations
Pediatric Patients
The pharmacokinetics of quinine in children (1.5 to 12 years old) with uncomplicated P. falciparum malaria appear to be similar to that seen in adults with uncomplicated malaria. Furthermore, as seen in adults, the mean total clearance and the volume of distribution of quinine were reduced in pediatric patients with malaria as compared to the healthy pediatric controls. Table 3 below provides a comparison of the mean ± SD pharmacokinetic parameters of quinine in pediatric patients versus healthy pediatric controls.

Geriatric Patients
Following a single oral dose of 600 mg quinine sulfate, the mean AUC was about 38% higher in 8 healthy elderly subjects (65 to 78 years old) than in 12 younger subjects (20 to 35 years old). The mean T max and C max were similar in elderly and younger subjects after a single oral dose of quinine sulfate 600 mg. The mean oral clearance of quinine was significantly decreased, and the mean elimination half-life was significantly increased in elderly subjects compared with younger subjects (0.06 versus 0.08 L/h/kg, and 18.4 hours versus 10.5 hours, respectively). Although there was no significant difference in the renal clearance of quinine between the two age groups, elderly subjects excreted a larger proportion of the dose in urine as unchanged drug than younger subjects (16.6% versus 11.2%).

After a single 648 mg dose or at steady state, following quinine sulfate 648 mg given three times daily for 7 days, no difference in the rate and extent of absorption or clearance of quinine was seen between 13 elderly subjects (65 to 78 years old) and 14 young subjects (20 to 39 years old). The mean elimination half-life was 20% longer in the elderly subjects (24.0 hours) than in younger subjects (20.0 hours). The steady state C max (±SD) and AUC 0-8 (±SD) for healthy volunteers are 6.8 ± 1.24 mcg/mL and 48.8 ± 9.15 mcg*h/mL, respectively, following 7 days of oral quinine sulfate 648 mg three times daily. The steady state pharmacokinetic parameters in healthy elderly subjects were similar to the pharmacokinetic parameters in healthy young subjects.

Patients with Renal Impairment
Following a single oral 600 mg dose of quinine sulfate in otherwise healthy subjects with severe chronic renal failure not receiving any form of dialysis (mean serum creatinine = 9.6 mg/dL), the median AUC was higher by 195% and the median C max was higher by 79% than in subjects with normal renal function (mean serum creatinine = 1 mg/dL). The mean plasma half-life in subjects with severe chronic renal impairment was prolonged to 26 hours compared to 9.7 hours in the healthy controls. Computer assisted modeling and simulation indicates that in patients with malaria and severe chronic renal failure, a dosage regimen consisting of one loading dose of 648 mg followed 12 hours later by a maintenance dosing regimen of 324 mg every 12 hours will provide adequate systemic exposure to quinine [see Dosage and Administration (2.2)]. The effects of mild and moderate renal impairment on the pharmacokinetics and safety of quinine sulfate are not known.

Negligible to minimal amounts of circulating quinine in the blood are removed by hemodialysis or hemofiltration. In subjects with chronic renal failure (CRF) on hemodialysis, only about 6.5% of quinine is removed in 1 hour. Plasma quinine concentrations do not change during or shortly after hemofiltration in subjects with CRF [see Overdosage (10)].

Patients with Hepatic Impairment
In otherwise healthy subjects with mild hepatic impairment (Child-Pugh A; N=10), who received a single 500 mg dose of quinine sulfate, there was no significant difference in quinine pharmacokinetic parameters or exposure to the primary metabolite, 3-hydroxyquinine as compared to healthy controls (N=10). In otherwise healthy subjects with moderate hepatic impairment (Child-Pugh B; N=9) who received a single oral 600 mg dose of quinine sulfate, the mean AUC increased by 55% without a significant change in mean C max, as compared to healthy volunteer controls (N=6). In subjects with hepatitis, the absorption of quinine was prolonged, the elimination half-life was increased, the apparent volume of distribution was higher, but there was no significant difference in weight-adjusted clearance. Therefore, in patients with mild to moderate hepatic impairment, dosage adjustment is not needed, but patients should be monitored closely for adverse effects of quinine [see Use in Specific Populations (8.7)].

