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Return of ovulatory cyclicity following an intramuscular injection of medroxyprogesterone acetate (Provera)
RETURN OF OVULATORY CYCLICITY FOLLOWING AN INTRAMUSCULAR INJECTION OF MEDROXYPROGESTERONE ACETATE (PROVES)
Kenneth T. Kirton and James C. Comette Fertility Research, The Upjohn Company Kalamazoo, Michigan
ABSTRACT This study was carried out to determine the relationship between peripheral serum concentrations of medroxyprogesterone acetate (Provera) and progesterone following an intramuscular injection of 150 mg of depomedroxyprogesterone acetate. Medroxyprogesterone acetate concentrations were maximal at 5-20 days post-injection (lo-25 ng/ml), then decreased to 5-10 ng/ml by 30 days post-injection. In general, the concentrations decreased gradually, with little fluctuation, during the remainder of the study (260 days). Medroxyprogesterone acetate concentrations were 5.1, 0.8 and CO.5 ng/ml at the time of the first detected rise in serum progesterone, at 203, 238 and 245 days post-injection. These results indicate that drug was released from the injection site for a prolonged period of time, and a return to normal ovarian cyclicity was associated with the eventual decrease in peripheral drug concentration.
@JR egistered Accepted
Trademark, The Upjohn Company.
for publication
JULY 1974
May 13,
VOL. 10 NO. 1
1974
39
CONTRACEPTION
INTRODUCTION Contraception by administration of a long-acting injectable progestagen preparation, depo-medroxyprogesterone acetate (Depo-Provera @), has been studied extensively (1). The route and frequency of administration of this preparation make it a unique drug for population control. An intramuscular injection of 150 mg at go-day intervals has been demonstrated to have an efficacy rate of 0.25/100 women years in studies of over 70,000 women months of use. Although studied extensively for a number of years, the exact mechanism of action of hormonal (progestagen) contraceptives have not been proven. A number of mechanisms have been suggested for hormonal contraceptives in general (2). Such diverse actions as, alteration of the normal contractile pattern of the female reproductive tract, alteration of cervical mucus secretion, and effects on the hypothalamic-pituitary-gonad axis have been suggested, and are probably involved at least in part. The present experiment was designed to determine the relationship between peripheral (circulating) concentrations of medroxyprogesterone acetate and progesterone following an intramuscular injection of drug. A previous communication (3), which described the development of a medroxyprogesterone acetate radioimmunoassay, reported peripheral concentrations measured during the initial 140 days following an intramuscular injection of 150 mg of depo-medroxyprogesterone acetate in humans. The present study reports data obtained through the time of return of normal ovarian cyclicity, following the intramuscular injection. METHODS Non-pregnant, non-lactating, healthy women between the ages of 19 and 35 years, with a history of regular menstrual cycles (28 f 3 days), and not having been pregnant, or having taken oral contraceptives or other hormone therapy within the previous three months were selected for the study. Subjects accepted were also free of endocrine or gynecologic disease, and were free to use other non-hormonal contraceptive methods while participating in the study. Each subject had 15.0 ml of blood drawn prior to injection and 15.0 ml of blood drawn post-injection on Monday, Wednesday and Friday for an additional 9 specimens, then at weekly intervals until return of ovulation as determined by serum progesterone levels. The 15.0 ml of blood were drawn from a peripheral vein, placed in a non-heparinized container, allowed to clot, centrifuged and serum harvested, then frozen until subsequent analysis.
JULY 1974
VOL. 10 NO. 1
CONTRACEPTION
Provera was quantitated by a radioimmunoassay as described previously (3), and progesterone by a protein binding assay (4)*. In the validation of these assays, it was determined that medroxyprogesterone acetate did not interfere with the progesterone assay and that the naturally circulating progestins did not interfere in the Provera assay, even if present in concentrations of many pg/ml. RESULTS The results of analysis of the human serum for medroxyprogesterone acetate by immunoassay are illustrated in the Figure. Following the injections, at 5-20 days post-injection, concentrations ranged from lo25 ng/ml, then decreased to 5-10 ngfml by 30 days post-injection. The concentrations decreased gradually, with little fluctuation, during the remainder of the study. An exception was the increased concentration found at 63 and 70 days post-injection in one subject. The relatively slow rate of decline in serum medroxyprogesterone acetate concentrations, with only small fluctuations in concentration after 30 days post-injection, indicates a prolonged uniform release of drug from the injection site. The depression of progesterone levels, following the medroxyprogesterone acetate injection, indicates that this activity is biologically effective. The subsequent elevated progesterone concentrations indicate that normal ovarian cyclicity is resumed following this treatment. Medroxyprogesterone acetate concentrations were 5.1, 0.8 and c.5 ng/ml at the time of the first detected rise in plasma progesterone concentration. In this particular series of assays,the minimal detectable concentration of medroxyprogesterone acetate was 0.5 ngfml. All samples were above this level prior to 185 days post-injection. In one of the three patients, levels were below this amount in some of the samples between days 185 and 228, but detectable levels were present in all three subjects within 30 days of the initial progesterone rise. This initial rise in serum progesterone was at 203, 238 and 245 days post-injection. In two of the three subjects, progesterone concentrations in subsequent samples indicated that normal ovarian cyclicity had resumed at that time, in that an apparent second ovulation was detected in these two subjects prior to termination of the study (Table). DISCUSSION The mechanism of action of progestational contraceptives has been suggested, but not conclusively proven to date. In general, the higher *Hormonal activity quantitated by this assay is referred to as progesterone in this manuscript for the sake of clarity. Although this assay is not entirely specific for the steroid progesterone, this molecule accounted for nearly all of the naturally occurring progestins measured by the assay.
