NEW ORLEANSA large review with long-term follow-up of patients from
Group Health Cooperative of Puget Sound, Seattle, seems to put to
rest any fears that short-term use of metronidazole may cause cancer
Several factors have raised concerns about metronidazole: its
mutagenic activity in vitro, its carcinogenic potential in animals,
and its expanded use in humans. Previous studies that have attempted
to assess its potential to cause cancer have been limited in patient
size or duration of follow-up. None has looked at patients so long
after exposure as the new study, which was reported at the 36th
Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).
Dr. Matthew Falagas, of New England Medicine Center and Tufts
University School of Medicine, reported data on patients who received
the drug as outpatients between 1975 and 1983. The 30,000 users
included 21,000 females and 9,000 males (usually, the sexual partners
of women treated for vaginal infections). Patients were compared with
matched controls (nonusers).
The all-site incidence of cancer after the first 7 years of follow-up
was 652 per 100,000 person-years for metronidazole users, compared
with 662 for nonusers. No site was associated with an increased risk
for cancer, and in the first 7 years after use, nonusers actually had
a higher cancer rate, Dr. Falagas reported.