In subjects with severe hepatic impairment (Child-Pugh C; N=10), quinine oral clearance (CL/F) was reduced as was formation of the primary 3-hydroxyquinine metabolite. Volume of distribution (Vd/F) was higher and the plasma elimination half-life was increased. Therefore, quinine is not indicated in this population and alternate therapy should be administered [see Dosage and Administration (2.3)].

Drug Interaction Studies
Effect of other drugs on quinine
Quinine is a P-gp substrate and is primarily metabolized by CYP3A4. Other enzymes, including CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP2E1 may contribute to the metabolism of quinine.

Cholestyramine: In 8 healthy subjects who received quinine sulfate 600 mg with or without 8 grams of cholestyramine resin, no significant difference in quinine pharmacokinetic parameters was seen.

Cigarette Smoking (CYP1A2 inducer): In healthy male heavy smokers, the mean quinine AUC following a single 600 mg dose was 44% lower, the mean C max was 18% lower, and the elimination half-life was shorter (7.5 hours versus 12 hours) than in their non-smoking counterparts. However, in malaria patients who received the full 7-day course of quinine therapy, cigarette smoking produced only a 25% decrease in median quinine AUC and a 16.5% decrease in median C max, suggesting that the already reduced clearance of quinine in acute malaria could have diminished the metabolic induction effect of smoking. Because smoking did not appear to influence the therapeutic outcome in malaria patients, it is not necessary to increase the dose of quinine in the treatment of acute malaria in heavy cigarette smokers.

Grapefruit juice (P-gp/CYP3A4 inhibitor): In a pharmacokinetic study involving 10 healthy subjects, the administration of a single 600 mg dose of quinine sulfate with grapefruit juice (full-strength or half-strength) did not significantly alter the pharmacokinetic parameters of quinine. Quinine sulfate capsules may be taken with grapefruit juice.

Histamine H 2-receptor blockers [cimetidine, ranitidine (nonspecific CYP450 inhibitors)]: In healthy subjects who were given a single oral 600 mg dose of quinine sulfate after pretreatment with cimetidine (200 mg three times daily and 400 mg at bedtime for 7 days) or ranitidine (150 mg twice daily for 7 days), the apparent oral clearance of quinine decreased and the mean elimination half-life increased significantly when given with cimetidine but not with ranitidine. Compared to untreated controls, the mean AUC of quinine increased by 20% with ranitidine and by 42% with cimetidine (p<0.05) without a significant change in mean quinine C max[see Drug Interactions (7)].

Isoniazid: Isoniazid 300 mg/day pretreatment for 1 week did not significantly alter the pharmacokinetic parameter values of quinine. Adjustment of quinine sulfate capsules dosage is not necessary when isoniazid is given concomitantly.

Ketoconazole (CYP3A4 inhibitor): In a crossover study, healthy subjects (N=9) who received a single oral dose of quinine hydrochloride (500 mg) concomitantly with ketoconazole (100 mg twice daily for 3 days) had a mean quinine AUC that was higher by 45% and a mean oral clearance of quinine that was 31% lower than after receiving quinine alone [see Drug Interactions (7)].

Macrolide antibiotics (erythromycin, troleandomycin) (CYP3A4 inhibitors): In a crossover study (N=10), healthy subjects who received a single oral 600 mg dose of quinine sulfate with the macrolide antibiotic, troleandomycin (500 mg every 8 hours) exhibited a 87% higher mean quinine AUC, a 45% lower mean oral clearance of quinine, and a 81% lower formation clearance of the main metabolite, 3-hydroxyquinine, than when quinine was given alone [see Drug Interactions (7)].

