2.1 Dosing Information

The usual lofexidine tablet starting dosage is three 0.18 mg tablets taken orally 4 times daily during the period of peak withdrawal symptoms (generally the first 5 to 7 days following last use of opioid) with dosing guided by symptoms and side effects. There should be 5 to 6 hours between each dose. The total daily dosage of lofexidine tablets should not exceed 2.88 mg (16 tablets) and no single dose should exceed 0.72 mg (4 tablets).
Lofexidine tablet treatment may be continued for up to 14 days with dosing guided by symptoms.
Discontinue lofexidine tablets with a gradual dose reduction over a 2- to 4-day period to mitigate lofexidine tablet withdrawal symptoms (e.g., reducing by 1 tablet per dose every 1 to 2 days) [see Warnings & Precautions (5.5)].The lofexidine tablet dose should be reduced, held, or discontinued for individuals who demonstrate a greater sensitivity to lofexidine tablets side effects [see Warnings and Precautions (5.1), Adverse Reactions (6.1)].  Lower doses may be appropriate as opioid withdrawal symptoms wane.
Lofexidine tablets can be administered in the presence or absence of food.

2.2 Dosage Recommendations for Patients with Hepatic Impairment

Recommended dosage adjustments based on the degree of hepatic impairment are shown in Table 1. [see Use in Specific Populations(8.6),Clinical Pharmacology (12.3)].

Table 1: Dosage Recommendations in Patients with Hepatic Impairment

2.3 Dosage Recommendations for Patients with Renal Impairment

Recommended dosage adjustments based on the degree of renal impairment are shown in Table 2. Lofexidine tablets may be administered without regard to the timing of dialysis [see Use in Specific Populations (8.7), Clinical Pharmacology (12.3)].

Table 2: Dosage Recommendations in Patients with Renal Impairment

5.1 Risk of Hypotension, Bradycardia, and Syncope

Lofexidine can cause a decrease in blood pressure, a decrease in pulse, and syncope [see Adverse Reactions (6.1), Clinical Pharmacology (12.2)]. Monitor vital signs before dosing. Monitor symptoms related to bradycardia and orthostasis.
Patients being given lofexidine in an outpatient setting should be capable of and instructed on self-monitoring for hypotension, orthostasis, bradycardia, and associated symptoms. If clinically significant or symptomatic hypotension and/or bradycardia occur, the next dose of lofexidine should be reduced in amount, delayed, or skipped.
Inform patients that lofexidine may cause hypotension and that patients moving from a supine to an upright position may be at increased risk for hypotension and orthostatic effects. Instruct patients to stay hydrated, on how to recognize symptoms of low blood pressure, and on how to reduce the risk of serious consequences should hypotension occur (e.g., sit or lie down, carefully rise from a sitting or lying position). Instruct outpatients to withhold lofexidine doses when experiencing symptoms of hypotension or bradycardia and to contact their health care provider for guidance on how to adjust dosing.
Avoid using lofexidine in patients with severe coronary insufficiency, recent myocardial infarction, cerebrovascular disease, chronic renal failure, and in patients with marked bradycardia.
Avoid using lofexidine in combination with medications that decrease pulse or blood pressure to avoid the risk of excessive bradycardia and hypotension.

5.2 Risk of QT Prolongation

Lofexidine prolong the QT interval.
Avoid using lofexidine in patients with congenital long QT syndrome.
Monitor ECG in patients with congestive heart failure, bradyarrhythmias, hepatic impairment, renal impairment, or patients taking other medicinal products that lead to QT prolongation (e.g., methadone). In patients with electrolyte abnormalities (e.g., hypokalemia or hypomagnesemia), correct these abnormalities first, and monitor ECG upon initiation of lofexidine [see Dosing and Administration (2.1), Adverse Reactions (6.1), Special Populations (8.6, 8.7),Clinical Pharmacology (12.2)].

5.3 Increased Risk of Central Nervous System Depression with Concomitant use of CNS Depressant Drugs

Lofexidine potentiate the CNS depressive effects of benzodiazepines and can also be expected to potentiate the CNS depressive effects of alcohol, barbiturates, and other sedating drugs. Advise patients to inform their healthcare provider of other medications they are taking, including alcohol.
Advise patients using lofexidine in an outpatient setting that, until they learn how they respond to Lofexidine, they should be careful or avoid doing activities such as driving or operating heavy machinery.

