Contraceptive efficacy of single and divided doses of chlormadinone acetate

Effectiveness and efficacy rates of progestin-only pills: A comprehensive literature review

OBJECTIVES

To synthesize published literature on POP effectiveness and efficacy.

STUDY DESIGN

We searched PubMed Central, PubMed, and the Cochrane library through March 07, 2022. We included articles written in English reporting a Pearl Index or life table rate for pregnancy. We excluded articles only assessing formulations that: were never marketed globally, are only sold in combination with estrogen, are currently sold only for noncontraceptive purposes, or were not given to participants continuously. Four researchers independently extracted data and two analyzed data using Excel and R.

RESULTS

We included 54 studies. Among studies at low or moderate risk of bias, the median Pearl Index rate (the failure rate during typical use) was 1.63 (range 0.00-14.20, IQR 4.03) and the median method failure Pearl Index rate (the failure rate during perfect use) was 0.97 (range 0.40-6.50, IQR 0.68). Excluding the newer formulations, Desogestrel and Drospirenone, which are closer to combined oral contraceptives in that they prevent pregnancy by inhibiting ovulation, the median Pearl Index rate is 2.00 (range 0.00-14.12, IQR 2.5) and the median method failure Pearl Index rate is 1.05 (range 0.00-10.90, IQR 1.38).

CONCLUSIONS

Among studies at low or moderate risk of bias, the median Pearl Index rate during typical POP use was much lower than currently estimated (7.00), while the median perfect use rate was similar to current estimates.

IMPLICATIONS

Future research should investigate the possibility that POPs may be much more effective during typical use than currently believed.

The metabolic fate of chlormadinone acetate in the baboon

The metabolic fate of chlormadinone acetate (17alpha-acetoxy-6-chloro-4, 6-pregnadiene-3, 20-dione; CAP) was studied in intact and biliary fistula baboons. The steroid was labeled with 3H at position 1 and with 14C at the carboxyl moiety of the 17alpha-acetate, thus affording the opportunity to ascertain the loss of the 17alpha-acetoxy group and the fate of both labels. The averages of the radioactivity excreted, given as percentages of the amounts injected, and the standard deviations were as follows: In the urine of intact animals after 6 hours, 5.7 +/- 0.2% and 5.5 +/- 0.7% of the 3H and 14C were recovered, respectively. After 6 days, there was 17.5% of the 3H and 16.2% of the 14C in the urine plus 15.3% of the 3H and 16.4% of the 14C in the feces. In baboons with biliary fistulas, the total radioactivity excreted was 7.8 +/- 0.7% of the 3H and 11.6% of the 14C in the urine, and 30.9 +/- 4.4% of the 3H and 30.7% of the 14C in the bile after 6 hours. Glucosiduronates were the predominant conjugates in the urine and bile. The similarity in the urinary excretion of radioactivity in the first 6 hours in intact and biliary fistula animals, the relatively low excretion of radioactivity in the bile and after 6 days in the urine, and the low fecal excretion suggest that the metabolites of CAP are not involved in an extensive enterohepatic circulation in the baboon. Deacetylation of the 17alpha-acetate in CAP was detected in the early collection periods of the urine and bile and constituted a very small percentage of the injected compound. No significant oxygenation of CAP at position 1 was detected. The metabolism of CAP is discussed and compared to our previously reported data on the metabolism of progesterone, ethynodiol diacetate and medroxyprogesterone acetate and the data on other progestogens reported in the literature. It appears that the excretion of CAP is significantly slower in the baboon than that of the other progestogens. The amounts of glucosiduronates of CAP and/or its metabolites formed in vivo are less than those formed with the other progestogens. Also, the extent of deacetylation of the 17alpha-acetate of CAP is much less than that of the 3beta-acetate of ethynodiol diacetate.