Our article on Antiviral Drugs for Prophylaxis and Treatment of Influenza (Med Lett Drugs Ther 2005;47:93) mentioned possible use of amantadine (Symmetrel, and others) and rimantadine (Flumadine, and others), but warned that the incidence of resistance has increased substantially. The CDC recently issued a Health Alert (www.cdc.gov) saying that current evidence indicates that a high proportion of circulating influenza A viruses in the US are now resistant to amantadine and rimantadine and they should not be used for this indication, at least this year. Click here to go to this update...

The FDA has approved an extended-release (ER) capsule formulation of amantadine (Gocovri – Adamas) for once-daily treatment of levodopa-induced dyskinesia in patients with Parkinson's disease (PD). It is the first product to be approved in the US for this indication. Immediate-release (IR) amantadine has been used off-label for years to manage levodopa-induced dyskinesia.

The FDA has approved an extended-release tablet formulation of amantadine (Osmolex ER – Vertical/Osmotica) for once-daily treatment of Parkinson's disease (PD) and drug-induced extrapyramidal symptoms (EPS) in adults. An extended-release capsule formulation of amantadine (Gocovri) was approved in 2017 for treatment of levodopa-induced dyskinesia in patients with PD.

Rimantadine hydrochloride (Flumadine - Forest), the alpha-methyl derivative of amantadine (Symmetrel, and others), was recently approved by the US Food and Drug Administration for prevention and treatment of influenza A virus infections in adults and for prevention of influenza in children.

The motor symptoms of Parkinson's disease (PD) are caused primarily by degeneration of dopaminergic neurons in the substantia nigra. The nonmotor symptoms of the disease are thought to be caused by degeneration of other neurotransmitter systems. No disease-modifying drugs are available for treatment of PD.

View the Comparison Table: Drugs for Parkinson's Disease

Zanamivir, a neuraminidase inhibitor taken by inhalation, has been approved by the FDA for treatment of influenza. Oseltamivir phosphate, an oral neuraminidase inhibitor, will probably be approved soon.

Carnitine is a naturally occurring amino acid derivative essential for transport of long-chain fatty acids into mitochondria. It is advertised on the Internet as a dietary supplement that can promote weight loss, increase energy, enhance athletic performance and slow aging. Levocarnitine (Carnitor - Sigma-Tau) has been FDA approved for oral and parenteral treatment of primary carnitine deficiency since 1986. Products containing levocarnitine and its synthetic derivative acetyl-L-carnitine are available as dietary supplements in the US.

Since publication of our recent article on antiviral drugs for influenza, increased levels of resistance to oseltamivir (Tamiflu) have been detected in influenza A H1N1 strains.

Bupropion hydrochloride, currently available as an antidepressant (Wellbutrin - Medical Letter, 31:97, 1989; Wellbutrin SR), is now being marketed in a sustainedrelease formulation as Zyban (Glaxo Wellcome) for use as an aid in smoking cessation.