In vivo metabolism of progestins. V. The effect of protocol design on the estimated metabolic clearance rate and volume of distribution of medroxyprogesterone acetate in women.

The metabolism of the synthetic progestin, [3H]medroxyprogesterone acetate (MPA), was studied in women using a single injection technique. Computer-implemented analysis was used to calculate the MCR (MCRMPA) and volume of distribution (VoMPA) from the steroid disappearance curve. The value of an objective curve-fitting technique was demonstrated. The effect of protocol design (number and frequency of samples) on these metabolic parameters was evaluated. The estimation of VoMPA was most sensitive to alterations of experimental design and biological variability, while MCR was less easily effected. The MCRMPA of 1668 +/- 146 (SEM) liters/day was lower than that for progesterone but higher than that of another synthetic steroid, dexamethasone. Treatment of women with MPA or aminoglutethimide, two drugs known to increase the rates of testosterone and dexamethasone metabolism, respectively, did not alter MCRMPA. From these observations we conclude 1) with the single injection technique it is difficult to estimate Vo of compounds such as MPA which are rapidly metabolized and 2) the MCRMPA was higher than expected and less susceptible to drug-induced changes than the clearance of other steroids.

Serum medroxyprogesterone acetate (MPA) concentrations and ovarian function following intramuscular injection of depo-MPA.

A sensitive radioimmunoassay measuring serum medroxyprogesterone acetate (MPA) has been developed in order to measure and correlate serum MPA concentrations and ovarian function in women following im administration of deop-MPA (DMPA), employing goat anti-MPA-3-(O-carboxymethyl) oxime-bovine serum albumin and MPA-3-(O-carboxymethyl) imino-125I-iodohistamine. In the 3 women studied, im injection of 150 mg of DMPA yielded brief initial serum MPA concentrations ranging from 1.5 to 3 ng/ml for a few days. Serum MPA concentrations gradually declined and remained relatively constant at about 1 ng/ml for 2 to 3 months, declined gradually thereafter reaching 0.2 ng/ml during the 6th month and became undetectable (less than 0.02 ng/ml) about 7-1/2 to 9 months following administration. Serum estradiol remained at early to midfollicular phase levels for 4 to 6 months after DMPA injection and rose to preovulatory levels when serum MPA levels fell below 0.5 to 0.25 ng/ml. Ovulation, however, as evidenced by serum progesterone concentrations did not occur, apparently due to suppression of the LH peak by positive feedback inhibition. Prolonged inhibition of cyclic ovarian function following DMPA injection is caused by slow MPA absorption and persists until serum MPA levels have decreased below 0.1 ng/ml or become undetectable about 7 to 9 months after DMPA administration.

PIP: Serum medroxyprogesterone acetate (MPA) concentrations were measured by a newly developed, highly sensitive, radioimmunoassay technique, and ovarian function was evaluated in 3 women after a single im injection of MPA (150 mg). Initial MPA concentrations ranged from 1.5 to 3 ng/ml for the 1st few days, and then gradually declined to a relatively constant level of about 1 ng/ml for 2-3 months. During the 6th month, MPA concentrations had declined to about .2 ng/ml, and became undetectable between 7!-9 months. Serum estradiol levels remained at early or midfollicurlar phase values for 4-6 months following injection, and then increased to preovulatory values (.25-.5 ng/ml). However, ovulation did not occur as determined by serum progesterone concentrations. Prolonged suppression of ovarian function by depo-MPA is due to the slow release of MPA; from the injection site.

Effects of progestins on estradiol receptor levels in human endometrium.

Medroxyprogesterone acetate (Provera) was administered orally during 2-4 days to women undergoing endometrial curettage during the follicular phase of the menstrual cycle. Estradiol (E2) receptor levels were estimated from the amounts of 2H-E2 tightly bound in nuclei after incubation of endometrial tissue with an excess of the labeled hormone. An average value (9 subjects) of 1.5 pmole E2/mg DNA +/- 0.7 (mean +1- SD) was found. This value is significantly lower than the average E2 receptor levels in proliferative endometrium of untreated subjects (3.2 +/- 1.3, n = 33) and equals the level observed in the early secretory phase (1.5 +/- 0.5, n = 5). These results indicate that one of the progestin effects on human endometrium is the reduction of E2 receptor levels.

Comparison of mass spectrometry and radioimmunoassay to measure medroxyprogesterone acetate in patients with endometrial cancer.

