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therapeutic drugs

Sunday 29 January 2006

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An adverse drug reaction is defined as a toxic or undesired response to a drug used at therapeutic doses to prevent, diagnose, or treat disease.

It is estimated that approximately 2 million hospitalized patients suffered from serious adverse drug reactions in 1994, resulting in 106,000 deaths. These estimates are conservative because they do not include errors in drug dosage or administration or patient noncompliance.

Predictable reactions are based on the known toxicity or mechanism of action of a drug; these reactions are usually related to dose. Individual variations or polymorphisms in drug-metabolizing enzymes contribute to variable responses to drug therapy and an increased incidence of side effects.

At least 5% of commonly prescribed drugs are metabolized by the cytochrome P-450 CYP1A2 pathway; approximately 12% of Caucasians carry variant alleles that reduce drug metabolism by this pathway.

Pharmacogenomics is a new field that uses genotyping to predict and prevent adverse drug reactions; for example, children with leukemia are screened for thiopurine methyltransferase variants to determine the optimal dose of azathiopurine, and genotyping for the cytochrome P-450 CYP2D6 enzyme will help individualize doses of antipsychotic drugs to reduce side effects.

In contrast to these predictable types of adverse drug reactions, idiopathic or idiosyncratic reactions are rare and unpredictable, although the consequences may be severe or even fatal.

Herbal medicines are widely used in the United States and throughout the world; although many of these preparations have been shown to be effective in short-term trials, there is lack of quality control in this industry and few long-term studies of effectiveness and safety.

The most commonly used herbal medicines in the United States can produce adverse effects, including allergic or hypersensitivity reactions, and potentially serious interactions with prescription drugs.