5.4 Increased Risk of Opioid Overdose after Opioid Discontinuation

Lofexidine is not a treatment for opioid use disorder. Patients who complete opioid discontinuation are likely to have a reduced tolerance to opioids and are at increased risk of fatal overdose should they resume opioid use. Use lofexidine in patients with opioid use disorder only in conjunction with a comprehensive management program for the treatment of opioid use disorder and inform patients and caregivers of this increased risk of overdose.

5.5 Risk of Discontinuation Symptoms

Stopping lofexidine abruptly can cause a marked rise in blood pressure. Symptoms including diarrhea, insomnia, anxiety, chills, hyperhidrosis, and extremity pain have also been observed with lofexidine discontinuation. Instruct patients not to discontinue therapy without consulting their healthcare provider. When discontinuing therapy with lofexidine tablets, gradually reduce the dose [see Dosing and Administration (2.1)].
Symptoms related to discontinuation can be managed by administration of the previous lofexidine dose and subsequent taper.

6.1 Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to adverse reaction rates observed for another drug and may not reflect the rates observed in practice.
The safety of lofexidine was supported by three randomized, double-blind, placebo-controlled clinical trials, an open-label study, and clinical pharmacology studies with concomitant administration of either methadone, buprenorphine, or naltrexone.
The three randomized, double-blind, placebo-controlled clinical trials enrolled 935 subjects dependent on short-acting opioids undergoing abrupt opioid withdrawal. Patients were monitored before each dose in an inpatient setting.
Table 3 presents the incidence, rounded to the nearest percent, of adverse events that occurred in at least 10% of subjects treated with lofexidine and for which the incidence in patients treated with lofexidine were greater than the incidence in subjects treated with placebo in a study that tested two doses of lofexidine, 2.16 mg per day and 2.88 mg per day, and placebo. The overall safety profile in the combined dataset was similar.
Orthostatic hypotension, bradycardia, hypotension, dizziness, somnolence, sedation, and dry mouth were notably more common in subjects treated with lofexidine than subjects treated with placebo.
Table 3: Adverse Reactions Reported by ≥10% of Lofexidine-Treated Patients and More Frequently than Placebo
                                                        

1 Assigned dose; mean average daily dose received was 79% of assigned dose due to dose-holds for out-of-range vital signs.
Other notable adverse reactions associated with the use of lofexidine but reported in <10% of patients in the lofexidine group included:

• Syncope: 0.9%, 1.4% and 0% for lofexidine 2.16 mg/day and 2.88 mg/day and placebo, respectively
• Tinnitus: 0.9%, 3.2% and 0% for lofexidine 2.16 mg/day and 2.88 mg/day and placebo, respectively

Blood pressure changes and adverse reactions after lofexidine cessation
Elevations in blood pressure above normal values (≥ 140 mmHg systolic) and above a subject’s pre-treatment baseline are associated with discontinuing lofexidine, and peaked on the second day after discontinuation, as shown in Table 4. Blood pressure values were evaluated for 3 days following the last dose of a 5-day course of lofexidine 2.88 mg/day.
Table 4: Blood Pressure Elevations after Stopping Treatment

Blood pressure elevations of a similar magnitude and incidence were observed in a small number of patients (N=10) that had a one-day, 50% dose reduction prior to discontinuation.
After stopping treatment, subjects who were taking lofexidine also had a higher incidence of diarrhea, insomnia, anxiety, chills, hyperhidrosis, and extremity pain compared to subjects who were taking placebo.
Sex-specific adverse event findings
Four out of 101 females (4%) had serious cardiovascular adverse events compared to 3 out of 289 (1%)  males assigned to receive lofexidine 2.88 mg/day.
Discontinuations and dose-holds due to bradycardia and orthostatic hypotension, which are the most common adverse reactions associated with lofexidine, occurred with a greater incidence in females assigned to receive the highest studied dose of lofexidine, 2.88 mg/day as shown in Table 5.
Table 5: Discontinuations and Dose-Holds for Bradycardia and Orthostatic Hypotension by Lofexidine Dose and Sex

6.2 Postmarketing Experience

Lofexidine is marketed in other countries for relief of opioid withdrawal symptoms. The following events have been identified during postmarketing use of lofexidine. Because these reactions are 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.
Since lofexidine’s initial market introduction in 1992, the most frequently reported postmarketing adverse event with lofexidine has been hypotension [see Warnings and Precautions (5.1)]. There has been one report of QT prolongation, bradycardia, torsades de pointes, and cardiac arrest with successful resuscitation in a patient who received lofexidine, and three reports of clinically significant QT prolongation in subjects concurrently receiving methadone with lofexidine.

