Synthesis and biological properties of 9-deoxo-16,16-dimethyl-9-methylene-PGE2

The in vivo monkey uterine stimulating potency of 9-deoxo-16,16-dimethyl-9-methylene-PGE₂ is similar to that of 16,16-dimethyl-PGE₂ and approximately 15 times that of PGE₂. Low doses of this compound stimulated uterine contractions when administered vaginally. Pregnancy was terminated prematurely following subcutaneous, intramuscular or vaginal suppository treatment. Estimates of potential for gastrointestinal side effects using the rat enteropooling assay and in vivo monkey effects indicate that diarrhea will be substantially reduced with retention of uterine stimulating potency.     

Reassessment of systemic administration of prostaglandins for induction of midtrimester abortion

The present investigation was undertaken to evaluate the abortifacient efficacy of vaginal and intramuscular administration of different dose schedules of the 15-methyl analogues of prostaglandin F_2α.1. . Both 15-methyl-PGF_2α and 15-methyl-PGF_2α methyl ester can be absorbed from the vagina in sufficient amounts to induce abortion. The potency of the methyl ester was approximately twice that of the free acid. The most successful treatment schedule consisted of an initial dose of 0.5 mg of the methyl ester followed by 1.0 or 2.0 mg every third hour. On this treatment all patients aborted within 24 hours.2. . Initially 200 μg of 15-methyl-PGF_2α was given. The dose was increased to 400 μg or occasionally to 500 μg depending on the effect and tolerance of the patient and repeated every third hour. The treatment schedule resulted in a 100 per cent abortion rate and the mean induction-abortion interval was 16.1 hours.Both routes were associated with a higher frequency of side effects than that reported for intra-amniotic administration of 15-methyl-PGF_2α. It seems justified to conclude that the intra-amniotic route is preferable after the 14th week when the uterine cavity is easy to puncture but that vaginal or intramuscular injections of the compounds could be an alternative in late first trimester and early second trimester cases.     

Midtrimester and missed abortion treated with intramuscular 15 (S)-15 methyl PGF2α

Abortion was successfully induced in 79 of 80 patients in midtrimester, by the serial administration of 250 μg of 15 (S)-15 methyl PGF₂α intramuscularly every second hour until abortion occurred. All 12 patients with missed abortion and 87% of the legal abortion patients aborted within 24 hours. The average period until abortion occurred in the missed abortion group was 8.2 hours (± 4.5 SD), and in the legal abortion group 16.4 hours (± 7.3 SD). All the patients were given prophylactic treatment for vomiting, using prochlorperazine. The average number of episodes of vomiting was 2.8 per patient. All but 3 patients were given loperamide or diphenoxylate for “diarrhoea”. The average number of episodes of diarrhoea was 2.5 per patient. The frequency of complications was low apart from a case of low uterine rupture.     

Vaginally administered 16, 16-dimethyl-prostaglandin E2 as an agent for pre-operative cervical dilatation

Twenty-one women in the 10th–12th week of pregnancy were treated prior to vacuum aspiration with vaginal suppositories containing 16, 16-dimethyl-PGE₂ (free acid). An average total dose of 3.4 mg led to abortion or adequate cervical dilatation in all patients. Based upon previous experience with the compound, no prophylactic anti-emetic or anti-diarrhetic medication was given. Gastrointestinal side effects were minimal. Excessive bleeding was not observed. In two cases, slight temperature elevation was noted prior to abortion. The low incidence of side effects in combination with the effectiveness of the compound help to make this method an attractive therapeutic adjunct to vacuum aspiration beyond the 10th week of gestation. Under the experimental conditions of this study, the results suggest that vaginally administered 16, 16-dimethyl-PGE₂ can be a safe and effective method for cervical dilatation before vacuum aspiration.     

