Therapeutic uses of prostaglandins

Novel cyclooxygenase-catalyzed bioactive prostaglandin F2alpha from physiology to new principles in inflammation

Prostaglandin F2alpha (PGF2alpha), a foremost stable vasoactive cyclooxygenase (COX)-catalyzed prostaglandin, regulates a number of key physiological functions such as luteolysis, ovarian function, luteal maintenance of pregnancy, and parturition as a constitutive part of ongoing reproductive processes of the body. It has recently been implicated in the regulation of intricate pathophysiological processes, such as acute and chronic inflammation, cardiovascular and rheumatic diseases. Since the discovery of a second isoform of COXs, it has been shown that PGF2alpha can be formed in vivo from arachidonic acid through both isoforms of COXs, namely cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Being synthesized in various parts of the body, it metabolizes instantly to a number of rather inactive metabolites mainly in the lungs, liver, kidney, and efficiently excretes into the urine. 15-Keto-dihydro-PGF2alpha, a major stable metabolite of PGF2alpha that reflects in vivo PGF2alpha biosynthesis, is found in larger quantities than its parent compound in the circulation and urine in basal physiological conditions, with short-lived pulses during luteolysis, induced termination of pregnancy and parturition, and is increased in tissues and various body fluids during acute, sub-chronic, and severe chronic inflammation. Further, the close relationship of PGF2alpha with a number of risk factors for atherosclerosis indicates its major role in inflammation pathology. This review addresses multiple aspects of PGF2alpha in addition to its emerging role in physiology to inflammation.

Natural Prostaglandins for Induction of Labor and Preinduction Cervical Ripening

Prostaglandin (PG) E2 has superseded all other natural prostaglandins for induction of labor and pre-induction cervical ripening. This evolution and its rationale are briefly described. PGE2 has been administered intravenously, orally, vaginally, endocervically, and extra-amniotically for induction of labor. All of these, except the intravenous route, have also been explored for pre-induction cervical ripening. The distinction between formal induction and pre-induction is not always clearly made with many studies pursuing both goals at once. Nevertheless, the effectiveness of PGE2 to achieve ripening and induction is currently beyond doubt. In women with unfavorable induction prospects PGE2 results in lower rates of failed induction and higher rates of delivery within a reasonable interval than amniotomy and/or oxytocin. This also applies to women with prelabor rupture of the membranes, but the relative advantages of PGE2 over traditional methods are less clear for women with a favorable cervix. Vaginal administration of PGE2 has superseded virtually all other routes of PGE2 administration except the endocervical route, which tends to give variable results depending on spillage from the endocervical canal. Doses and formulations of vaginal PGE2 with various gels, tablets, pessaries and slow release inserts have varied widely and continue to do so. There is currently no evidence for the superiority of one PGE2 preparation over another.

[Morbidity of dilatation and evacuation in the second trimester: an analysis]

OBJECTIVE

To compare the rates of complications of dilatation and evacuation (D&E) in the second trimester of pregnancy.

STUDY DESIGN

Retrospective analysis of early complications after D&E in the second trimester (group A: 1988-1994) in comparison with D&E in the first trimester (group B: 1997) and with the induction of abortion by extra-amniotic application of prostaglandins in the second trimester of pregnancy (literature).

RESULTS

The overall complication rate of D&E was statistically significantly higher in the second than in the first trimester (p < 0.0001). The most frequent complication in both groups was a blood loss > 500 ml (p < 0.009). As with blood loss, there was a statistically significant increase in the incidence of postoperative bleeding (p < 0.001) and fever > 38 degrees C (p = 0.042) with rising gestational age, too. We registered similar rates for incomplete abortion, infection, cervical injury, uterine perforation and thrombosis.

CONCLUSION

Second-trimester pregnancy termination with D&E is associated with higher morbidity rates than in the first trimester. Overall, the rates of complications of D&E in our study were acceptable and comparable with the results of previous studies. Compared with the induction of abortion by extra-amniotic prostaglandins, D&E shows lower morbidity rates. In particular, the advantages of D&E are in the early second trimester.

