A comparison of Norinyl and Brevicon in three sites in Sri Lanka

Abstract

A set of 3 four-cell randomized, blind clinical trials was carried out in Sri Lanka to evaluate the impact of vitamin supplements and different oral contraceptive formulations. This paper concentrates on the comparisons of oral contraceptives. There seems to be no important difference between Norinyl, a standard-dose oral contraceptive, and Brevicon of a lower estrogen dosage--in either continuation or side effects. Continuation at one site was higher among Norinyl users, but several factors led us to the belief that this difference was due to differences in field worker performance rather than to the pharmacological properties of the drugs. Some differences in side effects were observable along predictable lines; breakthrough bleeding was more common among Brevicon users than Norinyl users, and most other side effects were more frequent among Norinyl users, although these latter differences were quite small, and there were several exceptions.

PIP: Between September 1978 and December 1980 a set of 3 4-cell randomized blind clinical trials were carried out in Sri Lanka to evaluate the impact of vitamin supplements and different oral contraceptive (OC) formulations. The 4 treatments of the study were: Norinyl, the standard OC used in Sri Lanka, with a daily multi-vitamin supplement; Norinyl with placebo; Brevicon, a lower dose OC, with a vitamin supplement; and Brevicon with placebo. Focus here is on the 3 2-cell comparisons of Norinyl versus Brevicon. 500 women recruited from low income areas of Colombo were assigned to the 4 treatments at random. 2 other trials were conducted according to a somewhat different design in rural areas of the Districts of Matara in the South and Puttalam in the North. The 4 treatment combinations used in the urban study were assigned on a sequential basis, after a random start, to acceptors on entry into the study. The 1st follow-up visit, conducted in the home by home visitors, was scheduled for 1 month after admission and succeeding visits were scheduled at 2-3 month intervals. In the urban study, recruitment was limited to low income areas with reasonable access to the clinic and to physically healthy women 18-40 years of age with no known or suspected contraindications to OCs and who had terminated their last pregnancy more than 3 months previously. Eligibility requirements for the rural study were the same as the urban study, except that women up to age 49 and those currently breastfeeding were included. The Colombo acceptors were younger than the Matara acceptors, were better educated, had fewer children, wanted fewer additional children, and were more likely to have previously used contraception. There were no striking or consistent differences in continuation. There were gross rates of termination by reason, site, and treatment. Differences by site were far more striking than differences by treatment within site. Of particular note were: the low proportion of dropouts due to menstrual side effects in Colombo; the predominance of "other medical" terminations in the rural areas; and the high urban lost to follow-up rate. Rates of unplanned pregnancy did not differ noticeably by treatment, in any site. Breakthrough bleeding was more common among Brevicon users than Norinyl users, and most other side effects were more frequent among Norinyl users, although these latter differences were quite small and there were several exceptions. In sum, there appears to be no important difference between Norinyl and Brevicon in either continuation or side effects.