Serum medroxyprogesterone acetate (MPA) was measured by radioimmunoassay (RIA) and gas chromatography-mass spectrometry (GC-MS) in patients with endometrial cancer. Samples were obtained 3, 6 and 24 h after the oral administration of 100 or 200 mg MPA once a day. The levels obtained by GC-MS were lower (median 16-29%) than those obtained by RIA, which is probably attributable to the presence of metabolites interfering with the RIA. Two commercial MPA formulations gave different MPA serum levels by both RIA and GC-MS. The levels obtained by GC-MS were so low that frequently only partial saturation of the endometrial progesterone receptor may be achieved which may explain why high oral doses are needed to produce optimum therapeutic response.

Growth of human aortic smooth muscle cells cultured with human serum is retarded when serum lipids are lowered by medroxyprogesterone.

Human aortic smooth muscle cells were cultured in the presence of sera from 7 normolipidemic women before and after treatment with high-dose medroxyprogesterone acetate, which caused 16% and 25% decreases in serum cholesterol and HDL-cholesterol concentrations, respectively. As assessed by cell counting and by DNA determination the growth of the cells was retarded significantly in the presence of sera taken after the treatment. At the same time, there were no marked changes in the incorporation rate of [3H]proline into collagen or [3H]glucosamine into hyaluronic acid by the cells. The results indicate that: (1) the mitogenicity of human serum can be altered by drug treatment of serum donors, (2) simultaneously with a lowering of serum lipids in man in vivo, a decreased mitogenicity of sera occurs in vitro.

Medroxyprogesterone acetate does not perturb the profile of steroid metabolites in urine during pregnancy.

The plasma concentrations of medroxyprogesterone acetate (MPA) in 14 women administered the progestagen for threatened abortion during the first 6 weeks of pregnancy were measured by specific radioimmunoassay. Treatment (52 nmol orally every 6 h) was continued to 18 weeks of gestation. The mean plasma concentration of MPA rose rapidly during day 1 of treatment to 14.1 +/- 1.84 nmol/l. It reached 21.5 +/- 2.3 nmol/l by 7 days and subsequently stabilized at around 26.8 +/- 5.0 nmol/l by the end of week 2. Urinary steroid profiles were determined by gas-liquid chromatography and mass spectrometry for six of the MPA-treated women and compared with those of six untreated women of similar gestational age. No differences were detected between the two groups of women, suggesting that the administration of MPA during pregnancy did not alter qualitatively or quantitatively the metabolism and excretion into urine of progesterone and oestrogens.

Effect of ovarian steroids on vasopressin secretion.

In normally menstruating women plasma vasopressin concentrations vary with the stage of the cycle and are highest at the time of ovulation and lowest at the onset of menstruation. To determine whether this is the result of changes in the circulating concentrations of ovarian steroids, vasopressin concentrations were determined in six postmenopausal women given oestrogen and progestogen. An increase in plasma oestradiol concentrations to 299 +/- 97.8 pmol/l augmented vasopressin release. Administration of medroxyprogesterone did not influence vasopressin concentrations but when given in combination with oestrogen a fall was observed. Thus it appears that ovarian steroids can modulate vasopressin release.

Plasma concentrations of medroxyprogesterone acetate and megesterol acetate during long-term follow-up in patients treated for metastatic breast cancer.

A total of 32 patients with metastatic breast cancer responding with at least disease stabilization to treatment with two commercially available preparations of medroxyprogesterone acetate (MPA) or one preparation of megestrol acetate (MA) were followed for their plasma concentrations. The MPA and MA were measured by HPLC. MPA from Upjohn and Farmitalia was given to 12 patients (median age, 61 years; median follow-up, 20 weeks) and 8 patients (54 years, 16 weeks), respectively, on a schedule of 1000 mg daily i.m. for 10 days followed by 200 mg t.i.d.p.o. for the remainder of the treatment course. The peak concentrations (means, 163 vs 97 ng/ml), the time to peak levels (medians, 3 vs 10 weeks), and the areas under the concentration curves from time 0 to 24 weeks (means, 2400 vs 1868 ng/ml X weeks) were significantly different in the respective treatment groups (t-test; significance level, 0.05). MA from Bristol-Myers was administered orally in one daily dose of 160 mg throughout the treatment course in 12 patients (median age, 51 years; median follow-up, 20 weeks). A mean MA peak concentration of 218 ng/ml was reached after a median of 7 days. Plateau plasma levels were higher for MA than MPA.

