Symmetrel is commonly prescribed to treat or prevent certain types of the flu virus, treat Parkinson's disease, and treat certain side effects of other medications. This medication works by inhibiting the flu virus from multiplying. Although it is not exactly clear as to how the medicine works for Parkinson's, it is known to affect certain brain chemicals. Common side effects include nausea, dizziness, and insomnia.
Symmetrel® (amantadine hydrochloride) is a prescription medication approved for the following uses:
- Preventing and treating certain types of the flu
- Treating Parkinson's disease and other similar conditions
- Treating certain side effects of other medications, known as "extrapyramidal symptoms" (such as movement disorders caused by antipsychotic medications).
Brand-name Symmetrel is manufactured by Endo Pharmaceuticals, Inc. Generic versions of Symmetrel are made by various manufacturers.
Symmetrel may work for the flu by inhibiting the uncoating of the flu virus, an important step in the replication (the "reproduction") of the virus. Specifically, amantadine (the active ingredient in Symmetrel) inhibits the activity of the influenza virus M2 protein, which forms a channel in the virus membrane. As a result, the virus cannot replicate (make copies of itself) after it enters a human cell.
This medication is effective only for some influenza A viruses and is not effective against influenza B viruses. Because the "bird flu" or "avian flu" virus (H5N1) is a type of influenza A, Symmetrel may work for some strains of this virus. However, many strains of H5N1 influenza are resistant to the drug.
For any given year, the predominant flu strain may or may not be susceptible to Symmetrel. If the predominant flu strain is not susceptible, this medication should not be used to prevent or treat the flu.
It is not known exactly how Symmetrel works for Parkinson's disease and other similar conditions or movement disorders. It is known that the medicine affects several different brain chemicals, including dopamine and NMDA (N-methyl D-aspartate).