A triphasic oral contraceptive pill, CTR-05: clinical efficacy and safety. Ovarian activity suppression by two different low-dose triphasic oral contraceptives.
The primary objective of this study was to compare the safety, contraceptive efficacy, and menstrual cycle patterns in women using triphasic oral contraceptive pills, namely CTR-05, containing 50/100/150 micrograms desogestrel and 35/30/30 micrograms ethinylestradiol, and Orthonovum777 containing 500/750/1000 micrograms norethindrone and 35/35/35 micrograms ethinylestradiol.
                Forty-six female volunteers, satisfying the selection criteria, were evaluated for six cycles, in an open-label, randomized study. Volunteers using CTR-05 were studied for 13 additional cycles for efficacy and safety.
                No serious adverse effects were observed in either group. The incidences of other drug-related adverse effects, such as headache and nausea, were transient in both groups. CTR-05 did not lower levels of high density lipoprotein (HDL) cholesterol. This may be attributed to the lower androgenicity of its progestin component, desogestrel. No pregnancies were reported in either group. Clinical and laboratory parameters remained within normal limits in both groups. In the CTR-05 group, the lower dose of ethinylestradiol did not affect the safety, efficacy and acceptability of the product.
                Desogestrel, with little estrogenic activity and only minimal androgenic activity, leads to lipoprotein changes, resulting in a favorable cardiovascular profile, as well as minimal androgen-related effects, such as hirsutism and acne. In an open, randomized study in an outpatient clinic of a large teaching hospital, thirty-one female volunteers with regular cycles and established ovulation by ultrasonography were given one of two triphasic oral contraceptives containing ethinylestradiol combined with levonorgestrel or desogestrel during six cycles of treatment. The main outcome measures were transvaginal ultrasonography and serum E2 and P measurements in pill cycles 1, 3 and 6. No ovarian activity was found in 10 subjects. Among the remaining 21 women who showed ovarian activity, most follicle-like structures developed in the pill-free week and decreased in size or disappeared in the first pill week. One women taking triphasic desogestrel had evidence of a luteinized unruptured follicle and one women taking triphasic levonorgestrel had a possible ovulation. The latter women also showed symptoms of lower abdominal pain. A statistically significant difference in ovarian activity between the two oral contraceptives could not be established. The two triphasic oral contraceptives suppressed ovarian activity to the same degree. A trend was seen towards increasing ovarian activity with duration of use in both treatment groups.
The available evidence is limited and the internal validity of these trials is questionable. Given the high losses to follow up, these reports may even be considered observational. Given that caveat, the biphasic pill containing norethindrone was associated with inferior cycle control compared with the triphasic pill containing levonorgestrel. The choice of progestin may be more important than the phasic regimen in determining bleeding patterns.