Amantadine and rimantadine for influenza A in adults.

BACKGROUND

Amantadine hydrochloride and rimantadine hydrochloride have antiviral properties, but they are not widely used due to a lack of knowledge of their potential value and concerns about possible adverse effects.

OBJECTIVES

The objective of this review was to assess the efficacy, effectiveness and safety ("effects") of amantadine and rimantadine in healthy adults.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2005), MEDLINE (2003 to August Week 4, 2005), EMBASE (October 2003 to July 2005) and reference lists of articles.

SELECTION CRITERIA

Randomised and quasi-randomised studies comparing amantadine and/or rimantadine with placebo, control medication or no intervention, or comparing doses or schedules of amantadine and/or rimantadine in healthy adults.

DATA COLLECTION AND ANALYSIS

For prophylaxis (prevention) trials the numbers of participants with clinical influenza (influenza-like-illness or ILI) or with confirmed influenza A and adverse effects were analysed. Analysis for treatment trials was of the mean duration of fever, length of hospital stay and adverse effects.

MAIN RESULTS

Amantadine prevented 25% of ILI cases (95% confidence interval (CI) 13% to 36%), and 61% of influenza A cases (95% CI 35% to 76%). Amantadine reduced duration of fever by one day (95% CI 0.7 to 1.2). Rimantadine demonstrated comparable effectiveness, but there were fewer trials and the results for prophylaxis were not statistically significant. Both amantadine and rimantadine induced significant gastrointestinal adverse effects. Adverse effects of the central nervous system and study withdrawals were significantly more common with amantadine than rimantadine. Neither drug affected the rate of viral shedding from the nose and the course of asymptomatic influenza.

AUTHORS' CONCLUSIONS: Amantadine and rimantadine have comparable efficacy and effectiveness in relieving or treating symptoms of influenza A in healthy adults, although rimantadine induces fewer adverse effects than amantadine. The effectiveness of both drugs in interrupting transmission is probably low. Routine use of both drugs should be discouraged and both drugs should only be used when all other measures fail.