Which factors influence the number of gemeprost pessaries used in inducing second-trimester abortions?

BACKGROUND

The course of second-trimester abortions with the intention to use gemeprost as the only abortifacient is described.

METHODS

The report is based on 278 consecutive second-trimester abortions, excluding missed abortions, during a 12-year period in a tertiary referral center. The women were treated with 1 mg gemeprost pessaries every fourth hour with a maximum of five applications during 24 h. If abortion had not occurred, a new treatment of gemeprost was prescribed after an interval of 12 h.

RESULTS

The median number of gemeprost pessaries used was 4 (range 1-16) and the mean number (+/-SD) 4.09 (+/-1.90). Abortion occurred within 24 h in 78% of the women and within 48 h in 96%. The efficiency of gemeprost was highly dependent on previous vaginal deliveries (p<0.001), with a mean number of applications of 4.63 (+/-2.04), 3.93 (+/-1.74), and 3.13 (+/-1.26) in those with none, one, and two or more previous vaginal deliveries, respectively. Previous spontaneous abortions were associated with a lower number of applications. Including previous vaginal deliveries and spontaneous abortions in a two-way analysis of variance (anova), only the number of spontaneous abortions was marginally significant (p=0.05). After excluding four patients with three or more spontaneous abortions from the analysis, the number of previous vaginal deliveries was significant (p=0.010) whereas that of spontaneous abortions became nonsignificant. Postprocedure complications were reported in 13% of the women.

CONCLUSION

The course of the abortions was dependent on previous vaginal deliveries and spontaneous abortions.

Pre-term cervical ripening and labor induction

OBJECTIVE

To evaluate retrospectively pre-term induction; with Prostaglandin (PG) E(2)-gel and i.v. oxtytocin, respectively.

METHODS

Fifty pre-term women with a gestational age between 28 + 0 and 36 + 6 and medical indications for labor induction were compared with the two next induced at term and post-term. The obstetric end points were numbers of PGE(2)-gel applications, failed inductions, instrumental delivery and heavy bleeding after partus (>1000 ml). The neonatal outcome was registered as operative delivery for fetal distress (ODFD) or Apgar score <7 at 5'.

RESULTS

The number of PGE(2)-gel applications did not differ. The duration of labor was shorter in the pre-term group (P = 0.043). A five-fold higher risk of heavy postpartum bleeding (>1000 ml) was noticed in the post-term group compared to the pre-term. The incidence of low Apgar scores were similar in the three groups.

CONCLUSIONS

Safe vaginal labor induction and delivery can be anticipated pre-term with PGE(2)-gel.

Human cervical ripening is associated with an increase in cervical inducible nitric oxide synthase expression

The mechanisms that ultimately regulate cervical ripening during parturition remain largely unknown. A possible role for nitric oxide (NO) has recently emerged; however, the expression of NO synthase (NOS) within the human cervix in the ripening process has not been investigated. The purpose of this study was to identify cell types in the human cervix that contain NOS isoforms and to examine changes in their expression during the ripening process and the nonpregnant state. Inducible NOS (iNOS) immunoreactivity was observed in the epithelial cells and stromal spindle cells in 17 of 20 biopsies from cervices obtained within 10 min postpartum, but in only 4 of 12 nonpregnant controls (p = 0.03). Endothelial NOS (eNOS) immunoreactivity was restricted to vascular endothelia in all sections, whereas neuronal NOS was not detectable. Inducible NOS activity in the postpartum group was 3.2 times that of the control group (p = 0.0005), whereas constitutive NOS activity remained unchanged in both groups (p = 0.222). Competitive reverse transcription-polymerase chain reaction revealed no differences in the expression of iNOS (p = 0.443) or eNOS mRNA (p = 0.409). The existence of iNOS in the human postpartum cervix suggests that increased production of NO, probably induced by cytokines, may be relevant to the process of natural cervical ripening in humans.