An enzyme linked immunosorbent assay (ELISA) for plasma medroxyprogesterone acetate (MPA).

A single extraction fixed antigen enzyme-linked immunosorbent assay (ELISA) that can be completed in less than 24 h is described for the measurement of medroxyprogesterone acetate (MPA) in plasma. MPA is covalently coupled to bovine thyroglobulin and passively adsorbed in guanidine hydrochloride to a standard 96-well microtitre plate where it competes with MPA in the extracted plasma sample for goat anti-MPA. Antibody binding to the solid phase is determined via binding of a horse-radish peroxidase second antibody which reacts colorimetrically with its substrate. The reaction is stopped by addition of 1.25 M H2SO4 and absorbance read at 492 nm. All steps except for sample addition and extraction can be performed on an automatic ELISA processing machine. The assay is sensitive, specific and precise, with intra- and inter-assay coefficients of variation of less than 10 and 15%, respectively. Assay sensitivity is 0.08 ng/ml. The assay follows established methodology for other assays in this laboratory which assists standardization, cost structure and sample throughput and thus is a useful alternative to radioimmunoassays for the determination of MPA in plasma.

Galactorrhea and hyperprolactinemia during treatment of polycystic ovary syndrome.

The serum concentration of prolactin and the presence of galactorrhea were evaluated systematically in a prospective study of the effect of medroxyprogesterone acetate (MPA) in polycystic ovary syndrome (PCO). In 21 patients, the diagnosis of PCO was made by laparoscopy. Three women presented with galactorrhea and increased prolactin levels, 2 had galactorrhea with normal prolactin levels, and 3 had an isolated elevation in the serum concentration of prolactin. Treatment with MPA induced galactorrhea in 10 additional patients. Elevated levels of prolactin were detected in 18 of the patients during treatment. There was no correlation between the score for galactorrhea and the level of prolactin. Tomograms of the sella turcica were abnormal in 3 of 8 patients with hyperprolactinemia. The authors conclude that galactorrhea and/or hyperprolactinemia are important side effects of MPA in patients with PCO.

Short-term effects of estrogen and progestin on blood pressure of normotensive postmenopausal women.

Blood pressure rises in women with increasing age, possibly related to the decrease in production of female hormones that accompanies menopause. Although estrogen or progestin administration alone consistently does not lower blood pressure in postmenopausal women, possible interactions of these two hormones in affecting blood pressure are not well understood. We studied 12 surgically postmenopausal, normotensive women, aged 51 +/- 2 years (SEM). Treatment for each subject consisted of 1 week each of placebo, estrogen (conjugated equine estrogens, 2.5 mg/day), progestin (medroxyprogesterone acetate, 60 mg/day), and combined estrogen and progestin, given in varied order. At the end of each week, auscultatory blood pressures were measured while patients were seated. Neither estrogen nor progestin alone either increased or decreased blood pressure significantly, whereas combined estrogen and progestin lowered systolic, diastolic, and mean blood pressures 6 to 7 mm Hg (P less than .05). Treatment order was unrelated to the change in blood pressure values. The authors suggest that administering progestin with estrogen may be more effective in lowering blood pressure than either hormone alone in postmenopausal women.

Comparative pharmacokinetics of medroxyprogesterone acetate administered by oral and intramuscular routes.

The present study was undertaken to elucidate (1) the relationship between plasma concentration of medroxyprogesterone acetate (MPA; Clinovir) administered by the PO and the IM routes; and (2) the relationship between dose and plasma concentration of MPA. Nineteen patients entered the study. In each patient the plasma concentration was monitored after a single PO and IM administration of MPA at the following dose levels: 100 mg (5 patients), 400 mg (5 patients), 800 mg (5 patients) and 1,200 mg (4 patients). The time interval between PO and the IM administration was 1 week. The results show (1) a very large interindividual variation in plasma concentration; (2) increasing plasma concentration with both PO and IM dose; (3) after the IM administration plasma levels are steady or increase slightly within the test period; (4) after the oral administration the concentration increases rapidly to reach a peak before 2-7 h and subsequently decreases again, peak concentrations being 2-10 times higher than after IM administration; and (5) within the test periods the plasma concentration x time (0-168 h) is comparable with the two methods of administration.

Medroxyprogesterone acetate (MAP) plasma levels after simultaneous oral and intramuscular administration in cancer patients.