Vaginally administered 16, 16-dimethyl-prostaglandin E2 as an agent for pre-operative cervical dilatation

Twenty-one women in the 10th–12th week of pregnancy were treated prior to vacuum aspiration with vaginal suppositories containing 16, 16-dimethyl-PGE₂ (free acid). An average total dose of 3.4 mg led to abortion or adequate cervical dilatation in all patients. Based upon previous experience with the compound, no prophylactic anti-emetic or anti-diarrhetic medication was given. Gastrointestinal side effects were minimal. Excessive bleeding was not observed. In two cases, slight temperature elevation was noted prior to abortion. The low incidence of side effects in combination with the effectiveness of the compound help to make this method an attractive therapeutic adjunct to vacuum aspiration beyond the 10th week of gestation. Under the experimental conditions of this study, the results suggest that vaginally administered 16, 16-dimethyl-PGE₂ can be a safe and effective method for cervical dilatation before vacuum aspiration.     

Reassessment of systemic administration of prostaglandins for induction of midtrimester abortion

This investigation was conducted to evaluate the abortifacient efficacy of vaginal and intramuscular administration of different dose schedules of the 15-methyl analogues of prostaglandin F2 alpha. Both 15-methyl PGF2 alpha and 15-methyl PGF methyl ester can be absorbed from the vagina in sufficient amounts to induce abortion. The potency of the methyl ester was approximately twice that of the free acid. The most successful treatment schedule consisted of an initial dose of 0.5 mg of the methyl ester followed by 1.0 or 2.0 mg every third hour. On this treatment all patients aborted within 24 hours. Initially 200 ug of 15-methyl-PGF2 alpha was given. The dose was increased to 400 ug or occassionally to 500 ug depending on the effect and tolerance of the patient and repeated every third hour. The treatment schedule resulted in a 100% abortion rate and the mean induction-abortion interval was 16.1 hours. Both routes were associated with a higher frequency of side effects than that reported for intraamniotic administration of 15-methyl-PGF2 alpha. It seems justified to conclude that the intraamniotic route is preferable after the 14th week when the uterine cavity is easy to puncture, but that vaginal or intramuscular injections of the compounds could be an alternative in late first trimester and early second trimester cases.     

Method for quantitative analysis of 16, 16-dimethyl-prostaglandin E2 from plasma using deuterated carrier and gas chromatography-mass spectrometry.

The preparation of 3,3,4,4-²H₄16,16-dimethyl-prostaglandin E₂ (PGE₂), 16,16-dimethyl-5,6-didehydro-PGE₂, and 5,6-³H₂16,16-dimethyl-PGE₂ is described. These compounds have been used for development of a gas-liquid chromatography-mass spectrometry method for quantitative determination of corresponding nondeuterated prostaglandin. The method is based on addition of a known amount of carrier to the sample and after purification and derivation the ratio between the protium and deuterium form is measured in the mass spectrometer. With this technique 40 pg of 16,16-dimethyl-PGE₂ can be determined with a precision of ±2.6%.     

Prostaglandin-induced pregnancy termination: further studies using gemeprost (16,16 dimethyl-trans-delta 2-PGE1 methyl ester) vaginal pessaries in the early second trimester

The use of gemeprost (16,16 dimethyl-trans-delta 2-PGE1 methyl ester) vaginal pessaries for the termination of pregnancy in the early second trimester has been further investigated. Of 113 women between 12 and 16 weeks gestation, 93 (82%) aborted within 24 hours of the administration of 4.4 +/- 0.1 1 mg gemeprost pessaries. The mean induction-abortion interval was 881 +/- 31 minutes. Successful abortion was achieved in 16 of the remaining 20 women after a second course of gemeprost pessaries without the need for oxytocin supplementation. There were no serious complications. Crampy abdominal pain and vaginal bleeding started after 275 and 756 minutes respectively. Twenty-two (19%) patients did not require pain relief during treatment, but 90 (80%) required parenteral opiates. Vomiting and diarrhoea occurred in 16 (14%) and 23 (20%) cases respectively. The safe induction of therapeutic abortion in 96% of women using vaginal prostaglandin alone offers an acceptable alternative to surgical evacuation in the early second trimester.     

