Mantadin100 mg

Mantadin is indicated for the following conditions, with evidence strength noted for each:

Established / FDA-approved uses

• Parkinson's disease: Idiopathic Parkinson's disease, postencephalitic parkinsonism, and parkinsonism associated with carbon monoxide intoxication. Mantadin is used as monotherapy in early or mild disease, or as an adjunct to other antiparkinsonian agents such as levodopa.
• Drug-induced extrapyramidal reactions: Mantadin is used to treat extrapyramidal symptoms (e.g., rigidity, tremor, dystonia) caused by antipsychotic (neuroleptic) medications.
• Influenza A prophylaxis and treatment: Mantadin was historically approved for prophylaxis and treatment of uncomplicated influenza A respiratory illness. This use is now considered largely obsolete because circulating influenza A strains have developed widespread resistance to adamantanes; health authorities (including the CDC) generally no longer recommend Mantadin for influenza unless susceptibility of the circulating strain is confirmed.

Notes on evidence strength

The Parkinson's disease and drug-induced extrapyramidal reaction indications are well established. The influenza indication, while still present on some regulatory labels, should only be used based on current local resistance-surveillance data and physician judgment, not as first-line antiviral therapy.

Each tablet/capsule contains Amantadine Hydrochloride as the active ingredient, commonly available in strengths such as 100 mg. Oral syrup formulations may contain Amantadine Hydrochloride equivalent to 50 mg amantadine base per 5 mL. Strength and formulation (tablet, capsule, or syrup) vary by manufacturer; refer to the specific product label for exact composition.

Mantadin is a synthetic tricyclic amine (adamantane derivative) with dual antiviral and antiparkinsonian (dopaminergic) activity. It was originally developed as an antiviral agent against influenza A and was later found, largely by clinical observation, to improve symptoms of Parkinson's disease.

Mantadin is administered orally as tablets, capsules, or oral solution/syrup. It is well absorbed from the gastrointestinal tract, is not significantly metabolized, and is eliminated largely unchanged by the kidneys, which makes renal function an important consideration in dosing.

Mantadin belongs to the adamantane class of antiviral agents and is also classified as an antiparkinsonian (dopaminergic/anti-dyskinetic) agent.

The precise mechanism of Amantadine Hydrochloride is not completely understood, but it is believed to act through several pathways:

• Antiparkinsonian action: Amantadine Hydrochloride is thought to increase the release of dopamine from presynaptic neurons, block dopamine reuptake, and act as a weak antagonist of NMDA-type glutamate receptors, contributing to improvement in rigidity, tremor, and bradykinesia.
• Antiviral action: Amantadine Hydrochloride blocks the M2 proton ion channel of the influenza A virus, interfering with viral uncoating and preventing the release of viral nucleic acid into the host cell, thereby inhibiting viral replication. This mechanism is ineffective against influenza B and against influenza A strains that have acquired M2 channel mutations (widespread in currently circulating strains).

Amantadine Hydrochloride is rapidly absorbed after oral administration, undergoes minimal hepatic metabolism, and is excreted largely unchanged in the urine via glomerular filtration and tubular secretion, with an elimination half-life of approximately 10-30 hours in patients with normal renal function (prolonged in renal impairment).

Mantadin may be taken with or without food; taking it with food may reduce stomach upset. Tablets/capsules should be swallowed whole with water; the oral solution should be measured with an accurate dosing device. If taken once daily, morning administration is preferred to reduce the risk of insomnia. Do not stop Mantadin suddenly in Parkinson's disease without consulting a physician, as abrupt discontinuation can cause serious withdrawal effects (see Precautions and Warnings).

Mantadin has the following clinically significant drug interactions:

• CNS stimulants: Concomitant use with other central nervous system stimulant drugs may lead to additive CNS excitatory effects (nervousness, insomnia); such combinations require careful monitoring.
• Anticholinergic drugs: Co-administration with anticholinergic agents may potentiate anticholinergic side effects (confusion, hallucinations, dry mouth); if these occur, the dose of the anticholinergic agent should be reduced first.
• Thioridazine: Concurrent use has been reported to worsen tremor in some elderly patients with Parkinson's disease.
• Triamterene/hydrochlorothiazide: This combination has been shown to reduce renal clearance of Mantadin, increasing plasma concentrations and the risk of toxicity.
• Quinine and quinidine: These drugs reduce the renal clearance of Mantadin by roughly 30%, which may necessitate dose adjustment.
• Live attenuated influenza vaccine (LAIV): Mantadin should not be given within 2 weeks before or 48 hours after LAIV administration, as it may interfere with vaccine efficacy; inactivated influenza vaccines do not have this restriction.

Side effects of Mantadin are generally dose-related and more common in elderly patients or those with renal impairment.

Common (5-10%)

• Nausea
• Dizziness / lightheadedness
• Insomnia

Less common (1-5%)

• Dry mouth
• Constipation
• Depression, anxiety, irritability
• Hallucinations, confusion
• Livedo reticularis (a mottled, lace-like purplish-blue skin discoloration, usually on the legs, which is generally reversible after stopping Mantadin)
• Peripheral edema
• Orthostatic hypotension (dizziness on standing)

Rare but serious

• Seizures
• Neuroleptic-malignant-syndrome-like reaction on dose reduction or abrupt withdrawal (see Precautions and Warnings)
• Suicidal ideation or behavior
• Corneal edema with blurred or worsening vision
• Congestive heart failure, psychosis, urinary retention, leukopenia (uncommon)

Patients should seek prompt medical attention for sudden vision changes, high fever with muscle rigidity, or thoughts of self-harm while taking Mantadin.