JULY 1974
VOL. 10 NO. 1
41
CONTRACEPTION
0
a.
‘33 t13d SWV~SONVN
42
=
JULY 1974 VOL. 10 NO. I
CONTRACEPTION
Table Peripheral Serum Progesterone Concentrations of Patients after an Intramuscular Depo-Medroxyprogesterone Acetate Injection
Subject
Days Post-Injection
Progesterone (ng:/mlserum)
1
0 - 190 196 203 210 218 224 231
co.2 0.7 4.0 2.8 0.4 7.4 co.2
2
0 - 231 238 245 253 260 267
co.2 4.0 0.4 co.2 7.2 2.4
3
0 - 232 245 252 259
co.2 3.0 0.6 co.2
JULY 1974
VOL. 10 NO. 1
43
CONTRACEPTION
dose progestagens inhibit the characteristic mid-cycle ovulatory LH peak, while lower dose regimens apparently control fertility without inhibiting ovulation. Previous studies by Zaiiartuet al. (5) and Homemann (6) have . _ . _ . _ -_. _ lnvestigated the histological appearance ot ovaries tram patients on depomedroxyprogesterone acetate therapy. In general, they found that follicular growth and development, from primordial to Graafian stages, was not impaired. This indirect evidence, and other studies of direct measurements of peripheral serum gonadotrophin concentrations (7,8), indicates that this therapy does not significantly alter basal gonadotrophin levels. Therapy is associated with inhibition of the mid-cycle gonadotrophin peak, and consequently with inhibition of ovulation and corpus luteum formation and function. The present study indicates that a single intramuscular injection of depo-medroxyprogesterone acetate inhibited formation of a functional corpus luteum for a prolonged ($00 days) period of time. During this time,peripheral serum concentrations of medroxyprogesterone acetate, as measured by radioimmunoassay, were detectably elevated. In one subject, ovulation occurred prior to return of drug concentration to non-detectable levels, but after a pronounced reduction in circulating drug levels. The results of this study indicate that drug was released from the injection site for a prolonged period of time, and a return to normal ovarian cyclicity was associated with eventual decreases in peripheral circulating drug concentrations.
44
JULY 1974
VOL. 10 NO. 1
CONTRACEPTION
REFERENCES 1.
Schwallie, P. C. and Assenzo, J. R. Contraceptive use-efficacy study utilizing medroxyprogesterone acetate administered as an intramuscular injection once every 90 days. Fert Steril -24: 331 (1973).
2.
Diczfalusy, E. Mode of action of contraceptive drugs. Gynec 100:136-163 (1968).
3.
Cornette, J. C., Kirton, K. T. and Duncan, G. W. Measurement of medroxyprogesterone acetate (Provera) by radioimmunoassay. J Clin Endo h Metab -33:459-466 (1971).
4.
Sobota, J. T. and Kirton, K. T. Comparison of urinary pregnanediol with plasma progesterone levels to detect ovulation. Obstet Gynec -35:752 (1970).
5.
Zacartu, J., Pupkin, M. and Rosenberg, D. Long-term effect of medroxyprogesterone acetate in human ovarian morphophysiology and sperm transport. Fertil & Steril -21:525-533 (1970).
6.
Homemann, B. and Osler, M. Medroxyprogesterone acetate as a contraceptive. Int .IFertil -17:210-216 (1972).
7.
Goldzieher, J., Kleber, J. and Moses, L. A cross-sectional study of plasma FSH and LH levels in women using sequential, combination and injectable steroid contraceptives over long periods of time. Contraception 2:225 (1970).
8.
