Objective: To evaluate serum levels of liver enzymes and bilirubin before and after six cycles of use of a triphasic oral contraceptive containing 35 mg of ethinylestradiol and 180/215/250 mg of norgestimate (Pramino ® , Janssen-Cilag). Design: A prospective, open-label, non-comparative, multicentric phase IV study. Setting: Department of Obstetrics and Gynaecology, 1 st Medical Faculty, Charles University, Pra- gue. Method: Before the start and after six cycles of Pramino use, the levels of alanine aminotransfera- se (ALT), aspartate aminotransferase (AST), g-glutamyltransferase (GMT), and bilirubin were de- termined in women. As the analyses were performed in different laboratories, the evaluation involved: 1. Subgroups of women examined in laboratories with the same reference range; 2. A group of women examined in laboratories with the upper reference range within the mean ± SD interval; 3. Percentage variations of the measured values from a concrete upper reference limit. Results: When evaluating subgroups of women from laboratories with the same standards, signifi- cant decreases in AST and bilirubin were seen in some subgroups, a rise in GMT in one subgroup; the other changes were non-significant. When assessing the entire group and percentage variati- ons from standard, a mild rise in GMT was again seen; however, the values remain deep within the normal range. Values above the upper reference limit at the start of the study either do not change significantly throughout the study, or they normalize spontaneously. Conclusion: No clinically significant changes in liver function tests occurred in users of a tripha- sic oral contraceptive containing norgestimate along with 35 mg EE over a period of six cycles of use. The results, as judged by their dynamics, suggest liver function tests are not a useful tool for routine monitoring a healthy combined oral contraceptive user.

        Key words: hormonal contraception, liver function tests, alanine aminotransferase, aspartate ami- notransferase, g-glutamyltransferase