Erythromycin was shown to inhibit the in vitro metabolism of quinine in human liver microsomes, an observation confirmed by an in vivo interaction study. In a crossover study (N=10), healthy subjects who received a single oral 500 mg dose of quinine sulfate with erythromycin (600 mg every 8 hours for four days) showed a decrease in quinine oral clearance (CL/F), an increase in half-life, and a decreased metabolite (3-hydroxyquinine) to quinine AUC ratio, as compared to when quinine was given with placebo [see Drug Interactions (7)].

Oral contraceptives (estrogen, progestin): In 7 healthy females who were using single-ingredient progestin or combination estrogen-containing oral contraceptives, the pharmacokinetic parameters of a single 600 mg dose of quinine sulfate were not altered in comparison to those observed in 7 age-matched female control subjects not using oral contraceptives.

Rifampin (CYP3A4 inducer): In patients with uncomplicated P. falciparum malaria who received quinine sulfate 10 mg/kg concomitantly with rifampin 15 mg/kg/day for 7 days (N=29), the median AUC of quinine between days 3 and 7 of therapy was 75% lower as compared to those who received quinine monotherapy. In healthy subjects (N=9) who received a single oral 600 mg dose of quinine sulfate after 2 weeks of pretreatment with rifampin 600 mg/day, the mean quinine AUC and C max decreased by 85% and 55%, respectively [see Drug Interactions (7)].

Ritonavir: In healthy subjects who received a single oral 600 mg dose of quinine sulfate with the 15 th dose of ritonavir (200 mg every 12 hours for 9 days), there were 4-fold increases in the mean quinine AUC and C max, and an increase in the mean elimination half-life (13.4 hours versus 11.2 hours), compared to when quinine was given alone [see Drug Interactions (7)].

Tetracycline: In 8 patients with acute uncomplicated P. falciparum malaria who were treated with oral quinine sulfate (600 mg every 8 hours for 7 days) in combination with oral tetracycline (250 mg every 6 hours for 7 days), the mean plasma quinine concentrations were about two-fold higher than in 8 patients who received quinine monotherapy [see Drug Interactions (7)].

Theophylline or aminophylline: In 20 healthy subjects who received multiple doses of quinine sulfate capsules (648 mg every 8 hours x 7 days) with a single 300 mg oral dose of theophylline, the quinine mean C max and AUC were increased by 13% and 14% respectively [see Drug Interactions (7)].

Effects of quinine on other drugs
Results of in vivo drug interaction studies suggest that quinine has the potential to inhibit the metabolism of drugs that are substrates of CYP3A4 and CYP2D6. Quinine inhibits P-gp and has the potential to affect the transport of drugs that are P-gp substrates.

Anticonvulsants (carbamazepine, phenobarbital, and phenytoin): A single 600 mg oral dose of quinine sulfate increased the mean plasma C max, and AUC 0–24 of single oral doses of carbamazepine (200 mg) and phenobarbital (120 mg) but not phenytoin (200 mg) in 8 healthy subjects. The mean AUC increases of carbamazepine, phenobarbital and phenytoin were 104%, 81%, and 4%, respectively; the mean increases in C max were 56%, 53%, and 4%, respectively. Mean urinary recoveries of the three antiepileptics over 24 hours were also profoundly increased by quinine [see Drug Interactions (7)].

Desipramine (CYP2D6 substrate): Quinine (750 mg/day for 2 days) decreased the metabolism of desipramine in patients who were extensive CYP2D6 metabolizers, but had no effect in patients who were poor CYP2D6 metabolizers. Lower doses (80 mg to 400 mg) of quinine did not significantly affect the pharmacokinetics of other CYP2D6 substrates, namely, debrisoquine, dextromethorphan, and methoxyphenamine. Although clinical drug interaction studies have not been performed, antimalarial doses (greater than or equal to 600 mg) of quinine may inhibit the metabolism of other drugs that are CYP2D6 substrates (e.g., flecainide, debrisoquine, dextromethorphan, metoprolol, paroxetine) [see Drug Interactions (7)].

Digoxin (P-gp substrate): In 4 healthy subjects who received digoxin (0.5 to 0.75 mg/day) during treatment with quinine (750 mg/day), a 33% increase in mean steady state AUC of digoxin and a 35% reduction in the steady state biliary clearance of digoxin were observed compared to digoxin alone [see Drug Interactions (7)].

