An extended-release formulation of the centrally-acting muscle relaxant cyclobenzaprine (Amrix - Cephalon) has been approved by the FDA for treatment of muscle spasms. Immediate-release (IR) cyclobenzaprine (Flexeril, and others) has been available since 1977.

The physiologic changes that occur with aging can affect the pharmacokinetics and pharmacodynamics of many prescription and over-the-counter drugs, increasing the likelihood of adverse effects.

Older patients are especially susceptible to drug-induced cognitive impairment. They are more likely to be taking multiple drugs, to have higher blood levels of those drugs because of renal or hepatic dysfunction, and to have pre-existing cognitive problems that make it difficult to detect the role of drugs causing new symptoms or making old ones worse.

Many drugs can cause psychiatric symptoms, but a causal connection is often difficult to establish. Psychiatric symptoms that emerge during drug treatment could also be due to the underlying illness, previously unrecognized psychopathology, or psychosocial factors. The withdrawal of some drugs can cause symptoms such as anxiety, psychosis, delirium, agitation or depression.

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The FDA recently approved the monoamine oxidase inhibitor (MAOI) selegiline in a transdermal (patch) formulation (Emsam - Bristol-Myers Squibb/Somerset) for treatment of major depressive disorder. Selegiline is also available in an oral formulation (Eldepryl, and others) for treatment of Parkinson's disease.

Rasagiline (Azilect - Teva), a monoamine oxidase-type B (MAO-B) inhibitor, was recently approved by the FDA for once-daily oral treatment of Parkinson's disease (PD). It can be taken alone for treatment of early disease or with levodopa/carbidopa (Sinemet, and others) for advanced disease. Selegiline (Eldepryl, and others), the first MAO-B inhibitor marketed in the US, has been available since 1988; a new lower-dose disintegrating tablet (Zelapar) was recently approved.