Mishell, D., Parlow, A., Talas, M. and El-Habashy, M. Physiologic and morphologic alterations effected by the contraceptive use of depomedroxyprogesterone acetate. In: Proc World Congr Fertil Steril. Sixth Congress, 1970, pp 203. -
JULY 1974
VOL. 10 NO. 1
Am J Obstet
45
Kenneth T. Kirton and James C. Comette Fertility Research, The Upjohn Company Kalamazoo, Michigan
ABSTRACT This study was carried out to determine the relationship between peripheral serum concentrations of medroxyprogesterone acetate (Provera) and progesterone following an intramuscular injection of 150 mg of depomedroxyprogesterone acetate. Medroxyprogesterone acetate concentrations were maximal at 5-20 days post-injection (lo-25 ng/ml), then decreased to 5-10 ng/ml by 30 days post-injection. In general, the concentrations decreased gradually, with little fluctuation, during the remainder of the study (260 days). Medroxyprogesterone acetate concentrations were 5.1, 0.8 and CO.5 ng/ml at the time of the first detected rise in serum progesterone, at 203, 238 and 245 days post-injection. These results indicate that drug was released from the injection site for a prolonged period of time, and a return to normal ovarian cyclicity was associated with the eventual decrease in peripheral drug concentration.
@JR egistered Accepted
Trademark, The Upjohn Company.
for publication
JULY 1974
May 13,
VOL. 10 NO. 1
1974
39
CONTRACEPTION
INTRODUCTION Contraception by administration of a long-acting injectable progestagen preparation, depo-medroxyprogesterone acetate (Depo-Provera @), has been studied extensively (1). The route and frequency of administration of this preparation make it a unique drug for population control. An intramuscular injection of 150 mg at go-day intervals has been demonstrated to have an efficacy rate of 0.25/100 women years in studies of over 70,000 women months of use. Although studied extensively for a number of years, the exact mechanism of action of hormonal (progestagen) contraceptives have not been proven. A number of mechanisms have been suggested for hormonal contraceptives in general (2). Such diverse actions as, alteration of the normal contractile pattern of the female reproductive tract, alteration of cervical mucus secretion, and effects on the hypothalamic-pituitary-gonad axis have been suggested, and are probably involved at least in part. The present experiment was designed to determine the relationship between peripheral (circulating) concentrations of medroxyprogesterone acetate and progesterone following an intramuscular injection of drug. A previous communication (3), which described the development of a medroxyprogesterone acetate radioimmunoassay, reported peripheral concentrations measured during the initial 140 days following an intramuscular injection of 150 mg of depo-medroxyprogesterone acetate in humans. The present study reports data obtained through the time of return of normal ovarian cyclicity, following the intramuscular injection. METHODS Non-pregnant, non-lactating, healthy women between the ages of 19 and 35 years, with a history of regular menstrual cycles (28 f 3 days), and not having been pregnant, or having taken oral contraceptives or other hormone therapy within the previous three months were selected for the study. Subjects accepted were also free of endocrine or gynecologic disease, and were free to use other non-hormonal contraceptive methods while participating in the study. Each subject had 15.0 ml of blood drawn prior to injection and 15.0 ml of blood drawn post-injection on Monday, Wednesday and Friday for an additional 9 specimens, then at weekly intervals until return of ovulation as determined by serum progesterone levels. The 15.0 ml of blood were drawn from a peripheral vein, placed in a non-heparinized container, allowed to clot, centrifuged and serum harvested, then frozen until subsequent analysis.
JULY 1974
VOL. 10 NO. 1
CONTRACEPTION
Provera was quantitated by a radioimmunoassay as described previously (3), and progesterone by a protein binding assay (4)*. In the validation of these assays, it was determined that medroxyprogesterone acetate did not interfere with the progesterone assay and that the naturally circulating progestins did not interfere in the Provera assay, even if present in concentrations of many pg/ml. RESULTS The results of analysis of the human serum for medroxyprogesterone acetate by immunoassay are illustrated in the Figure. Following the injections, at 5-20 days post-injection, concentrations ranged from lo25 ng/ml, then decreased to 5-10 ngfml by 30 days post-injection. The concentrations decreased gradually, with little fluctuation, during the remainder of the study. An exception was the increased concentration found at 63 and 70 days post-injection in one subject. The relatively slow rate of decline in serum medroxyprogesterone acetate concentrations, with only small fluctuations in concentration after 30 days post-injection, indicates a prolonged uniform release of drug from the injection site. The depression of progesterone levels, following the medroxyprogesterone acetate injection, indicates that this activity is biologically effective. The subsequent elevated progesterone concentrations indicate that normal ovarian cyclicity is resumed following this treatment. Medroxyprogesterone acetate concentrations were 5.1, 0.8 and c.5 ng/ml at the time of the first detected rise in plasma progesterone concentration. In this particular series of assays,the minimal detectable concentration of medroxyprogesterone acetate was 0.5 ngfml. All samples were above this level prior to 185 days post-injection. In one of the three patients, levels were below this amount in some of the samples between days 185 and 228, but detectable levels were present in all three subjects within 30 days of the initial progesterone rise. This initial rise in serum progesterone was at 203, 238 and 245 days post-injection. In two of the three subjects, progesterone concentrations in subsequent samples indicated that normal ovarian cyclicity had resumed at that time, in that an apparent second ovulation was detected in these two subjects prior to termination of the study (Table). DISCUSSION The mechanism of action of progestational contraceptives has been suggested, but not conclusively proven to date. In general, the higher *Hormonal activity quantitated by this assay is referred to as progesterone in this manuscript for the sake of clarity. Although this assay is not entirely specific for the steroid progesterone, this molecule accounted for nearly all of the naturally occurring progestins measured by the assay.