Pregnancy: Animal studies with Mantadin have shown teratogenic and embryotoxic effects at high doses; there are no adequate and well-controlled studies in pregnant women. Mantadin should be used during pregnancy only if clearly needed and if the potential benefit justifies the potential risk to the fetus. A physician should be consulted before use in pregnancy.

Lactation: Mantadin is excreted into human breast milk. Because of the potential for serious adverse reactions in nursing infants, use of Mantadin is generally not recommended in breastfeeding mothers; a physician should be consulted to weigh alternatives.

The following precautions apply to the use of Mantadin:

• Abrupt discontinuation: In patients with Parkinson's disease, sudden discontinuation or rapid dose reduction of Mantadin can precipitate a neuroleptic-malignant-syndrome-like reaction, with hyperthermia, muscle rigidity, altered consciousness, and elevated muscle enzymes. Mantadin should always be tapered gradually under medical supervision rather than stopped abruptly.
• Psychiatric effects and suicide risk: Mantadin can cause or worsen hallucinations, confusion, agitation, depression, and, rarely, suicidal ideation or behavior, with or without a prior psychiatric history; patients and caregivers should watch for mood or behavior changes, particularly in elderly patients.
• Seizure disorders: Mantadin may lower the seizure threshold; patients with a history of epilepsy or other seizure disorders should be observed closely for increased seizure activity.
• Congestive heart failure and fluid retention: Mantadin can cause or worsen peripheral edema and, less commonly, congestive heart failure; patients with a cardiac history should be monitored closely.
• Orthostatic hypotension: Mantadin may cause a drop in blood pressure on standing; caution is advised, especially in elderly patients or those on antihypertensive drugs.
• Corneal edema and visual disturbances: Sudden blurred vision or progressive vision loss while on Mantadin requires prompt ophthalmologic evaluation, as corneal edema can become permanent if the drug is continued.
• Renal impairment: Because Mantadin is cleared almost entirely by the kidneys, dose adjustment is required in renal impairment to avoid drug accumulation and toxicity (see Dosage and Administration).
• Driving/operating machinery: Mantadin may cause dizziness, blurred vision, or confusion; patients should exercise caution with activities requiring alertness.

Overdose of Mantadin is a medical emergency. Reported manifestations of acute overdose include cardiac arrhythmias, tachycardia, hypertension, pulmonary edema, respiratory distress, renal dysfunction, and central nervous system effects such as severe confusion, agitation, hallucinations, seizures, and coma. Fatalities have been reported at doses as low as 1 gram in some individuals.

If overdose of Mantadin is suspected, seek immediate medical attention or contact a poison control center / emergency services without delay. There is no specific antidote; management is supportive, and may include gastric decontamination if presenting early, intravenous fluids, cardiac monitoring, and other measures as directed by treating physicians in a hospital setting. Do not attempt to manage a suspected Mantadin overdose at home.

Store at room temperature (below 30°C), away from light and moisture. Keep out of reach of children.

Elderly: Elderly patients are more susceptible to the CNS side effects of Mantadin (confusion, hallucinations, dizziness) and may require lower doses (e.g., 100 mg once daily for influenza) and closer monitoring, particularly given age-related decline in renal function.

Renal impairment: Dose reduction is required, as Mantadin is renally eliminated and can accumulate to toxic levels in patients with reduced creatinine clearance (see Dosage and Administration for the adjustment table).

Hepatic impairment: Specific dose adjustment data are limited; Mantadin should be used with caution and clinical monitoring in patients with significant hepatic impairment.

Pediatric use: See Pediatric Uses section.

For Parkinson's disease and drug-induced extrapyramidal reactions, Mantadin is typically used long-term as directed by a physician; some patients experience a reduction in benefit after several weeks to months (tachyphylaxis), which may be managed by temporary dose escalation or a brief drug holiday under medical supervision. For influenza A, when used, treatment is typically limited to a short course of about 3-5 days, or until 24-48 hours after symptoms resolve. Duration should always be individualized by the prescribing physician.

Amantadine Hydrochloride is classified under adamantane antivirals and antiparkinsonian (dopaminergic) agents.

Amantadine Hydrochloride exerts its antiparkinsonian effect primarily by enhancing dopaminergic neurotransmission (increasing dopamine release and blocking reuptake) and by antagonizing NMDA-type glutamate receptors, which helps reduce rigidity and tremor. Its antiviral effect against influenza A results from blockade of the viral M2 ion channel, which prevents viral uncoating inside host cells; this antiviral mechanism is largely ineffective against currently circulating resistant influenza A strains.

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The safety and efficacy of Mantadin for Parkinson's disease and drug-induced extrapyramidal reactions have not been established in children, as these conditions are rare in the pediatric population.

For influenza A prophylaxis/treatment (where locally appropriate based on resistance patterns), Mantadin has established pediatric dosing:

• Age under 1 year: Safety and efficacy not established; not recommended.
• Age 1-9 years: Weight-based dosing of approximately 4.4-8.8 mg/kg/day (commonly cited as 2-4 mg/lb/day), not to exceed 150 mg/day, given in one or two divided doses.
• Age 9-12 years: 100 mg twice daily (200 mg/day).

Pediatric dosing of Mantadin should always be determined and supervised by a physician, with attention to renal function and close monitoring for CNS side effects.