7.1 Methadone

Lofexidine and methadone both prolong the QT interval. ECG monitoring is recommended in patients receiving methadone and lofexidine concomitantly [see Warnings and Precautions (5.2), Clinical Pharmacology (12.3)].

7.2 Oral Naltrexone

Coadministration of lofexidine and oral naltrexone resulted in statistically significant differences in the steady-state pharmacokinetics of naltrexone. It is possible that oral naltrexone efficacy may be reduced if used concomitantly within 2 hours of lofexidine. This interaction is not expected if naltrexone is administered by non-oral routes[see Clinical Pharmacology (12.3)].

7.3 CNS Depressant Drugs

Lofexidine potentiate the CNS depressant effects of benzodiazepines and may potentiate the CNS depressant effects of alcohol, barbiturates, and other sedating drugs. Advise patients to inform their healthcare provider of other medications they are taking, including alcohol [see Warnings and Precautions (5.3)].

7.4 CYP2D6 Inhibitor - Paroxetine

Coadministration of lofexidine and paroxetine resulted in a 28% increase in the extent of absorption of lofexidine. Monitor for orthostatic hypotension and bradycardia when an inhibitor of CYP2D6 is used concomitantly with lofexidine[see Clinical Pharmacology (12.3)].

8.1 Pregnancy

Risk Summary
The safety of lofexidine in pregnant women has not been established. In animal reproduction studies, oral administration of lofexidine during organogenesis to pregnant rats and rabbits caused a reduction in fetal weights, increases in fetal resorptions, and litter loss at exposures below that in humans. When oral lofexidine was administered from the beginning of organogenesis through lactation, increased stillbirths and litter loss were noted along with decreased viability and lactation indices. The offspring exhibited delays in sexual maturation, auditory startle, and surface righting. These effects occurred at exposures below that in humans [see Animal Data].
The background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies carry some risk of birth defect, loss, or other adverse outcomes. The background risk of major birth defects in the U.S. general population is 2% to 4% and of miscarriage is 15% to 20% of clinically recognized pregnancies.
Data
Animal Data
Increased incidence of resorptions, decreased number of implantations, and a concomitant reduction in the number of fetuses were observed when pregnant rabbits were orally administered lofexidine hydrochloride during organogenesis (from gestation day [GD] 7 to 19) at a daily dose of 5.0 mg/kg/day (approximately 0.08 times the maximum recommended human dose [MRHD] of 2.88 mg lofexidine base on an AUC basis). Maternal toxicity evidenced by increased mortality was noted at the highest tested dose of 15 mg/kg/day (approximately 0.4 times the MRHD on an AUC basis).
Decreased implantations per dam and decreased mean fetal weights were noted in a study in which pregnant rats were treated with oral lofexidine hydrochloride during organogenesis (from GD 7 to 16) at a daily dose of 3.0 mg/kg/day (approximately 0.9 times the MRHD on an AUC basis). This dose was associated with maternal toxicity (decreased body weight gain and mortality). No malformations or evidence of developmental toxicity were evident at 1.0 mg/kg/day (approximately 0.2 times the MRHD on an AUC basis).
A dose-dependent increase in pup mortality was noted in all doses of lofexidine hydrochloride administered orally to pregnant rats from GD 6 through lactation at an exposure less than the human exposure based on AUC comparisons. Doses higher than 1.0 mg/kg/day (approximately 0.2 times the MRHD on an AUC basis) resulted in incidences of total litter loss and maternal toxicity (piloerection and decreased body weight gain). At the highest dose tested of 2.0 mg/kg/day (approximately 0.6 times the MRHD on an AUC basis), increased stillbirths as well as decreased viability and lactation indices were reported. Surviving offspring exhibited lower body weights, developmental delays, and increased delays in auditory startle at doses of 1.0 mg/kg/day or higher. Sexual maturation was delayed in male offspring (preputial separation) at 2.0 mg/kg/day and in female offspring (vaginal opening) at 1.0 mg/kg/day or higher.