After simultaneous administration of medroxyprogesterone acetate (MAP) 1,000 mg PO and 1,000 mg IM to ten cancer patients, we observed mean plasma MAP profiles that could be exactly superimposed on the two absorption/decay curves obtained after administration of single doses IM or PO. Treatment with MAP given simultaneously by the IM and PO routes may be effective in overcoming the drawbacks of both routes, and can also more reliably guarantee plasma levels in the therapeutic range.

Bioavailability of medroxyprogesterone acetate from three oral dosage formulations.

The bioavailability of three formulations of medroxyprogesterone acetate (MPA) was assessed in 30 healthy male volunteers in a three-way, open-label, cross-over-designed trial. Each subject received one Provera 500-mg tablet, one Farlutal 500-mg tablet, and one Provera 500-mg granule packet according to a randomized schedule, with each treatment separated by a 21-day washout period. Serum MPA levels were determined using both radioimmunoassay (RIA) and high-performance liquid chromatography techniques. Based on the results of RIA analysis, Farlutal tablets produced significantly lower serum MPA concentrations compared with Provera tablets at most sampling times, resulting in statistically lower AUC0-144 for the Farlutal tablet (544 vs 768 ng.hr/ml; -29.2%). The Farlutal tablet also had a significantly lower maximum concentration than the Provera tablet (27.8 vs 47.4 ng/ml; -41.4%). However, there was no significant difference in time of maximum concentration between the tablet formulations (3.71 vs 3.41 hr), indicating that the rates of absorption of the two tablet formulations were comparable. Provera granules provided significantly higher serum MPA levels than Provera tablets at 0.5, 1, 1.5, 2, and 6 hours, and the AUC0-144 for Provera granules was higher by 5.47% (810 vs 768 ng.hr/ml). There were no differences in terminal elimination rate constants among the dosage forms. No significant adverse events were noted during the trial. The relative bioavailabilities of Provera granules and Farlutal tablets were 105% and 71.2%, respectively, compared with Provera tablets.

Medroxyprogesterone acetate (MAP) plasma levels after multiple high-dose administration in advanced cancer patients.

Medroxyprogesterone acetate plasma levels were measured in advanced cancer patients after multiple PO or IM administration (500, 1000, 2000, 3000, 4000, and 5000 mg/day PO and 500, 1000, 2000 mg/day IM for 30 days). After PO administration, the plasma concentration rises quickly and plateau level is reached in 4-10 days. Discontinuation of the treatment produces a fast decay (t1/2 = 62.4 h) of the drug levels. When medroxyprogesterone acetate is given IM plasma levels, steadily increase and after drug discontinuation no noticeable decay is observed for at least 6 months; plateau plasma levels are about three times higher than after the corresponding PO treatment. Extremely high interpatient variation in bioavailability is present with both administration routes. These data may well rationalize the results of previous clinical trials and will help in planning treatment schedules.

Medroxyprogesterone acetate (MAP) and tamoxifen (TMX) plasma levels after simultaneous treatment with 'low' TMX and 'high' MAP doses.

Plasma levels of medroxyprogesterone acetate (MAP), tamoxifen (TMX) and its major metabolites, 4-hydroxy TMX and desmethyl TMX, were determined in five patients with advanced breast cancer following simultaneous MAP (2,000 mg/day) and TMX (20 mg/day) oral therapy. The interindividual variance in MAP plasma levels was wide; the mean plasma levels of both drugs were nearly identical, despite the large difference in the administered doses.

Influence of aminoglutethimide on the metabolism of medroxyprogesterone acetate and megestrol acetate in postmenopausal patients with advanced breast cancer.

In this study the influence of amino-glutethimide (AG) on the disposition of medroxyprogesterone acetate (MPA) and megestrol acetate (MA) was studied. When 1,000 mg AG daily was supplementally given to six patients on chronic treatment with MPA (1,000 mg/day) or MA (160 mg/day), mean serum levels of progestin were reduced by 74% as compared with control levels (P less than 0.03). AG did not change the blood clearance rate of MPA when the latter was given i.v. This discrepancy between AG's influence on oral and parenteral progestin disposition could be explained by pharmacokinetic properties of the progestins, and our results suggest that AG stimulates the metabolism of progestins. The decrease in MPA and MA serum levels was accompanied by an increase in serum cortisol, sex hormone-binding globulin (SHBG) and testosterone levels. This suggests that AG reduces the biological activity of progestins.

