Modafinil 200 mg Tablet (CAS 68693-11-8).

1. Description: Clinical summary.

Modafinil 200 mg (active compound: modafinil) is a wakefulness-promoting agent used to reduce excessive daytime sleepiness. Approved therapeutic indications include:

• Narcolepsy (to reduce excessive daytime sleepiness)
• Shift work sleep disorder (to improve wakefulness during scheduled work hours)
• Excessive sleepiness associated with obstructive sleep apnea/hypopnea syndrome (OSAHS) when residual sleepiness persists despite adequate treatment of the underlying sleep-disordered breathing

Modafinil is a prescription medication and is controlled in some jurisdictions because of potential for misuse. It is typically administered orally as a single daily dose; tablets commonly contain 100 mg or 200 mg. Clinical benefits include improved wakefulness, reduced sleep attacks in narcolepsy, and better alertness during night or rotating shifts. It should be used under medical supervision because of potential adverse effects, drug interactions, and the need to evaluate underlying causes of sleepiness.

2. How does Modafinil 200mg work?: Mechanism of action.

The precise mechanism of action is not fully established. Modafinil produces wakefulness through several central nervous system effects:

• Dopaminergic activity: modafinil inhibits dopamine reuptake by blocking the dopamine transporter (DAT), increasing extracellular dopamine in brain regions that regulate arousal.
• Effects on other neurotransmitter systems: modafinil has been shown to influence orexin (hypocretin), histamine, norepinephrine, serotonin, glutamate, and GABA pathways—actions that together promote cortical activation and wakefulness.
• Overall pharmacological profile differs from classic amphetamine stimulants: it has weaker sympathomimetic effects and lower abuse potential, but can still affect cardiovascular and psychiatric systems.

Pharmacokinetics (typical adult): oral bioavailability is high; peak plasma concentrations occur ~2–4 hours after dosing; elimination half-life is approximately 12–15 hours in healthy adults. Metabolism occurs mainly in the liver, with renal excretion of metabolites.

3. Dosage: Medical and varying usage guidelines.

General principles: dosing should be individualized by indication, patient response, tolerance, comorbidities, and concomitant medications. The following are commonly used regimens for adults (typical recommended ranges). Always follow a prescriber's directions.

• Narcolepsy and excessive sleepiness associated with OSAHS:

  • Typical: 200 mg once daily in the morning.
  • Some patients may be started at lower doses and titrated; total daily doses up to 400 mg have been used in clinical practice, but benefit beyond 200 mg is variable and adverse effects increase with higher doses.

• Shift work sleep disorder:

  • Typical: 200 mg taken approximately 1 hour before the start of the work shift.
  • Do not take prior to intended sleep period; timing is important to avoid insomnia.

• Pediatric use:

  • Use in children and adolescents should be guided by a sleep specialist or pediatrician; regulatory status and dosing recommendations vary by country and indication. Caution is required because of increased risk of serious cutaneous reactions (see Side effects). Do not self-prescribe for children.

• Hepatic impairment:

  • Severe hepatic impairment: reduce dose (for example, half the usual dose—commonly 100 mg/day—but follow specialist guidance and product labeling).
  • Mild-to-moderate hepatic impairment: use with caution and monitor.

• Renal impairment:

  • Because metabolites are renally excreted, dose adjustments may be necessary in severe renal impairment; follow specialist advice.

• Elderly:

  • May have increased exposure and sensitivity; consider starting at lower doses.

Administration tips:

• Take in the morning for daytime sleepiness to reduce the risk of insomnia.
• Avoid taking late in the day.
• If a dose is missed, take it as soon as remembered only if it will not interfere with sleep; otherwise skip it—do not double doses.
• Do not exceed recommended daily dose without medical supervision.

Special precautions:

• Modafinil can reduce effectiveness of combined hormonal contraceptives; use alternative or additional contraceptive methods during treatment and for one month after stopping modafinil unless otherwise advised by a clinician.
• Review all medications for interactions (see Side effects and Interactions).