Administration of 15-methyl-prostaglandin F2α as a pre-operative means of cervical dilatation

Pre-operative dilatation of the cervix prior to vacuum aspiration was accomplished in 67 volunteers by extra-amniotic or intra-muscular administration of 15(S)-15-methyl-PGF_2α (15-me-PGF_2α). Ninety-four per cent of the patients were in the 11th–13th week of gestation and 61% were nulliparae. A single extra-amniotic instillation (mean of 400 μg) or 3 intramuscular injections (300–800 μg per injection) of the compound induced a satisfactory outcome in terms of either abortion or sufficient dilatation of the cervix in 81% of the patients. In the remaining cases, the cervix was found at operation to be open for 7–9 mm which simplified the process of additional instrumental dilatation. In general the outcome of the trial turned the operation into an easy and safe procedure. Vacuum aspiration was performed in all cases after a mean time lag of 16 hours following the onset of the treatment. Extra-amniotic administration was associated with a low incidence of gastro-intestinal side-effects, but there was a transient and moderate degree of uterine pain reaction. The intramuscular route was technically more simple and caused less uterine pain but the high incidence of vomiting and diarrhoea constituted a clinical disadvantage. In late first trimester abortions, particularly cases where the uterus appears larger than expected, it is believed that dilatation of the cervix by PG prior to vacuum aspiration is a sound clinical indication. The method offers definite advantages that compensate for the price of some minor side-effects.     

Rupture of the uterus following treatment with 16-16-dimethyl E 2 prostaglandin vagitories

Rupture of the uterine body was found after induction of therapeutic abortion with vaginal suppositories containing 16,16-dimethyl prostaglandin E 2 in a 20-year-old primigravida. A short discussion is given on the cervical complications that can occur after prostaglandin induction of abortion, stating that rupture of the uterine body also can be seen. So far, no prostaglandin compound seems to avoid such complications.     

Serial intramuscular injections of 15(S)-15-methyl-prostaglandin F2α in the induction of abortion

Abortion was successfully induced in 62 of 68 patients in the 9th to the 26th week of pregnancy by serial intramuscular administration of 15(S)-15-methyl-prostaglandin F_2α (15-ME-PGF_2α). In 6 patients who failed to abort after 24 hours of prostaglandin administration, a concomitant infusion of oxytocin was initiated; 5 of these patients aborted within 12 hours of the combined therapy. A single patient failed to abort, even with the combined therapy, and underwent surgical evacuation. The mean abortion time in the 67 successful inductions was 14.56 hours. Parous patients aborted somewhat faster, mean 13.98 hours, as compared to nulliparous patients, mean 15.02 hours, but this difference was not statistically significant. In this study initial intramuscular injection of 100 μg 15-ME-PGF_2α was followed in 1 hour by 250 μg and then 250 μg every 2 hours with concomitant oxytocin therapy initiated after 24 hours. The results with this dose schedule were compared to the results obtained in a previous study with a higher dose schedule, an initial dose of 100 μg 15-ME-PGF_2α, followed in 1 hour by 250 μg then 500 μg every 2 hours. There was no significant difference in the mean abortion time and the incidence of side effects between the 2 dose schedules. The mean abortion time for patients with gestational ages of 16 weeks and less was the same with both dose schedules, however patients with gestational ages of 17 weeks and higher aborted somewhat faster with the higher dose schedule. It might therefore be advisable for patients with gestations of 17 weeks and higher to be treated with the higher dose schedule. In earlier gestations patients could be started on the lower schedule, and if abortion had not occurred within 15 hours the dose of 15-ME-PGF_2α could then be increased to 500 μg every 2 hours.     