Investigation of the percutaneous penetration of prostaglandin E1 and its ethyl ester

The optimization of percutaneous delivery of PGE1 and its ethyl ester in alcoholic buffer solution through hairless mouse skin was investigated. A reversed-phase HPLC system with a photodiode array detector was used to differentiate the UV spectra of the penetration products. By comparison of the UV spectrum for each chromatographic peak, the conversion of PGE1 ethyl ester to PGE1 by enzymatic hydrolysis was found to be the predominant degradation pathway during the in vitro penetration. The quantification of ethyl ester was developed based on the same principle as that for PGE1. It was then applied to monitor the penetration of prostaglandins through hairless mouse skin from the vehicles containing various fractions of alcohol. Results demonstrated that the alkyl group promoted the penetration mainly as a result of enhancing the drug partitioning into the stratum corneum at its maximal thermodynamic activity. The alcohol fraction around 20% seemed to be optimal for the percutaneous delivery of the ethyl ester. The use of collagen gel to carry PGE1 ethyl ester for percutaneous application was included for comparison. The effect of adding alcohol in the collagen gel on the penetration of PGE1 ethyl ester was found to be slightly lower than that from the same vehicle without collagen.

Controlled comparison of induction versus expectant care for prelabor rupture of the membranes at term

This randomized clinical trial compared oxytocin induction of labor with expectant care for 48 hours after prelabor rupture of the membranes at term. Women at term with prelabor rupture of the membranes for at least 8 hours were assigned at random to induction with oxytocin or to expectant management for 48 hours followed by induction if necessary. Of 168 eligible women, 123 (73%) agreed to participate. More women in the induction group (23%) than in the expectant group (10%) had operative delivery, either cesarean section or instrumental vaginal delivery. In the induction group 41% received analgesia versus 24% in the expectant group (p < 0.005). There was no difference in the rate of maternal and neonatal infection between groups and sepsis was not observed. The active policy of oxytocin induction exposed the mother to a higher risk of operative delivery and a less comfortable labor than the 48 hours expectant care option.

Controversies: the mature breech should be delivered by elective cesarean section

The fetal hazards of vaginal breech delivery have been recognised for centuries. In recent years the increased safety of Cesarean delivery has prompted a steady rise in its use for the delivery of the term breech fetus. In many maternity units more than 90% of breech babies are delivered in this way. In contrast some obstetricians argue that with appropriate selection criteria, safe, selective, vaginal breech delivery is possible. This argument is not supported by population studies, which indicate that perinatal mortality and morbidity rates associated with attempts at vaginal breech delivery are between 1-2%.

Randomized comparison of the effects of endocervical and vaginal prostaglandin E2 gel in women with various degrees of cervical ripeness. Dutch Collaborative Prostaglandin Trialists' Group

OBJECTIVE

The trail was conducted to obtain an unbiased comparison of the relative merits of endocervical and vaginal prostaglandin E2 gel in a weighted case mix of parous and nulliparous women with favorable and unfavorable cervical features.

STUDY DESIGN

Multicenter randomized trial with 285 participants, (three exclusions) was performed with sealed envelopes stratified for parity and Bishop score.

RESULTS

Outcomes of labor and delivery were clearly related to the cervical score at trial entry, especially in nulliparous women. Endocervical prostaglandin E2 had a more marked effect on cervical ripeness than did vaginal prostaglandin E2, but this did not result in any differences in more substantive outcomes. Frequencies of delivery within 12 (50%) and 24 hours (77.7%), cesarean section (7.3%), instrumental vaginal delivery (11.7%), and poor infant outcomes were similar with both preparations.

CONCLUSION

Because differences in effectiveness between endocervical and vaginal prostaglandin E2 in triacetin gel are marginal, preferences of women and clinicians can determine the choice between them.