JULY 1974
VOL. 10 NO. 1
41
CONTRACEPTION
0
a.
‘33 t13d SWV~SONVN
42
=
JULY 1974 VOL. 10 NO. I
CONTRACEPTION
Table Peripheral Serum Progesterone Concentrations of Patients after an Intramuscular Depo-Medroxyprogesterone Acetate Injection
Subject
Days Post-Injection
Progesterone (ng:/mlserum)
1
0 - 190 196 203 210 218 224 231
co.2 0.7 4.0 2.8 0.4 7.4 co.2
2
0 - 231 238 245 253 260 267
co.2 4.0 0.4 co.2 7.2 2.4
3
0 - 232 245 252 259
co.2 3.0 0.6 co.2
JULY 1974
VOL. 10 NO. 1
43
CONTRACEPTION
dose progestagens inhibit the characteristic mid-cycle ovulatory LH peak, while lower dose regimens apparently control fertility without inhibiting ovulation. Previous studies by Zaiiartuet al. (5) and Homemann (6) have . _ . _ . _ -_. _ lnvestigated the histological appearance ot ovaries tram patients on depomedroxyprogesterone acetate therapy. In general, they found that follicular growth and development, from primordial to Graafian stages, was not impaired. This indirect evidence, and other studies of direct measurements of peripheral serum gonadotrophin concentrations (7,8), indicates that this therapy does not significantly alter basal gonadotrophin levels. Therapy is associated with inhibition of the mid-cycle gonadotrophin peak, and consequently with inhibition of ovulation and corpus luteum formation and function. The present study indicates that a single intramuscular injection of depo-medroxyprogesterone acetate inhibited formation of a functional corpus luteum for a prolonged ($00 days) period of time. During this time,peripheral serum concentrations of medroxyprogesterone acetate, as measured by radioimmunoassay, were detectably elevated. In one subject, ovulation occurred prior to return of drug concentration to non-detectable levels, but after a pronounced reduction in circulating drug levels. The results of this study indicate that drug was released from the injection site for a prolonged period of time, and a return to normal ovarian cyclicity was associated with eventual decreases in peripheral circulating drug concentrations.
44
JULY 1974
VOL. 10 NO. 1
CONTRACEPTION
REFERENCES 1.
Schwallie, P. C. and Assenzo, J. R. Contraceptive use-efficacy study utilizing medroxyprogesterone acetate administered as an intramuscular injection once every 90 days. Fert Steril -24: 331 (1973).
2.
Diczfalusy, E. Mode of action of contraceptive drugs. Gynec 100:136-163 (1968).
3.
Cornette, J. C., Kirton, K. T. and Duncan, G. W. Measurement of medroxyprogesterone acetate (Provera) by radioimmunoassay. J Clin Endo h Metab -33:459-466 (1971).
4.
Sobota, J. T. and Kirton, K. T. Comparison of urinary pregnanediol with plasma progesterone levels to detect ovulation. Obstet Gynec -35:752 (1970).
5.
Zacartu, J., Pupkin, M. and Rosenberg, D. Long-term effect of medroxyprogesterone acetate in human ovarian morphophysiology and sperm transport. Fertil & Steril -21:525-533 (1970).
6.
Homemann, B. and Osler, M. Medroxyprogesterone acetate as a contraceptive. Int .IFertil -17:210-216 (1972).
7.
Goldzieher, J., Kleber, J. and Moses, L. A cross-sectional study of plasma FSH and LH levels in women using sequential, combination and injectable steroid contraceptives over long periods of time. Contraception 2:225 (1970).
8.
Mishell, D., Parlow, A., Talas, M. and El-Habashy, M. Physiologic and morphologic alterations effected by the contraceptive use of depomedroxyprogesterone acetate. In: Proc World Congr Fertil Steril. Sixth Congress, 1970, pp 203. -
JULY 1974
VOL. 10 NO. 1
Am J Obstet
45