Amantadine
Mechanism :
While the mechanism of action of amantadine in the treatment of Parkinson’s syndrome and drug-induced extrapyramidal reactions is not known, it is believed to release brain dopamine from nerve endings making it more available to activate dopaminergic receptors. The drug does not possess anticholinergic activity in animal tests at doses similar to those used clinically.
The antiviral activity of amantadine for the prophylaxis of Asian (A 2) influenza in humans appears not to be related to the possible mode of action of this drug in Parkinson’s syndrome. As an antiviral, it blocks the uncoating of influenza A virus preventing penetration of virus into host and inhibits M2 protein in the assembly of progeny virions.
Indication :
- Treatment and prophylaxis of influenza A infection.
Contraindications :
Known hypersensitivity to amantadine. Patients with a history of epilepsy or other seizures should be observed closely for possible increased seizure activity. A small number of suicidal attempts, some of which have been fatal, have been reported in patients treated with amantadine. Patients with a history of CHF or peripheral edema should be followed closely as there are patients who developed congestive heart failure while receiving amantadine.
Dosing :
1-9 years: 5 mg/kg/day divided doses every 12 hours for 3-5 days; Maximum dose: 150 mg/day.
9-12 years: 100 mg orally every 12 hours for 3-5 days.
Adverse Effect :
Nausea, dizziness, insomnia, depression, anxiety, irritability, hallucinations, confusion, anorexia, dry mouth, constipation, ataxia, livedo reticularis, peripheral edema, orthostatic hypotension, headache, somnolence, nervousness, dream abnormality, dry nose, diarrhea and fatigue. Rare side effects: urinary retention, dyspnea, skin rash, hypertension, corneal opacity, corneal edema, decreased visual acuity, convulsion, leukopenia, neutropenia, oculogyric episodes, suicidal ideation.
Interaction :
The dose of anticholinergic drugs or of amantadine should be reduced if atropine-like effects appear when these drugs are used concurrently.
Metoclopramide: May diminish the therapeutic effect of Anti-Parkinson's Agents
Influenza Virus Vaccine (Live/Attenuated): Antiviral Agents (Influenza A and B) may diminish the therapeutic effect of Influenza Virus Vaccine.
CNS stimulants: Careful observation is required when amantadine is administered concurrently with CNS stimulants.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 35–50 | 100 mg every 24 hours |
| 15–35 | 100 mg every 48–72 hours |
| <15 | 100 mg every 7 days |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Not dialysed. Dose as in GFR<10 mL/min |
| HD | Not dialysed. Dose as in GFR<10 mL/min |
| HDF/High flux | Unknown dialysability. Dose as in GFR<15 mL/min |
| CAV/VVHD | Unknown dialysability. Dose as in GFR=15–35 mL/min |
Hepatic Dose :
No dosage adjustments are recommended.