8.2 Lactation

Risk Summary
There is no information regarding the presence of lofexidine or its metabolites in human milk, the effects on the breastfed infant, or the effects on milk production. Caution should be exercised when lofexidine is administered to a nursing woman.
The developmental and health benefits should be considered along with the mother’s clinical need for lofexidine and any other potential adverse effects on breastfed children from lofexidine or from the underlying maternal condition.

8.3 Females and Males of Reproductive Potential

In animal studies that included some fertility endpoints, lofexidine decreased breeding rate and increased resorptions at exposures below human exposures. The impact of lofexidine on male fertility has not been adequately characterized in animal studies [see Impairment of Fertility (13.1)].

8.4 Pediatric Use

The safety and effectiveness of lofexidine have not been established in pediatric patients.

8.5 Geriatric Use

No studies have been performed to characterize the pharmacokinetics of lofexidine or to establish its safety and effectiveness in geriatric patients. Caution should be exercised when lofexidine is administered to patients over 65 years of age. Dosing adjustments similar to those recommended in patients with renal impairment should be considered [see Dosage and Administration (2.3), Use in Specific Populations (8.7)].

8.6 Hepatic Impairment

Hepatic impairment slows the elimination of lofexidine but exhibits less effect on the peak plasma concentration than on AUC values following a single dose. Dosage adjustments are recommended based on the degree of hepatic impairment. [see Dosage and Administration (2.2), Clinical Pharmacology (12.3)].
Clinically relevant QT prolongation may occur in subjects with hepatic impairment [see Warnings and Precautions (5.2), Clinical Pharmacology (12.2)].

8.7 Renal Impairment

Renal impairment slows the elimination of lofexidine but exhibits less effect on the peak plasma concentration than on AUC values following a single dose. Dosage adjustments are recommended based on the degree of renal impairment[see Dosage and Administration (2.3), Clinical Pharmacology (12.3)].
Only a negligible fraction of the lofexidine dose is removed during a typical dialysis session, so no additional dose needs to be administered after a dialysis session; lofexidine may be administered without regard to the timing of dialysis [see Dosage and Administration (2.3), Clinical Pharmacology (12.3)].
Clinically relevant QT prolongation may occur in subjects with renal impairment[see Warnings and Precautions (5.2), Clinical Pharmacology (12.2)].

8.8 CYP2D6 Poor Metabolizers

Although the pharmacokinetics of lofexidine have not been systematically evaluated in patients who do not express the drug metabolizing enzyme CYP2D6, it is likely that the exposure to lofexidine would be increased similarly to taking strong CYP2D6 inhibitors (approximately 28%). Monitor adverse events such as orthostatic hypotension and bradycardia in known CYP2D6 poor metabolizers. Approximately 8% of Caucasians and 3 to 8% of Black/African Americans cannot metabolize CYP2D6 substrates and are classified as poor metabolizers (PM) [see Clinical Pharmacology (12.3)].

12.1 Mechanism of Action

Lofexidine is a central alpha-2 adrenergic agonist that binds to receptors on adrenergic neurons. This reduces the release of norepinephrine and decreases sympathetic tone.

12.2 Pharmacodynamics

Cardiac Electrophysiology
Single lofexidine doses of 1.44 mg to 1.8 mg produced maximum mean change from baseline in QTcF (ΔQTcF) of 14.4 msec (upper two-sided 90% CI: 22.3 msec) and 13.6 msec (17.4 msec) for 1.44 mg and 1.8 mg respectively in healthy normal volunteers.
In a Phase 3 placebo-controlled, dose response study in opioid dependent subjects, lofexidine was associated with a maximum mean prolongation of the QTcF interval 7.3 (8.8) msec and 9.3 (10.9) msec at doses of 2.16 mg/day and 2.88 mg/day, respectively.
Patients with hepatic impairment
Administration of lofexidine to subjects with hepatic impairment was associated with prolongation of the QTc interval, which was more pronounced in subjects with severe hepatic impairment [see Use in Specific Populations (8.6)].
Patients with renal impairment
Administration of lofexidine to subjects with renal impairment was associated with prolongation of the QTc interval, which was more pronounced in subjects with severe renal impairment [see Use in Specific Populations (8.7)].
Lofexidine coadministered with methadone
Lofexidine (2.88 mg/day) coadministered with methadone in 18 methadone-maintained patients (80 to 120 mg/day) resulted in a maximum mean increase from methadone-alone baseline in QTcF of 9.1 (14.2) msec.
Lofexidine coadministered with buprenorphine
Lofexidine (2.88 mg/day) coadministered with buprenorphine in 21 buprenorphine-maintained patients (16 to 24 mg/day) resulted in a maximum mean QTcF increase of 1.5 (5.6) msec compared to a buprenorphine-alone baseline.
In Vitro Binding
Lofexidine exhibits in vitro binding affinity and functional agonist activity with alpha-2A and alpha-2C adrenoreceptors at concentrations within clinical exposure plasma levels (Ki values of approximately 7.2 nM and 12 nM, and EC50 values of 4.9 nM and 0.9 nM, respectively).

