POSSIBLE ASSOCIATION BETWEEN OCULAR CHLORAMPHENICOL AND APLASTIC-ANEMIA - THE ABSOLUTE RISK IS VERY-LOW

Aims To determine whether topical ocular chloramphenicol increases the risk of aplastic anaemia and to estimate the magnitude of this risk, if any. Methods Population-based prospective case-control surveillance of aplastic anaemia in a community of 4.2 million inhabitants from 19 80 to 1995 (67.2 million person-years) plus case-population estimate o f the risk, based on sales figures of ocular chloramphenicol in the st udy area during the study period. Results One hundred and forty-five p atients with aplastic anaemia and 1,226 controls were included in the analysis. Three cases (2.1%) and 5 controls (0.4%) had been exposed to ocular chloramphenicol during the relevant etiological period. The ad justed odds ratio was 3.77 (95% confidence interval, 0.84-16.90). Two cases had also been exposed to other known causes of aplastic anaemia. The incidence of aplastic anaemia among users of ocular chloramphenic ol was 0.36 cases per million weeks of treatment. The incidence among non users was 0.04 cases per million weeks. Conclusions An association between ocular chloramphenicol and aplastic anaemia cannot be exclude d. However, the risk is less than one per million treatment courses.