4. Side effects: Common and rare bad effects.

Common (more frequent) adverse effects:

• Headache
• Nervousness, anxiety, agitation
• Insomnia or sleep difficulty (especially if taken late)
• Nausea, decreased appetite
• Dry mouth
• Dizziness
• Diarrhea or gastrointestinal upset
• Back pain

Less common but important/serious adverse effects:

• Psychiatric reactions: anxiety, irritability, mood changes, mania, hallucinations, psychosis; suicidal ideation has been reported in rare cases. Use with caution in patients with a history of psychiatric disorders and monitor mental status.
• Serious dermatologic reactions: rare but potentially life‑threatening cutaneous adverse events such as Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug rash with eosinophilia and systemic symptoms (DRESS). Any new rash should prompt immediate discontinuation and urgent medical evaluation.
• Hypersensitivity reactions/allergic reactions: angioedema, anaphylaxis (rare).
• Cardiovascular: modest increases in blood pressure and heart rate; rare serious cardiac events reported. Monitor blood pressure and heart rate, especially in patients with underlying cardiovascular disease.
• Hepatic injury: rare cases of elevated liver enzymes and hepatic dysfunction; evaluate if symptoms of liver injury occur (jaundice, dark urine, abdominal pain).
• Dependence and withdrawal: lower abuse potential than classical stimulants but some cases of psychological dependence and withdrawal symptoms have been reported.

Drug interactions and clinical consequences (important to monitor):

• Induction of CYP3A4: modafinil is a moderate inducer and can reduce plasma concentrations of drugs metabolized by CYP3A4 (for example, some hormonal contraceptives, cyclosporine, certain statins), potentially decreasing their effectiveness.
• Inhibition/interaction with CYP2C19: may increase levels of substrates like diazepam and phenytoin initially; complex interactions can occur—monitor concentrations where clinically relevant.
• Reduced efficacy of combined hormonal contraceptives: there is documented risk of contraceptive failure—use alternative/backup contraception while taking modafinil and for one month after discontinuation.
• Interactions with other CNS-active drugs: combining with other stimulants or monoamine oxidase inhibitors (MAOIs) is not recommended; risk of serotonin syndrome is possible when used with serotonergic agents—monitor closely.
• Effects on anticoagulants (warfarin) and antiepileptics (phenytoin, carbamazepine): monitor INR and antiepileptic drug levels and adjust doses as needed.

If an overdose is suspected: signs may include agitation, anxiety, tachycardia, hypertension, drowsiness, confusion, hallucinations, and possibly seizures. Seek emergency medical attention. Management is largely symptomatic and supportive.

Reporting and monitoring:

• Stop modafinil and seek urgent care for signs of severe rash, allergic reaction, new or worsening psychiatric symptoms, chest pain, significant hypertension, or jaundice.
• Routine monitoring may include blood pressure checks, assessment of mood/behavior, and targeted laboratory tests if clinically indicated (liver function tests if hepatic symptoms).

5. Storage: HOW to store it.

• Store at controlled room temperature, typically 20–25°C (68–77°F). Short excursions permitted per product labeling (commonly 15–30°C), but avoid extremes of heat or cold.
• Keep in the original container to protect from moisture and light (follow packaging instructions).
• Store out of reach and sight of children and pets.
• Do not use past the expiration date printed on the package.
• Dispose of unused or expired tablets according to local regulations or take-back programs; do not flush medications down the toilet unless instructed.
• Keep in a secure place if there is concern for misuse or diversion.

General counseling points for patients (summary):

• Take as prescribed—usually 200 mg once daily in the morning for daytime sleepiness; for shift work disorder, take about 1 hour before work.
• Avoid late-day dosing to reduce insomnia.
• Inform your prescriber of all medications, supplements, pregnancy or breastfeeding status, and history of psychiatric or cardiovascular disease.
• Watch for rashes, psychiatric changes, or signs of liver problems and seek immediate medical attention if these occur.
• Use additional contraceptive measures while taking modafinil and for one month after stopping, unless instructed otherwise by your clinician.
• Store safely and return unused medication for proper disposal.

This guide is educational and does not replace individualized medical advice. Prescribers should tailor treatment to each patient and consult product labeling and local regulatory guidance for complete prescribing information.