Not all contraceptive products contraindicated in women taking certain hepatitis C treatments carry warnings about the increased risk of adverse events when the two drugs are taken together, the TGA has warned.

Alanine aminotransferase levels (ALT) more than five times the normal range have been reported in female patients taking Viekira PAK and Viekira PAK-RBV who were also on ethinylestradiol-containing medications, the drug regulator said in a medicines safety update issued earlier this week.

The  contraindicated medicine is found in almost all formulations of combined birth control pills, as well as in contraceptive patches, and contraceptive vaginal rings.

While the manufacturer of the hepatitis treatment does advise patients to stop taking ethinyl estradiol-containing medications manufacturers of the drugs that contain the ethinylestradiol have not been so quick to update the warning labels on their products.

The TGA reports that during clinical trials elevated ALT levels observed in patients who were taking ethinyl estradiol-containing medications typically occurred during the first four weeks of treatment and declined usually within around two weeks.

It added that this issue also affects a new drug, Technivie, which is not yet marketed in Australia but has been recently registered as a treatment for genotype 4 chronic HCV in combination with ribavirin.