Changes caused by one drug in the absorption, distribution, metabolism or excretion of another may lead to a pharmacokinetic adverse drug interaction (DN Juurlink et al, JAMA 2003; 289:1652). Additive drug interactions, such as vasodilation caused by both sildenafil (Viagra) and nitrates, can also have adverse effects.

The ability of grapefruit juice to increase serum concentrations of drugs was first discovered during a study of the effect of ethanol on felodipine (Plendil) pharmacokinetics. Double-strength grapefruit juice used to disguise the taste of ethanol resulted in higher than expected serum concentrations of felodipine (DG Bailey et al, Clin Invest Med 1989; 12:357).

Duloxetine hydrochloride (Cymbalta - Lilly), a selective serotonin and norepinephrine reuptake inhibitor (SNRI), has been approved by the FDA for treatment of major depressive disorder in adults, and more recently for diabetic peripheral neuropathy as well. The Medical Letter will review its role in diabetic neuropathy in a future issue.

The FDA has approved the marketing of desvenlafaxine (Pristiq - Wyeth), the main active metabolite of venlafaxine (Effexor, and others - Wyeth), for treatment of major depressive disorder. Venlafaxine, a norepinephrine and serotonin reuptake inhibitor (SNRI), is available generically as an immediate-release tablet. Venlafaxine extended-release capsules (Effexor XR) are scheduled to go off-patent in 2010.

Depression occurs in up to 20% of pregnant women, and the use of selective serotonin reuptake inhibitors (SSRIs) in these women has been increasing. Maternal depression has itself been associated with intrauterine growth problems and low birth weight, so the risks of exposure to antidepressants during pregnancy must be weighed against the risks of untreated depression, which also include self-harm, poor bonding and poor parenting. SSRIs available in the US for treatment of depression include citalopram (Celexa, and others), escitalopram (Lexapro), fluoxetine (Prozac, and others), paroxetine...

Atovaquone (Mepron - Burroughs Wellcome), a hydroxynaphthoquinone, was recently approved by the US Food and Drug Administration (FDA) for oral treatment of mild to moderate Pneumocystis carinii pneumonia (PCP) in patients who cannot tolerate trimethoprim-sulfamethoxazole (Septra, Bactrim, and others). PCP is a common opportunistic infection and frequent cause of death in patients with AIDS.

Five different selective serotonin reuptake inhibitors (SSRIs) are promoted for treatment of depression and a sixth (fluvoxamine) for use in obsessive compulsive disorder. Which one should we prescribe for our patients?

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.

A selective serotonin reuptake inhibitor (SSRI) is generally used for initial treatment of major depressive disorder (MDD). A serotonin-norepinephrine reuptake inhibitor (SNRI), bupropion (Wellbutrin SR, and others), and mirtazapine (Remeron, and others) are reasonable alternatives. Improvement in symptoms can occur within the first two weeks of treatment with these drugs, but a substantial benefit may not be achieved for 4-8 weeks.

Alzheimer's disease (AD) is the most common cause of dementia, but cognitive decline is also associated with other neurological conditions such as Parkinson's disease, dementia with Lewy bodies, vascular dementia, and frontotemporal dementia.