Long-term stability of the anti-influenza A compounds--amantadine and rimantadine.

Amantadine and rimantadine hydrochloride were tested for stability after storage at different temperatures and under different conditions for extended periods of time. Both compounds were quite stable after storage for at least 25 years at ambient temperature; they both retained full antiviral activity after long-term storage or after boiling and holding at 65-85 degrees C for several days. Thus, amantadine and rimantadine could be synthesized in large quantities and stored for at least one generation without loss of activity in preparation for the next influenza A pandemic in humans.