AEGiS-CATIE: AZT and Clarithromycin -- drugs not to mix

AZT and Clarithromycin -- drugs not to mix

TreatmentUpdate81 - Vol. 9, No. 7 - pp. 5; September 1997
Sean Hosein

Background and Summary

The antibiotic clarithromycin (Biaxin«) is useful in treating MAC (mycobacterium avium complex) infection as well as the life-threatening brain infection toxo (toxoplasmosis). Researchers in the USA studied the effect of using clarithromycin with AZT. They found that taking the antibiotic with AZT reduced levels of AZT in the blood. To get around this problem they suggest that AZT and clarithromycin be taken at least 2 hours apart.

Study Details

Researchers recruited 15 male HIV-infected volunteers with an average CD4+ cell count of 167 cells. Subjects were placed into one of 4 groups to which doctors assigned different doses of clarithromycin:

* group 1 - 500 mg/12 hours

* group 2 - 1,000 mg/12 hours

* group 3 - 2,000 mg/12 hours

* group 4 - 3,000 mg/12 hours

Readers should note that this study occurred before the NIH warned doctors not to use more than 1 gram/day of clarithromycin when treating PHAs because high doses of the drug were associated with decreased survival compared to lower doses (1 gram/day or less). We will focus on the results from the 1 g/day group. Subjects took clarithromycin for 7 days. On day 1 they also began taking AZT 100 mg every 4 hours (600 mg/day).

Results

The doctors found that when clarithromycin (500 mg/12 hours) and AZT were taken the following happened:

* absorption of AZT was reduced by 12%

* the maximum concentration of AZT in the blood fell by 32%

* the time taken for AZT to reach its highest level in the blood doubled

Results from the other groups suggest that when greater doses of clarithromycin were used, even smaller amounts of AZT were absorbed. According to the researchers, clarithromycin somehow reduces the absorption of AZT. To avoid this problem researchers suggest that PHAs take their AZT "at least 2 hours" apart from their clarithromycin.

REFERENCES:

1. Polis MA, Piscitelli SC, Vogel S, et al. Clarithromycin lowers plasma zidovudine levels in persons with Human Immunodeficiency Virus infection. Antimicrobial Agents and Chemotherapy 1997;41(8):1709-1714.

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