Guidelines for use of antiretroviral agents continue to shift toward earlier and more continuous treatment, both to treat the patient and to prevent transmission of the disease to others. Resistance testing is now recommended when antiretroviral drugs are started. Increases in HIV RNA levels ("viral load") while on therapy may indicate development of drug resistance, requiring further testing and a change in the treatment regimen. Antiretroviral drugs interact with each other and with many other drugs; complete information on these interactions is available at www.aidsinfo.nih.gov.

Genetic Test for Carbamazepine-Induced Stevens-Johnson Syndrome Carbamazepine (Tegretol, Carbatrol, Equetro, and others), which is now used to treat not only epilepsy but also trigeminal neuralgia and manic episodes in patients with bipolar disorder,1 is a known cause of Stevens-Johnson syndrome (SJS). The incidence of carbamazepine-induced SJS in countries with mainly white populations is 1 to 6 per 10,000 new users of the drug, but Asian patients have a 10-fold higher incidence of this reaction. An association has been found between the human leukocyte antigen (HLA)-B*1502 allele and carbamazepine-induced SJS in a Chinese population.2 This allele occurs almost exclusively in Asians.3,4 The FDA is now recommending that Asian patients be tested for genetic susceptibility to carbamazepine-induced SJS before starting the drug. The genetic test should be available in most clinical chemistry labs.

1. Extended-release carbamazepine (Equetro) for bipolar disorder. Med Lett Drugs Ther 2005; 47:27.
2. WH Chung et al. Medical genetics: a marker for Stevens- Johnson syndrome. Nature 2004; 428:486.
3. C Lonjou et al. A marker for Stevens-Johnson syndrome. . . : ethnicity matters. Pharmacogenomics J 2006; 6:265.
4. A Alfirevic et al. HLA-B locus in Caucasian patients with carbamazepine hypersensitivity. Pharmacogenomics 2006; 7:813.

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Intravenous immunoglobulin (IVIG) has 6 FDA approved indications and is prescribed off-label for many others. How many of these uses are justified is controversial.