Plasma concentrations of 9-deoxo-16,16-dimethyl-9-methylene-PGE2 in Rhesus monkeys after administration by various routes

A method is described for the estimation of 9-deoxo-16,16-dimethyl-9-methylene-PGE₂ by double antibody radioimmunoassay. Plasma samples obtained from animals treated with 9-methylene-16,16-dimethyl-PGE₂,1-adamantanamine salt were extracted with diethyl ether to recover the prostaglandin. The validation of sample preparation and assay procedure are presented. Rhesus females were treated by several routes of administration and the samples assayed for drug content. Maximum blood levels were probably reached 30 minutes following subcutaneous injection and within 30 seconds of an intravenous injection. Results of the acute intravenous injection indicate an initial half-life of approximately one minute in peripheral circulation. Continuous intravenous infusion at 3 increasing doses of this compound resulted in a stepwise increase in plasma drug concentrations. Vaginal administration of 9-methylene-16,16-dimethyl-PGE₂,1-adamantanamine salt in suppositories produced a dose dependent increase in plasma drug concentration. Higher plasma drug concentrations were produced when the prostaglandin was delivered in H-15 base suppositories than in E-76 base suppositories.     

Midtrimester abortion induced by a single intra-amniotic instillation of two dose schedules of 15(S)-15-methyl-prostaglandin F2α

Midtrimester abortion was successfully induced in a series of 20 patient by intra-amniotic instillation of 15(S)-15-methyl-prostaglandin F_2α with a mean abortion time of 17.78 hours. The patients in this study were divided into two groups, Groups I received on initial dose of 2.5 mg 15-ME-PGF_2α and aborted in a mean time of 16.26 hours. The patients in Group II received 3.0 mg 15-ME-PGF_2α and aborted in a mean time of 18.94 hours. There was no significant difference in the abortion time, occurrence of side effects or the initiation of uterine activity between Group I and Group II. Parous patients aborted somewhat faster than nulliparous patients but this difference was not significant. In this study 80% of the patients aborted in 24 hours or less, and the intra-amniotic instillation of 15-ME-PGF_2α was an effective abortifacient technique from the 15th to the 23rd week of gestation. The uterine response to intra-amniotic instillation of 15-ME-PGF_2α was characterized by the gradual appearance of low amplitude, high frequency contractions accompanied by a rise in baseline intrauterine tonus. Uterine activity developed gradually and peaked at 1:50 hours after intra-amniotic instillation of 15-ME-PGF_2α. In this small series 15-ME-PGF_2α administered via intra-amniotic instillation did not appear to have a distinct advantage over the naturally occurring PGF_2α administered by the same method for the induction of midtrimester abortion; a larger series is indicated to define the advantages of either technique.     

Extra-amniotic 15(S)-15 methyl PGF2α to induce abortion: A study of three administration schedules

Abortion was induced in 60 patients between 8 and 18 weeks gestation using 15(S)-15 methyl PGF₂α in one of three extra-amniotic administration schedules: 1.0 mg in viscous medium (Tylose), 1 mg in viscous medium (Hyskon) or 0.5 mg in non-viscous medium repeated at 12 hours. Eighty per cent of patients aborted within 24 hours in each group. The overall mean induction-abortion interval (± S.E.) was 17.6 ± 2.0: there was no significant difference between the three groups. Twenty patients treated with 1.0 mg in viscous medium had the catheter removed immediately following the prostaglandin injection and the success rate was not significantly altered.Gastro-intestinal side effects (vomiting in 50%, diarrhoea in 32.5%) were more frequent in the patients treated with the larger dose though the difference was not statistically significant. No significant haematological or biochemical changes were detected during the 24 hours following the start of treatment in 24 patients investigated. Thirty seven of the 60 patients (61.5%) aborted completely and did not require surgical evacuation, and none lost more than 500 ml of blood, nor required transfusion.It is concluded that abortion can be induced with a single extra-amniotic injection of 1 mg of 15(S)-15 methyl PGF₂α in viscous medium in a large percentage of patients but that the incidence of side effects is high.     

Single extra-amniotic injection of prostaglandin E2 in viscous gel to induce mid-trimester abortion.

