Rimantadine

Rimantadine (INN, sold under the trade name Flumadine) is an orally administered antiviral drug used to treat, and in rare cases prevent, influenzavirus A infection. When taken within one to two days of developing symptoms, rimantadine can shorten the duration and moderate the severity of influenza. Both rimantadine and the similar drug amantadine are derivates of adamantane. Rimantadine was approved by the Food and Drug Administration (FDA) in 1994.

According to the CDC, 100% of seasonal H3N2 and 2009 pandemic flu samples tested have shown resistance to rimantadine and it is no longer recommended to prescribe for treatment of the flu.

History
Rimantadine was discovered in 1963 and patented in 1965 in the USA by William W. Prichard in Du Pont & Co., Wilmington, Delaware (US patent on new chemical compound № 3352912, 1965 and on the first method of synthesis № 3592934, 1967). Prichard's methods of synthesis of rimantadine from the corresponding ketone oxime were based on its reduction with lithium aluminum hydride.

Clinical usage
Rimantadine is believed to inhibit influenza's viral replication, possibly by preventing the uncoating of the virus's protective shells, which are the envelope and capsid. Genetic studies suggest that the virus M2 protein, an ion channel specified by virion M2 gene, plays an important role in the susceptibility of influenza A virus to inhibition by rimantadine. Resistance to rimantadine can occur as a result of an amino acid substitutions at certain locations in the transmembrane region of M2. This prevents binding of the antiviral to the channel.

Rimantadine, like its antiviral cousin amantadine, possesses some NMDA antagonistic properties and is used as an antiparkinsonic drug (i.e., in the treatment of Parkinson's disease). However, neither rimantadine nor amantadine are preferred agents for this therapy and are generally reserved for cases of the disease which are less responsive to front-line treatments.

Drug interactions
Taking paracetamol (acetaminophen e.g. Tylenol) or acetylsalicylic acid (aspirin) while taking rimantadine is known to reduce the body's uptake of rimantadine by approximately 12%. Cimetidine also affects the body's uptake of rimantadine.

Possible side effects
Rimantadine can produce gastrointestinal and central nervous system adverse effects. Approximately 6% of patients (compared to 4% of patients taking a placebo) reported side effects at a dosage of 200 mg/d. Common side effects include:


 * nausea
 * upset stomach
 * nervousness
 * tiredness
 * lightheadedness
 * trouble sleeping
 * difficulty concentrating