Pill method failures.

This is a study over a four year period from November 1981 to December 1985 documenting 163 cases of pill method failures in reliable pill takers. In over one third of these cases (36%) there were no predisposing factors. Significant factors which were associated with failure were diarrhoea and/or vomiting in 35%, and breakthrough bleeding on the combined pill in 21%. While there is controversy in the literature about the role of antibiotics in causing pill failure, this study found 23% of failures associated with antibiotic use. Two failures occurred on anticonvulsant medication. Recommendations are made for improved instructions to patients.