Halofantrine: Although not studied clinically, quinine was shown to inhibit the metabolism of halofantrine in vitro using human liver microsomes. Therefore, concomitant administration of quinine sulfate capsules are likely to increase plasma halofantrine concentrations [see Warnings and Precautions (5.4)].

Mefloquine: In 7 healthy subjects who received mefloquine (750 mg) at 24 hours before an oral 600 mg dose of quinine sulfate, the AUC of mefloquine was increased by 22% compared to mefloquine alone. In this study, the QTc interval was significantly prolonged in the subjects who received mefloquine and quinine sulfate 24 hours apart [see Drug Interactions (7)].

Midazolam (CYP3A4 substrate): In 23 healthy subjects who received multiple doses of quinine sulfate capsules 324 mg three times daily x 7 days with a single oral 2 mg dose of midazolam, the mean AUC and C max of midazolam and 1-hydroxymidazolam were not significantly affected. This finding indicates that 7-day dosing with quinine sulfate capsules 324 mg every 8 hours did not induce the metabolism of midazolam.

Neuromuscular blocking agents (pancuronium, succinylcholine, tubocurarine): In one report, quinine potentiated neuromuscular blockade in a patient who received pancuronium during an operative procedure, and subsequently (3 hours after receiving pancuronium) received quinine 1800 mg daily [see Drug Interactions (7)].

Ritonavir: In healthy subjects who received a single oral 600 mg dose of quinine sulfate with the 15 th dose of ritonavir (200 mg every 12 hours for 9 days), the mean ritonavir AUC, C max, and elimination half-life were slightly but not significantly increased compared to when ritonavir was given alone [see Drug Interactions (7)].

Theophylline or aminophylline (CYP1A2 substrate): In 19 healthy subjects who received multiple doses of quinine sulfate capsules 648 mg every 8 hours x 7 days with a single 300 mg oral dose of theophylline, the mean theophylline AUC was 10% lower than when theophylline was given alone. There was no significant effect on mean theophylline C max[see Drug Interactions (7)].

12.4 Microbiology

Mechanism of Action
Quinine inhibits nucleic acid synthesis, protein synthesis, and glycolysis in P. falciparum and can bind with hemazoin in parasitized erythrocytes. However, the precise mechanism of the antimalarial activity of quinine sulfate is not completely understood.

Antimicrobial Activity
Quinine sulfate acts primarily on the blood schizont form of P. falciparum. It is not gametocidal and has little effect on the sporozoite or pre-erythrocytic forms.

Resistance
Strains of P. falciparum with decreased sensitivity to quinine can be selected in vivo. P. falciparum malaria that is clinically resistant to quinine has been reported in some areas of South America, Southeast Asia, and Bangladesh.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis
Carcinogenicity studies of quinine have not been conducted.

Mutagenesis
Genotoxicity studies of quinine were positive in the Ames bacterial mutation assay with metabolic activation and in the sister chromatid exchange assay in mice. The sex-linked recessive lethal test performed in Drosophila, the in vivo mouse micronucleus assay, and the chromosomal aberration assay in mice and Chinese hamsters were negative.

Impairment of Fertility
In published studies, quinine produced testicular toxicity in mice at a single intraperitoneal dose of 300 mg/kg corresponding to a dose of approximately 0.75 times the maximum recommended human dose (MRHD; 32 mg/kg/day) and in rats at an intramuscular dose of 10 mg/kg/day, 5 days/week, for 8 weeks corresponding to a daily dose of approximately 0.05 times the MRHD based on body surface area (BSA) comparisons. The findings include atrophy or degeneration of the seminiferous tubules, decreased sperm count and motility, and decreased testosterone levels in the serum and testes. There were no changes in testes weight or testicular histopathology in studies of oral doses of up to 500 mg/kg/day in mice and 700 mg/kg/day in rats (approximately 1.2 and 3.5 times the MRHD respectively based on BSA comparisons).