Clonazepam

Action

Unknown. May enhance activity of gamma-aminobutyric acid, an inhibitory neurotransmitter in CNS.

Availability

Tablets: 0.5 mg, 1 mg, 2 mg

Indications and dosages

➣ Absence seizures (Lennox-Gastaut syndrome); akinetic and myoclonic seizures

Adults: Initially, 1.5 mg/day P.O. in three divided doses; may increase by 0.5 to 1 mg q 3 days until seizures are adequately controlled or drug intolerance occurs. Maximum dosage is 20 mg/day.

Infants and children ages 10 and younger or weighing 30 kg (66 lb) or

less: Initially, 0.01 to 0.03 mg/kg/day P.O. Give total dosage (not to exceed 0.05 mg/kg/day) in two to three equally divided doses. Increase by no more than 0.25 to 0.5 mg q 3 days until dosage of 0.1 to 0.2 mg/kg/day is reached, seizures are adequately controlled, or drug intolerance occurs.

Off-label uses

• Acute manic episodes of bipolar disorder

• Multifocal tic disorders

• Neuralgias

• Parkinsonian dysarthria

• Periodic leg movements occurring during sleep

• Adjunctive treatment of schizophrenia

Contraindications

• Hypersensitivity to drug or other benzodiazepines

• Severe hepatic disease

• Acute angle-closure glaucoma

Precautions

Use cautiously in:

• renal impairment, chronic respiratory disease, open-angle glaucoma

• history of porphyria

• pregnant or breastfeeding patients

• children.

Administration

☞ Be aware that overdose may cause fatal respiratory depression or cardiovascular collapse.

• Give tablets with water, and make sure patient swallows them whole.

Adverse reactions

CNS: ataxia, fatigue, drowsiness, behavioral changes, depression, dizziness, nervousness, reduced intellectual ability

CV: palpitations

EENT: abnormal eye movements, blurred vision, diplopia, nystagmus, sinusitis, rhinitis, pharyngitis

GI: constipation, diarrhea, hypersalivation

GU: dysuria, nocturia, urinary retention, dysmenorrhea, delayed ejaculation, erectile dysfunction

Hematologic: anemia, eosinophilia,

leukopenia, thrombocytopenia

Hepatic: hepatitis

Musculoskeletal: myalgia

Respiratory: increased respiratory secretions, upper respiratory tract infection, cough, bronchitis, respiratory depression

Other: appetite changes, fever, physical or psychological drug dependence, drug tolerance, allergic reaction

Interactions

Drug-drug. Antidepressants, antihistamines, opioids, other benzodiazepines: additive CNS depression

Barbiturates, rifampin: increased metabolism and decreased efficacy of clonazepam

Cimetidine, disulfiram, fluoxetine, hormonal contraceptives, isoniazid, ketoconazole, metoprolol, propoxyphene, propranolol, valproic acid: decreased clonazepam metabolism

Phenytoin: decreased clonazepam blood level

Drug-diagnostic tests. Eosinophils, liver function tests: increased values

Platelets, white blood cells: decreased counts

Drug-herbs. Chamomile, hops, kava, skullcap, valerian: increased CNS depression

Drug-behaviors. Alcohol use: increased CNS depression

Patient monitoring

• Monitor patient for respiratory depression. Assess respiratory rate and quality, oxygen saturation (using pulse oximetry), and mental status.

• Monitor hematologic and liver function test results.

Patient teaching

☞ Instruct patient to immediately report easy bleeding or bruising or yellowing of skin or eyes.

• Advise patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.

☞ Caution patient not to stop taking drug abruptly. Advise him to consult prescriber for dosage-tapering schedule if he wishes to discontinue drug.

• Advise patient not to drink alcohol, which may increase drowsiness, dizziness, and risk of seizures.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.