Modafinils effects on the cytochrome P450 system are of uncertain clinical significance

Inhibition of CYP2C19 and 2 C9 , phenytoin(monitor for features of toxicity)

Warfarin (increase monitoring for the first 2 months of treatment

Induction of CYP3A4/5 , potential for reduced effect of ciclosporin

HIV-protease inhibitors,

Midazolam,calcium -channel blockers, statins and hormonal contraception

Induction of CYPIA2 and 2B6 also occurs

Daytime sleepiness due to nacrolepsy, obstructive sleep apnoea or chronic shift

work related disorder, depression where prognosis (<2-4 weeks) 

fatigue refractory to correction of underlying contributors



















 

Undesirable effects

Very common(>10%)- headache

Common (< 10%, >1%)- abnormal LFTs , tachycardia, paliptation, dizziness,

drowsiness, paraesthesia, blurred vision, abdominal pain, nausea, bowel disturbance,

dry mouth,reduced appitite, vasodilation, chest pain, nervousness, insomnia, anxiety,

depression, confusion

Uncommon (<1%  >1%)- bradycardia, arrhytmia, movement disorders,hostility,

suicidal ideation

Rare (<0.1%) -psychosis, mania, angioedema, serious skin reactions(rare in adults,

but 1% of children, Stevens Johnson syndrome, toxic epidermal necrolysis 

Cautions-

Cardiovascular disease (eg. severe hypertension, arrhythmias, angina.Avoid in mitral

valve prolapse, cor pulmonale and left ventricular hypertrophy), psychiatric illness 

(eg. anxiety agitation, psychosis, addiction disorders, epilepsy (possible lowering of

seizure threshold )

Although rare in adults, serious skin reactions occur in 1% of children, consider

altmoderateernatives where possible (eg.methylphenindate)

Contraindications

Uncontrolled moderate -severe hypertension, arrhythmias

Dose and   usage-

Modafinil is an alternative to methylphenindate particularly where the latter is poorly 

tolerated. The manufacturer recommends a baseline ECG and monitoring of BP 

and heartrate. Dose titration is slower.

start with 100mg each morning after 1 week increase to 200mg each morning

Maximum dose 400mg/24h

The manufacturer recommends either a single morining dose or divided doses in

the morning and at noon. However the half life of modafinil raises the possibility 

of sleep disturbances with the latter

PROVGIL*

CEPHALON

100mg, 200mg  28 days @ 200mg each morning