modafinil

Action

Unknown. Thought to stimulate CNS by decreasing the release of gamma-aminobutyric acid (a CNS depressant), thereby increasing mental alertness.

Availability

Tablets: 100 mg, 200 mg

Indications and dosages

➣ Narcolepsy

Adults: 200 mg/day P.O. as a single dose in morning

Dosage adjustment

• Severe hepatic impairment

Contraindications

• Hypersensitivity to drug

Precautions

Use cautiously in:

• recent myocardial infarction, unstable angina, severe hepatic impairment, hyperthyroidism, hypertension, glaucoma, anxiety

• history of left ventricular hypertrophy, ischemic ECG changes, chest pain, arrhythmias, or mitral valve prolapse with previous CNS stimulant use

• history of psychosis

• drug abuse

• pregnant or breastfeeding patients

• children (safety and efficacy not established).

Administration

• Give without food (food delays drug absorption).

Adverse reactions

CNS: headache, dizziness, nervousness, insomnia, depression, anxiety, amnesia, tremor, emotional lability

CV: hypertension, chest pain, vasodilation, hypotension, syncope, arrhythmias

EENT: abnormal vision, amblyopia, epistaxis, rhinitis, pharyngitis

GI: nausea, vomiting, diarrhea, dry mouth, anorexia

GU: abnormal urine, urinary retention, albuminuria, abnormal ejaculation

Hematologic: eosinophilia

Metabolic: hyperglycemia

Musculoskeletal: joint disorders, neck pain and rigidity

Respiratory: lung disorder, dyspnea, asthma

Skin: dry skin

Other: fever, chills, herpes simplex infection

Interactions

Drug-drug. Carbamazepine, phenobarbital, rifampin, other CYP3A4 inducers: decreased modafinil blood level

Cyclosporine, theophylline: decreased blood levels of these drugs

Diazepam, phenytoin, propranolol, tricyclic antidepressants, warfarin: increased blood levels of these drugs

Hormonal contraceptives: decreased contraceptive efficacy

Itraconazole, ketoconazole, other CYP3A4 inhibitors: increased modafinil blood level

Methylphenidate: delayed modafinil absorption

Drug-diagnostic tests. Aspartate aminotransferase, eosinophils, gamma-glutamyl transferase, glucose: increased levels

Hepatic enzymes: abnormal levels

Patient monitoring

• Monitor respiratory and cardiovascular status, including vital signs and ECG.

• Monitor neurologic status, including mood, motor function, cognition, and emotional lability.

• Monitor blood glucose level in diabetic patient.

• Monitor patient carefully if he is also receiving MAO inhibitors. (However, interaction studies with MAO inhibitors haven't been done.)

Patient teaching

• Tell patient he may take with or without food, but that food may delay drug absorption up to 1 hour.

☞ Advise patient to immediately report chest pain, irregular heart beats, light-headedness, or fainting.

• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, vision, motor function, and alertness.

• Instruct female patient to use reliable nonhormonal contraception during and for 1 month after therapy.

• Tell diabetic patient to monitor blood glucose level closely and stay alert for hyperglycemia.

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