Rx only

Anticonvulsant

Chemical name: 5-ethyldihydro-5-phenyl-4,6 (1H,5H)-pyrimidinedione. Structural formula:

Primidone is a white, crystalline, highly stable substance, M.P. 279 - 284°C. It is poorly soluble in water (60 mg per 100 mL at 37°C) and in most organic solvents. It possesses no acidic properties, in contrast to its barbiturate analog.

Each tablet, for oral administration, contains either 50 mg or 250 mg of primidone. In addition, each tablet contains the following inactive ingredients: lactose monohydrate, methylcellulose, acacia, sodium starch glycolate, and magnesium stearate.

Primidone raises electro- or chemoshock seizure thresholds or alters seizure patterns in experimental animals. The mechanism(s) of primidone's antiepileptic action is not known.

Primidone per se has anticonvulsant activity as do its two metabolites, phenobarbital and phenylethylmalonamide (PEMA). In addition to its anticonvulsant activity, PEMA potentiates the anticonvulsant activity of phenobarbital in experimental animals.

Primidone, used alone or concomitantly with other anticonvulsants, is indicated in the control of grand mal, psychomotor, and focal epileptic seizures. It may control grand mal seizures refractory to other anticonvulsant therapy.

Primidone is contraindicated in: 1) patients with porphyria and 2) patients who are hypersensitive to phenobarbital (see ACTIONS).

The abrupt withdrawal of antiepileptic medication may precipitate status epilepticus. The therapeutic efficacy of a dosage regimen takes several weeks before it can be assessed.

The total daily dosage should not exceed 2 g. Since primidone therapy generally extends over prolonged periods, a complete blood count and a sequential multiple analysis-12 (SMA-12) test should be made every six months.

The most frequently occurring early side effects are ataxia and vertigo. These tend to disappear with continued therapy, or with reduction of initial dosage. Occasionally, the following have been reported: nausea, anorexia, vomiting, fatigue, hyperirritability, emotional disturbances, sexual impotency, diplopia, nystagmus, drowsiness, and morbilliform skin eruptions. Granulocytopenia, agranulocytosis, and red-cell hypoplasia and aplasia, have been reported rarely. These and, occasionally, other persistent or severe side effects may necessitate withdrawal of the drug. Megaloblastic anemia may occur as a rare idiosyncrasy to primidone and to other anticonvulsants. The anemia responds to folic acid without necessity of discontinuing medication.

Adult Dosage

Patients 8 years of age and older who have received no previous treatment may be started on primidone according to the following regimen using either 50 mg or scored 250 mg primidone tablets:

Days 1 to 3: 100 to 125 mg at bedtime.

Days 4 to 6: 100 to 125 mg b.i.d.

Days 7 to 9: 100 to 125 mg t.i.d.

Day 10 to maintenance: 250 mg t.i.d.

For most adults and children 8 years of age and over, the usual maintenance dosage is three to four 250 mg primidone tablets in divided doses (250 mg t.i.d. or q.i.d.). If required, an increase to five or six 250 mg tablets daily may be made but daily doses should not exceed 500 mg q.i.d.

Dosage should be individualized to provide maximum benefit. In some cases, serum blood level determinations of primidone may be necessary for optimal dosage adjustment. The clinically effective serum level for primidone is between 5 to 12 μg/mL.

In Patients Already Receiving Other Anticonvulsants

Primidone should be started at 100 to 125 mg at bedtime and gradually increased to maintenance level as the other drug is gradually decreased. This regimen should be continued until satisfactory dosage level is achieved for the combination, or the other medication is completely withdrawn. When therapy with primidone alone is the objective, the transition from concomitant therapy should not be completed in less than two weeks.

Pediatric Dosage

For children under 8 years of age, the following regimen may be used:

Days 1 to 3: 50 mg at bedtime.

Days 4 to 6: 50 mg b.i.d.

Days 7 to 9: 100 mg b.i.d.

Day 10 to maintenance: 125 mg t.i.d. to 250 mg t.i.d.

