Toivonen J, Lähteenmäki P, Luukkainen T
Contraception. 1979 Apr;19(4):401-9. doi: 10.1016/0010-7824(79)90034-9.
Contraceptive vaginal rings (CVR) releasing levonorgestrel and estradiol were used for contraceptive purposes in eight women. They were instructed to remove the CVR for five days only, in the case of bleeding. Three selected subjects were followed by plasma sampling during the first 60 days of treatment. Plasma concentrations of levonorgestrel, progesterone, estradiol and gonadotropins were determined. All subjects kept bleeding records and were controlled clinically in the course of treatment. The subjects were protected an average of 163 days by the CVR. Three subjects used the CVR 170--180 days without removing it and two subjects had to remove the CVR only once. Two subjects experienced quite regular bleedings, and metrorrhagic bleeding was present in one case. No pregnancies were observed during the follow-up period of 1304 days. Clinical examination revealed no pathological findings. The vaginal mucosa tolerated the treatment well. Out of those subjects who were followed by plasma sampling, pituitary suppression was more marked in the subject with continuous use of CVR.
含左炔诺孕酮和雌二醇的避孕阴道环（CVR）被用于8名女性的避孕。她们被指示在出血情况下仅取出CVR 5天。在治疗的前60天，对3名选定的受试者进行了血浆采样。测定了左炔诺孕酮、孕酮、雌二醇和促性腺激素的血浆浓度。所有受试者都记录了出血情况，并在治疗过程中接受临床检查。受试者使用CVR平均避孕163天。3名受试者使用CVR 170 - 180天未取出，2名受试者仅取出CVR一次。2名受试者出现相当规律的出血，1例出现子宫出血。在1304天的随访期内未观察到妊娠。临床检查未发现病理结果。阴道黏膜对治疗耐受性良好。在接受血浆采样的受试者中，持续使用CVR的受试者垂体抑制更为明显。
