Amantadine hydrochloride oral
- Drugs List
- Therapeutic Indications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
Oral formulations containing amantadine
Herpes zoster virus (HZV/VSV) infections (shingles)
Prophylaxis and treatment of influenza A
Treatment of Influenza A
100 mg daily starting as soon as possible after diagnosis and continuing for 4 to 5 days. When amantadine is started within 48 hours of symptoms appearing, the duration of fever and other effects is reduced by one or two days and the inflammatory reaction of the bronchial tree that usually accompanies influenza resolves more quickly.
Prophylaxis of Influenza A
100 mg daily for as long as protection is required, usually up to 6 weeks or for 2 to 3 weeks after influenza vaccination.
100 mg daily for the first week, increasing to 100 mg twice daily. The dose can be titrated against signs and symptoms. Doses exceeding 200 mg daily may provide some additional relief, but may also be associated with increasing toxicity. A dose of 400 mg/day should not be exceeded. Increase dose gradually at one week intervals. Withdrawal should be gradual, e.g. half the dose at weekly intervals. Abrupt discontinuation may exacerbate Parkinsonism, regardless of the patient's response to therapy.
100 mg twice daily for 14 days. Treatment should be started as soon as possible after diagnosis. If post-herpetic pain persists, treatment can be continued for a further 14 days.
Treatment of Influenza A and Prophylaxis of Influenza A
Plasma amantadine concentrations are influenced by renal function. In elderly patients, the elimination half-life is longer and renal clearance of the compound is diminished in comparison to young people. Therefore a daily dose of less than 100 mg, or 100 mg given at intervals of greater than one day, may be appropriate.
(See Dosage; Adult)
Since patients over 65 years of age tend to show lower renal clearance and consequently higher plasma concentrations, the lowest effective dose should be used.
(See Dosage; Adult)
Treatment and prophylaxis of Influenza A
Children aged 10 to 15 years
(See Dosage; Adult)
Patients with Renal Impairment
The total daily dosage of amantadine should be reduced or the dosage interval should be increased in accordance with the creatinine clearance.
Creatinine clearance less than 15 ml/minute - contraindicated by the manufacturer, but the Renal Drug Handbook suggests 100 mg every 7 days
Creatinine clearance 15 to 35 ml/minute - 100 mg every 2 to 3 days
Creatinine clearance greater than 35 ml/minute - 100 mg daily
The above recommendations are for guidance only and physicians should continue to monitor their patients for signs of unwanted effects.
Additional Dosage Information
Amantadine acts within a few days, but may appear to lose efficacy within a few months of continuous treatment. Its effectiveness may be prolonged by withdrawal for 3 to 4 weeks, which seems to restore activity. During this time, existing concomitant antiparkinsonian therapy should be continued, or low dose L-dopa treatment initiated if clinically necessary.
Any antiparkinson drug already in use should be continued during initial amantadine treatment. It may then be possible to reduce the other drug gradually. If increased side effects occur, the dosage should be reduced more quickly. In patients receiving large doses of anticholinergic agents or L-dopa, the initial phase of amantadine treatment should be extended to 15 days.
Children under 10 years
Females attempting to conceive
Within 2 weeks of administration of live influenza virus vaccine
History of gastrointestinal ulceration
History of seizures
Long QT syndrome
Renal impairment - creatinine clearance below 15ml/minute
Torsade de pointes
Precautions and Warnings
Family history of long QT syndrome
Females of childbearing potential
Patients over 65 years
Congestive cardiac failure
Glucose-galactose malabsorption syndrome
Hereditary fructose intolerance
History of cardiovascular disorder
History of torsade de pointes
Uncontrolled narrow angle glaucoma
Correct electrolyte disorders before treatment
Patients at risk of suicide should be closely supervised
Reduce dose in patient with creatinine clearance equal to or below 35ml/min
Advise ability to drive/operate machinery may be affected by side effects
Not all available brands are licensed for all indications
Oral liquid contains hydroxybenzoate: caution in hypersensitivity
Presentations with sorbitol unsuitable in hereditary fructose intolerance
Some formulations contain lactose
Some formulations contain propylene glycol
Consider monitoring ECG in patients at risk of QT prolongation
Monitor serum electrolytes
Avoid abrupt withdrawal
Limit prescribing quantity due to suicide risk
Advise patient to avoid alcohol during treatment
Female: Ensure adequate contraception during treatment
Amantadine should be used with caution in patients with confusional or hallucinatory states or underlying psychiatric disorders, in patients with hepatic or renal impairment, and those suffering from, or who have a history of cardiovascular disorders. Amantadine exacerbates GI and CNS side effects of anticholinergics and L-dopa.
Abrupt discontinuation of amantadine may result in worsening of Parkinsonism. Amantadine should not be stopped abruptly in patients who are treated concurrently with neuroleptics. There have been isolated reports of precipitation or aggravation of neuroleptic malignant syndrome or neuroleptic-induced catatonia following the withdrawal of amantadine in patients taking neuroleptic agents.
Hypothermia has been observed in children, especially in those younger than 5 years of age - use with caution in children for the treatment and prevention of influenza.
Pregnancy and Lactation
Amantadine hydrochloride is contraindicated in pregnancy.
Amantadine-related complications during pregnancy have been reported. Amantadine should not be prescribed in women who wish to become pregnant.
Women of child bearing potential should be advised of the hazards of pregnancy during treatment and adequate contraception should be employed.
The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Amantadine hydrochloride is contraindicated in breastfeeding.
Nursing mothers should not take amantadine, as it passes into breast milk. Undesirable effects have been reported in breast-fed infants.
Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1
Changes in mood
Corneal epithelial oedema
Increases in hepatic enzymes
Neuroleptic malignant syndrome-like effect
Reduced visual acuity
Superficial punctate keratitis
It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.
The following number will direct the caller to the relevant local centre (0844) 892 0111
Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Last Full Review Date: November 2014
Joint Formulary Committee. British National Formulary(online) London: BMJ Group and Pharmaceutical Press Accessed on 24 November, 2014.
Paediatric Formulary Committee. BNF for Children (online) London: BMJ Group, Pharmaceutical Press, and RCPCH Publications Accessed on 24 November, 2014.
The Renal Drug Handbook. 3rd edition. (2009) ed. Ashley, C and Currie, Radcliffe Publishing Ltd, Abingdon.
Summary of Product Characteristics: Amantadine hydrochloride 100mg Capsules/Symmetrel 100mg Capsules . Alliance Pharmaceuticals. Revised August 2014.
Summary of Product Characteristics: Amantadine hydrochloride 50mg/5ml syrup . Alliance Pharmaceuticals. Revised May 2014.
Summary of Product Characteristics: Symmetrel Syrup. Alliance Pharmaceuticals. Revised September 2010.
US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
Available at: https://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT
Amantadine Last revised: 7 September, 2013
Last accessed: 24 November, 2014.
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