For children under 8 years of age, the usual maintenance dosage is 125 to 250 mg three times daily or, 10 to 25 mg/kg/day in divided doses.

Primidone Tablets USP, 50 mg are available as white, round, flat faced, beveled edge, scored tablets debossed LAN over 1301, supplied in bottles of 100, 500 and 1000 tablets.

100 Tablets                    NDC 0527-1301-01

500 Tablets                    NDC 0527-1301-05

1000 Tablets                   NDC 0527-1301-10

Primidone Tablets USP, 250 mg are available as white, round, flat faced, beveled edge, scored tablets debossed LAN over 1231, supplied in bottles of 100, 500 and 1000 tablets.

100 Tablets                    NDC 0527-1231-01

500 Tablets                    NDC 0527-1231-05

1000 Tablets                   NDC 0527-1231-10

Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].

Dispense in a well-closed container as defined in the USP with a child-resistant closure.

Distributed by:
Lannett Company, Inc.
Philadelphia, PA 19136

Dispense with Medication Guide available at: www.lannett.com/med-guide/primidone

CIB70303E
Rev. 06/20

Dispense with Medication Guide available at: www.lannett.com/med-guide/primidone

Primidone Tablets, USP

Read this Medication Guide before you start taking primidone tablets, USP and each time you get a refill. There may be new information. This information does not take the place of talking to your healthcare provider about your medical condition or treatment.

What is the most important information I should know about Primidone Tablets, USP?

Do not stop taking primidone tablets, USP without first talking to your healthcare provider.

Stopping primidone tablets, USP suddenly can cause serious problems.

Primidone tablets, USP can cause serious side effects, including:

1. Like other antiepileptic drugs, primidone tablets, USP may cause suicidal thoughts or actions in a very small number of people, about 1 in 500.

Call a healthcare provider right away if you have any of these symptoms, especially if they are new, worse, or worry you:

• thoughts about suicide or dying
• attempts to commit suicide
• new or worse depression
• new or worse anxiety
• feeling agitated or restless
• panic attacks
• trouble sleeping (insomnia)
• new or worse irritability
• acting aggressive, being angry, or violent
• acting on dangerous impulses
• an extreme increase in activity and talking (mania)
• other unusual changes in behavior or mood

How can I watch for early symptoms of suicidal thoughts and actions?

• Pay attention to any changes, especially sudden changes, in mood, behaviors, thoughts, or feelings.
• Keep all follow-up visits with your healthcare provider as scheduled.

Call your healthcare provider between visits as needed, especially if you are worried about symptoms.

Do not stop primidone tablets, USP without first talking to a healthcare provider.

• Stopping primidone tablets, USP suddenly can cause serious problems. Stopping a seizure medicine suddenly in a patient who has epilepsy can cause seizures that will not stop (status epilepticus).

Suicidal thoughts or actions can be caused by things other than medicines. If you have suicidal thoughts or actions, your healthcare provider may check for other causes.

What is Primidone Tablets, USP?

Primidone tablets, USP is a prescription medicine used alone or with other medicines to treat people with:

• generalized tonic-clonic (grand mal) seizures
• complex partial (psychomotor) seizures
• partial (focal) epileptic seizures.

Who should not take Primidone Tablets, USP?

Do not take primidone tablets, USP if you:

• have a genetic disorder called porphyria
• are allergic to phenobarbital

What should I tell my healthcare provider before taking Primidone Tablets, USP?

Before you take primidone tablets, USP, tell your healthcare provider if you:

• have or have had depression, mood problems or suicidal thoughts or behavior
• have any other medical conditions
• are pregnant or planning to become pregnant. Primidone tablets, USP may harm your unborn baby. Tell your healthcare provider right away if you become pregnant while taking primidone tablets, USP. You and your healthcare provider will decide if you should take primidone tablets, USP while you are pregnant.
  • If you become pregnant while taking primidone tablets, USP, talk to your healthcare provider about registering with the North American Antiepileptic Drug (NAAED) Pregnancy Registry. You can enroll in this registry by calling 1-888-233-2334. The purpose of this registry is to collect information about the safety of antiepileptic drugs during pregnancy.
• are breastfeeding or plan to breastfeed. Primidone tablets, USP can pass into breast milk. Talk to your healthcare provider about the best way to feed your baby if you take primidone tablets, USP.