Lack of correlations between plasma concentration of medroxyprogesterone acetate, hypothalamic-pituitary function, and tumour response in patients with advanced breast cancer.

Plasma medroxyprogesterone acetate (MPA) concentrations were measured in 61 patients with advanced breast cancer, after 3 weeks' treatment using 200 mg PO 8-hourly, to determine whether the previously reported wide interpatient variations correlated with tumour response or toxicity. Seventeen patients (28%) responded to the drug, and their mean plasma MPA concentration was 97 ng/ml +/- 68 SD, compared with 115 ng/ml +/- 87 SD for the patients whose disease progressed. Side-effects attributed to MPA were seen in 18 patients, who had a mean drug concentration of 113 ng/ml +/- 104 SD. This was not significantly higher than that of the patients who did not experience drug toxicity. Because of a suggestion that some of the antitumour activity of the drug could be mediated via an effect on the hypothalamic-pituitary axis, we also measured plasma FSH, LH, and prolactin concentrations after the 3-week treatment with MPA, but found no correlations with either drug concentration or tumour response. These results indicate that with the present treatment schedule the monitoring of plasma MPA concentrations has no role in routine practice and suggest that the inherent sensitivity of the tumour to progesterone is probably the major determinant of response.

Combination of 19-nortestosterone-hexyloxyphenylpropionate (Anadur) and depot-medroxyprogesterone-acetate (Clinovir) for male contraception.

Because monotherapy with 19-nortestosterone hexyloxyphenylpropionate (Anadur, Pharmacia Arzneimittel, Ratingen, Federal Republic of Germany) suggested improved results for male contraception compared with available testosterone esters, it was tested for induction of complete azoospermia when combined with depot-medroxyprogesterone acetate (DMPA, Clinovir, Upjohn GmbH, Heppenheim, Federal Republic of Germany). Twelve men were treated for 7 weeks with weekly intramuscular (IM) injections of 200 mg Anadur followed by 3-weekly IM injections of Anadur up to week 15. Clinovir (250 mg) IM was administered at the start of treatment and during weeks 6 and 12. Anadur and Clinovir suppressed serum gonadotropins. Although serum testosterone declined steeply, in general, libido and potency were not impaired. Sperm concentrations were reduced significantly after 3 weeks of treatment. Lowest sperm counts were seen during week 8 of follow-up, when only 2 volunteers showed measurable sperm counts of 2.1 and 3.0 X 10(6)/ml, with a declining tendency. After 43 weeks, sperm concentrations were still below pretreatment range in 2 men, but later returned to pretreatment values. Computerized sperm motion analysis revealed that motility parameters in the residual sperm were reduced. In vitro analysis excluded a direct effect of medroxyprogesterone acetate in seminal plasma on sperm motion. The data indicate that the combination of Anadur with Clinovir increases the rate of azoospermia in normal volunteers seen under Anadur monotherapy, although the goal of azoospermia in all participants was not quite achieved.

A preliminary pharmacokinetic and pharmacodynamic evaluation of depot-medroxyprogesterone acetate and norethisterone oenanthate.

PIP: 2 populations attending WHO centers, one in Sweden and one in India, participated in a comparative, pilot trial of 2 increasingly popular injectable progestin-only female contraceptives, Depo-Provera and Norigest. The purpose of the study was to assess the pharmacokinetic and pharmacodynamic properties of the 2 formulations (depot medroxyprogesterone acetate and norethisterone enanthate). Differences were found between Swedish women and Indian women in their reactions to the 2 drugs: 1) Norigest was detectable in blood samples a significantly shorter time after injection of the agent in Indian women than in Swedish women; this difference was not apparent with Depo-Provera. 2) Although there was no difference at the 2 centers in the time of ovulation return for subjects receiving Norigest, 0 of 4 Swedish women ovulated more than 156 days after Depo-Provera injection, whereas all 4 Indian women ovulated within 73 days of Depo-Provera injection; in the Swedish women, the levels of medroxyprogesterone were undetectable at time of return to ovulation, whereas Indian women had levels of .6 ng/ml when ovulation resumed. 3) In both cultures, Depo-Provera users had significantly more episodes of bleeding and spotting than Norigest users. This preliminary report emphasizes the variety of responses possible to injection of different contraceptive progestins among various populations and points to the need for further culturally comparative studies.^ieng