Lipid and lipoprotein changes during the seven days off oral contraception in women using two triphasic preparations

This study was designed to determine whether mean values for lipids and lipoproteins changed during the 21 days on oral contraceptive (OC) preparations and during the seven days off the pills. The design allowed for comparison of the effects of Triphasil and Ortho 777 and for examining the consistency over two pill cycles. The mean values for total cholesterol, HDL-cholesterol, LDL-cholesterol and HDL3-subfraction were consistently lower on Day 20 when compared to Day 2 (p less than 0.05) for the two cycles and higher on Day 2 of Cycle II when compared to Day 20 of Cycle I. This fall-rise-fall pattern was consistent for cholesterol in 17 out of 28 of the women studied and these women were heavier (p less than 0.05), had a greater mean Quetelet Index (p less than 0.05) and had been using OCs for a shorter mean period of time (p less than 0.05). Consistently higher apolipoprotein A1 mean values were found on Day 20 of both cycles for Triphasil users compared to Ortho 777 users (p less than 0.02). This paper discusses the importance of these findings in relation to study design when measuring for differences between OC preparations and changes over time.