To evaluate the toxicity of zidovudine (ZDV) prophylaxis in human immunodeficiency virus (HIV)-exposed healthcare workers (HCWs) in Italy, a national protocol for postexposure prophylaxis has been implemented and a national registry has been established. All Italian clinical centers licensed to dispense ZDV participate. As of December 1995, data from 674 individuals who received ZDV prophylaxis have been collected. In three cases ZDV was used in combination with either didanosine (DDI) or dideoxycytidine (DDC). In 556 cases (82%), the daily dose of ZDV was 1,000 mg/day; 21 HCWs (3%) were treated with 300-800 mg/day, and in 72 persons (11%) the dose was 1,200- 3,000 mg/day. A total of 332 (49%) HCWs reported at least one adverse effect; 132 (20%) discontinued prophylaxis because of side effects (40% of those reporting side effects). Nausea was reported in 243 cases; other side effects included vomiting, gastric pain, diarrhea, asthenia, and headache. Most constitutional adverse effects were reported during the first week of prophylaxis. Grade 1 anemia (hemoglobin 9.5-11 g/dL) occurred in 10 cases (3%); in 2 cases, the neutrophil count decreased to 3. A transient increase of serum alanine aminotransferase to three times the upper limit of normal was observed in 7 persons. All side effects were reversible after the prophylaxis was stopped. Among those reporting at least one side effect the mean duration of treatment was 22 days; for HCWs reporting hematologic or liver adverse effects the mean length of treatment was 34 days. A total of 351 HCWs (54.6%) ceased the treatment before the scheduled 1-month period. In the 132 persons who discontinued treatment because of side effects, the mean length of prophylaxis was 8 days. One HCW seroconverted after conjunctival exposure to blood. The short-term toxicity of ZDV prophylaxis is frequent, mild, dose related, and reversible. Further studies are needed to assess the risk of long-term sequelae of this treatment as well as of prophylaxis with combinations of antiretroviral drugs.
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