In a preliminary study a single extra-amniotic injection of 1.5 mg of prostaglandin E-2 incorporated into an aqueous viscous gel was given to 24 patients aborted within 24 hours, and the mean induction-abortion interval (plus or minus S.E. of mean) was 13.5 plus or minus 1.5 hours. Vomiting occurred in seven patients, and transient severe uterine cramps, pallor, nausea, and shivering occurred in one patient immediately after injection. Complete abortion occurred in 20patients. A delay in the time taken to abort seemed to be associated with an immediate and rapid rise in uterine tone after the injection which required prompt analgesia; this probably reflected rapid decidual absorption and dissolution of the prostaglandins away from their site of action. The degree of distention of the catheter-retaining balloon did not influence abortion times.     

Prostaglandin analogues and uterotonic potency: A comparative study of seven compounds

The uterotonic potency of seven prostaglandin analogues has been investigated using the single intravenous injection technique and comparison of threshold uterine contractility achieved during continuous intravenous infusion. The degree and duration of uterine stimulation in response to graded doses of some of the analogues was also evaluated following intra-amniotic, oral and vaginal administration. 17-Phenyl substituted PGE₂ and PGF_2α are reported upon for the first time. Among the prostaglandin compounds tested, the free acid of 16,16-dimethyl PGE₂ not only is the most potent compound but it may also have great potential for clinical application as an easily administered vaginal abortifacient.     

Gas chromatographic — Mass spectrometric quantitation of 16,16-dimethyl-trans-Δ2-PGE1

Di-deuterated and di-tritiated 16,16-dimethyl-trans-Δ²-PGE₁ has been synthesized and used for development of a GC-MS method for quantitation of corresponding unlabelled drug in patient plasma. Although these carrier/internal standard molecules only contain 2 deuterium atoms the lower limit of detection at each injection is as low as about 40 pg.The maximum plasma levels of this drug following administration of vaginal suppositories used in clinical studies (1 mg 16,16-dimethyl-trans-Δ²-PGE₁ methyl ester in 0.8 g Witepsol S-52) were 100–350 pg/ml i.e. in the same order of magnitude as earlier seenf ro 16,16-dimethyl-PGE₂.     

Uterine stimulant action of some ω-chain modified (+)-11-deoxyprostaglandins

Rat uterine stimulant activity has been determined in vivo for a series of ( )-11-deoxyprostaglandins. The most active members of the series: 11-deoxy-15 methyl-PGE₁, 11-deoxy-16, 16-dimethyl-PGE₁ and its 1-alcohol were 2–3 times more potent than PGE₁. Gastrointestinal side effects assessed by the antagonism of morphine-induced constipation in the mouse, were generally relatively low with these compounds and consequently several members of the series had a more favourable relative selectivity than 16,16-dimethyl-PGE₂ methyl ester.     

Gas chromatographic — Mass spectrometric quantitation of 16,16-dimethyl-trans-Δ-PGE1

Di-deuterated and di-tritiated 16,16-dimethyl-trans-Δ²-PGE₁ has been synthesized and used for development of a GC-MS method for quantitation of corresponding unlabelled drug in patient plasma. Although these carrier/internal standard molecules only contain 2 deuterium atoms the lower limit of detection at each injection is as low as about 40 pg.The maximum plasma levels of this drug following administration of vaginal suppositories used in clinical studies (1 mg 16,16-dimethyl-trans-Δ²-PGE₁ methyl ester in 0.8 g Witepsol S-52) were 100–350 pg/ml i.e. in the same order of magnitude as earlier seenf ro 16,16-dimethyl-PGE₂.     

Synthesis and biological properties of 9-deoxo-16,16-dimethyl-9-methylene-PGE2.

The in vivo monkey uterine stimulating potency of 9-deoxy-16,16-dimethyl-9-methylene-PGE2 is similar to that of 16,16-dimethyl-PGE2 and approximately 15 times that of PGE2. Low doses of this compound stimulated uterine contractions when administered vaginally. Pregnancy was terminated prematurely following subcutaneous, intramuscular or vaginal suppository treatment. Estimates of potential for gastrointestinal side effects using the rat enteropooling assay and in vivo monkey effects indicate that diarrhea will be substantially reduced with retention of uterine stimulating potency.