12.3 Pharmacokinetics

Absorption
Lofexidine is well absorbed and achieves peak plasma concentration 3 to 5 hours after administration of a single dose.
Lofexidine shows approximately dose-proportional pharmacokinetics. Administration of lofexidine with food does not alter its pharmacokinetics.
The absolute bioavailability of a single oral lofexidine dose (0.36 mg in solution) compared with an intravenous infusion (0.2 mg infused for 200 minutes) was 72%. Mean lofexidine Cmax after the oral dose and intravenous infusion was 0.82 ng/mL (at median Tmax of 3 hours) and 0.64 ng/mL (at median Tmax of 4 hours), respectively. Mean estimates of overall systemic exposure (AUCinf) were 14.9 ng•h/mL and 12.0 ng•h/mL, respectively.
Distribution
Mean lofexidine apparent volume of distribution and volume of distribution values following the administration of an oral dose and an intravenous dose were 480.0 L and 297.9 L, respectively, which are appreciably greater than total body volume, suggesting extensive lofexidine distribution into body tissue.
Lofexidine protein binding is approximately 55%.
Lofexidine is not preferentially taken up by blood cells. In a study comparing lofexidine concentrations in plasma and whole blood at the time of peak lofexidine concentrations in human volunteers, it was determined that red blood cells contain approximately 27% the lofexidine concentration of the plasma.
Elimination
Metabolism
From absolute bioavailability results, approximately 30% of the administered lofexidine dose is converted to inactive metabolites during the first pass effect associated with drug absorption from the gut.
Lofexidine and its major metabolites did not induce or inhibit any CYP450 isoforms, with the exception of a slight inhibition of CYP2D6 by lofexidine, with an IC50 of 4551 nM (approximately 225 times the steady-state Cmax for lofexidine with 0.72 mg 4 times daily dosing). Any lofexidine interaction with CYP2D6 substrates is not expected to be clinically significant.
Lofexidine is metabolized when incubated in vitro with human liver microsomes, the major contributor to the hepatic metabolism of lofexidine is CYP2D6, with CYP1A2 and CYP2C19 also capable of metabolizing lofexidine.
Excretion
The elimination half-life is approximately 12 hours and mean clearance is 17.6 L/h following an IV infusion.
Lofexidine has a terminal half-life of approximately 11 to 13 hours following the first dose. At steady-state, the terminal half-life is approximately 17 to 22 hours. Accumulation occurs up to 4 days with repeat dosing, following the recommended dosing regimen.
A mass balance study of lofexidine showed nearly complete recovery of radiolabel in urine (93.5%) over 144 hours postdose, with an additional 0.92% recovered in the feces over 216 hours postdose. Thus, it appears that all, or nearly all, of the dose was absorbed, and that the primary route of elimination of the parent drug and its metabolites is via the kidney. Renal elimination of unchanged drug accounts for approximately 15% to 20% of the administered dose.
Specific Populations
Hepatic Impairment
Hepatic impairment slows the elimination of lofexidine but exhibits less effect on the peak plasma concentration following a single dose. In a study comparing the pharmacokinetics of lofexidine (0.36 mg) in mild, moderate, and severe hepatically impaired subjects to subjects with normal hepatic function (6 subjects in each hepatic function group), mean Cmax values were similar for subjects with normal, mild, and moderate hepatic impairment as shown in Table 6.
Table 6: Lofexidine Pharmacokinetics in Subjects with Hepatic Impairment
                                            

