Rimantadine is an oral antiviral drug that has been used to treat influenzavirus A, commonly known as the flu. This drug is intended to be taken within a couple of days after flu symptoms first appear. When taken in this way, the drug can shorten the duration and severity of influenza infection. Where available, rimantadine is sold under the brand name Flumadine®.
This medication is a derivative of a chemical compound called adamantane, which in the 1930s was found to be naturally present in petroleum. Other adamantane derivatives such as amantadine and memantine also are antiviral drugs. Some adamantanes have been trialed as anti-human immunodeficiency virus (HIV) drugs.
Rimantadine works by preventing replication of the influenza A virus. It does this by interfering with a key step in replication called uncoating, during which an invading virus sheds its protective shell after it has entered a host cell. Viral genetic information is contained within the protective shell, and if the virus cannot shed its shell, its genetic information cannot be replicated.
In a small proportion of people, this drug can cause minor side effects. These include gastrointestinal effects and central nervous system effects. Side effects that affect the gastrointestinal system can include nausea and upset stomach. Nervous system side effects can include fatigue, nervousness, a lightheaded feeling, difficulty concentrating and insomnia. Serious side effects include yellowing of the skin or eyes, mental confusion, mood changes and skin rash.
This medication also can cause adverse drug reactions when used in conjunction with other medications. Drugs that can react with this antiviral medication include aspirin and paracetamol, also known as acetaminophen. These over-the-counter medications can reduce the effectiveness of the antiviral drug.
In comparison to many other flu drugs, this medication is considered old, having been developed in the 1990s. According to the United States Centers for Disease Control and Prevention, most common flu strains circulating in the population have become resistant to this drug. Resistance is conferred by genetic mutations of a viral protein called M2. When this protein is mutated, the antiviral drug cannot bind to the viral shell to prevent uncoating. As a result of this resistance, most doctors prefer to prescribe newer flu drugs instead of rimantadine.
Although it is no longer used as an influenza drug, this medication does have a use in the treatment of Parkinson’s disease. Rimantadine has what are known as N-methyl d-aspartate (NMDA) antagonistic properties, and it can improve the symptoms of Parkinson’s disease by inhibiting the action of NMDA, a neurochemical. This medication is not considered a frontline treatment but sometimes is prescribed for people who do not respond well to common treatments for Parkinson’s disease.