Tell your healthcare provider about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Taking primidone tablets, USP with certain other medicines can cause side effects or affect how well they work. Do not start or stop other medicines without talking to your healthcare provider.

Know the medicines you take. Keep a list of them and show it to your healthcare provider and pharmacist each time you get a new medicine.

How should I take Primidone Tablets, USP?

Take primidone tablets, USP exactly as prescribed. Your healthcare provider will tell you how much primidone tablets, USP to take and when to take it.

• Your healthcare provider may change your dose. Do not change your dose without talking to your healthcare provider.
• Do not stop taking primidone tablets, USP without first talking to your healthcare provider. Stopping primidone tablets, USP suddenly can cause serious problems.
• If you take too much primidone tablets, USP, call your healthcare provider or local Poison Control Center right away.

What should I avoid while taking Primidone Tablets, USP?

• Primidone tablets, USP can make you sleepy or dizzy. Do not drink alcohol or take other drugs that make you sleepy or dizzy while taking primidone tablets, USP without first discussing this with your healthcare provider. Taking primidone tablets, USP with alcohol or drugs that cause sleepiness or dizziness may make your sleepiness or dizziness worse.
• Do not drive, operate heavy machinery, or do other dangerous activities until you know how primidone tablets, USP affects you. Primidone tablets, USP can slow your thinking and motor skills.

What are the possible side effects of Primidone Tablets, USP?

See "What is the most important information I should know about Primidone Tablets, USP?".

Primidone tablets, USP may cause other serious side effects including:

• Sleepiness that can be severe, especially when you first start taking primidone tablets, USP.
• Primidone tablets, USP may rarely cause blood problems. Symptoms may include:
  • fever, swollen glands, or sore throat that come and go or do not go away
  • Frequent infections or an infection that does not go away
  • tiredness
  • shortness of breath
• Primidone tablets, USP may rarely cause allergic reactions. Symptoms may include:
  • skin rash
  • hives
  • sores in your mouth
  • blistering or peeling skin

The most common side effects of primidone tablets, USP include:

• problems with walking and moving
• feelings of dizziness, spinning, or swaying (vertigo)

These are not all the possible side effects of primidone tablets, USP. For more information, ask your healthcare provider or pharmacist.

Tell your healthcare provider if you have any side effect that bothers you or that does not go away.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

How should I store Primidone Tablets, USP?

Store primidone tablets, USP at room temperature between 68°F to 77°F (20°C to 25°C) in a well-closed container.

Keep primidone tablets, USP and all medicines out of the reach of children.

General Information about Primidone Tablets, USP

Medicines are sometimes prescribed for purposes other than those listed in a Medication Guide. Do not use primidone tablets, USP for a condition for which it was not prescribed. Do not give primidone tablets, USP to other people, even if they have the same symptoms that you have. It may harm them.

This Medication Guide summarizes the most important information about primidone tablets, USP. If you would like more information, talk with your healthcare provider. You can ask your pharmacist or healthcare provider for information about primidone tablets, USP that is written for health professionals.

For more information, call Lannett Company, Inc. at 1-844-834-0530.

What are the ingredients in Primidone Tablets, USP?

Active Ingredient: primidone

Inactive ingredients: lactose monohydrate, acacia, methylcellulose, magnesium stearate, and sodium starch glycolate

Distributed by:
Lannett Company, Inc.
Philadelphia, PA 19136

This Medication Guide has been approved by the U.S. Food and Drug Administration

CIB70304E
Rev. 06/20

NDC 0527-1301-01

Primidone
Tablets, USP

50 mg

Print Medication Guide at:
www.lannett.com/med-guide/primidone

Rx Only

100 Tablets

Lannett

NDC 0527-1231-01

Primidone
Tablets, USP

250 mg

Print Medication Guide at:
www.lannett.com/med-guide/primidone

Rx Only

100 Tablets

Lannett