Renal Impairment
Renal impairment slows the elimination of lofexidine but exhibits less effect on the peak plasma concentration following a single dose. In a study comparing the pharmacokinetics of lofexidine (0.36 mg) in 8 end-stage renal disease subjects on 3 times weekly hemodialysis to 8 subjects with normal renal function matched for sex, age, and body mass index, mean Cmax values were similar for end-stage renal disease and normal renal function subjects, indicating no change in maximum lofexidine exposure with renal impairment as shown in Table 7.
The impact of dialysis on the overall pharmacokinetics of lofexidine during a typical 4-hour dialysis was minimal; the drop in lofexidine plasma concentrations produced during the dialysis session was transient, with a rebound to nearly predialysis concentrations after re-equilibration within a few hours following completion of the dialysis cycle [see Dosage and Administration (2.3), Use in Specific Populations (8.7)].
In a study comparing the pharmacokinetics of lofexidine (0.36 mg) in 6 subjects each with normal renal function, mild renal impairment, and moderate renal impairment as well as 5 subjects with severe renal impairment but not requiring dialysis, there were similar increases in mean Cmax values in subjects with mild and moderate renal impairment in comparison to subjects with normal renal function with additional increases in mean Cmax values in subjects with severe renal impairment. Mean AUClast, AUC∞, and t1/2 increased with severity of renal impairment as shown in Table 7.
Table 7: Lofexidine Pharmacokinetics in Subjects with Renal Impairment
                                                  

Drug Interaction Studies
Lofexidine coadministered with methadone
In a double-blind placebo-controlled study of 23 patients maintained on methadone (80 to 120 mg/day) concomitantly administered lofexidine up to 2.88 mg/day, lofexidine did not alter the pharmacokinetics of methadone. Lofexidine concentrations may be slightly increased when coadministered with methadone; however, the increase at concentrations expected with recommended dosing is not clinically meaningful[see Drug Interactions (7.1)].
Lofexidine coadministered with buprenorphine
In a double-blind placebo-controlled study of 30 subjects maintained on buprenorphine (16 to 24 mg/day) concomitantly administered lofexidine up to 2.88 mg/day, no pharmacokinetic or pharmacodynamic interactions between lofexidine and buprenorphine were seen.
Lofexidine coadministered with oral naltrexone
In an open-label, single-arm study of 24 healthy subjects, oral naltrexone (50 mg/day) did not significantly alter the single-dose pharmacokinetics of lofexidine (0.36 mg). The alteration in steady-state pharmacokinetics of oral naltrexone was statistically significant in the presence of lofexidine. The Tmax was delayed for both naltrexone and 6ß-naltrexol (2 to 3 hours), and overall exposure was slightly reduced when naltrexone was administered with lofexidine[see Drug Interactions (7.2)].
Lofexidine coadministered with paroxetine
In an open-label, single-sequence study of 24 healthy subjects, the strong CYP2D6 inhibitor paroxetine (40 mg/day) increased lofexidine (0.36 mg) Cmax and AUC∞ by approximately 11% and 28%, respectively [see Drug Interactions (7.4)].

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis
No adequate long-term animal studies have been completed to evaluate the carcinogenic potential of lofexidine.
Mutagenesis
Lofexidine tested positive in the in vitro mouse lymphoma assay. Lofexidine tested negative in the in vitro bacterial reverse mutation assay (Ames assay) and in the in vivo rat micronucleus assay.
Impairment of Fertility
In a female fertility study in rabbits, fertility was not adversely impacted by administration of lofexidine hydrochloride up to 6.4 mg/kg/day (approximately 0.1 times the MRHD of 2.88 mg on an AUC basis) when administered orally starting 2 weeks prior to mating and through gestation and lactation. However, decreased breeding rate and higher post-implantation loss was observed at this dose, which correlated with higher resorptions and reduced litter size. Maternal toxicity, which included increased mortality rate, reduced body weight gain, and moderate sedation was observed at 6.4 mg/kg/day. The NOAEL for female fertility was 6.4 mg/kg/day and the NOAEL for female-mediated developmental parameters was 0.4 mg/kg/day (approximately 0.005 times the MRHD on an AUC basis).
In a fertility study in rats, fertility was unaffected by administration of lofexidine up to 0.88 mg/kg/day (approximately 0.2 times the MRHD on an AUC basis) via diet to male and female rats prior to mating and to the dams through gestation and lactation. No evidence of maternal toxicity was observed. However, no assessment of sperm or reproductive organs were performed in this study.
Reduced testes, epididymis, and seminiferous tubule weights, as well as delayed sexual maturation of males and females and decreases in the number of corpora lutea and implantations after mating, were noted in offspring of pregnant rats administered lofexidine hydrochloride orally from GD 6 through lactation at exposures less than the human exposure based on AUC comparisons.