Metabolism and pharmacokinetic studies of misoprostol

Development and validation of a stability-indicating method, structural elucidation of new degradation products from misoprostol by LC-MS time-of-flight, and an ex vivo study of vaginal permeation

Misoprostol (MSP) is commonly prescribed in obstetrics and gynecology clinical practice for labor induction, cervical ripening, first-trimester pregnancy termination, and the treatment of postpartum hemorrhage. Furthermore, there is a lack of comprehensive discussion evaluating how different commercially available formulations influence the overall efficacy of MSP, even though reports indicate issues with the quality of these formulations, particularly regarding stability and vaginal absorption processes. This study investigates the stability of MSP under acidic conditions and its in vitro permeation using swine vaginal mucosa. A forced degradation study was conducted using 0.2 M HCl, and a high-efficiency LC method was developed. Three degradation products were identified and characterized using electrospray ionization-high-resolution quadrupole-time-of-flight-MS, with respective m/z values of 391.2508, 405.2705, and 387.2259, respectively. These results suggest that the degradation mechanism involves dehydration of the β-hydroxy ketone moiety, followed by isomerization to its most resonance-stable form and de-esterification. Finally, the in vitro permeation study revealed that the esterified form of MSP was unable to permeate the mucosa and required prior degradation for any component to be detected in the receptor fluid.

Pharmacokinetics of Vaginal vs Buccal Misoprostol for Labor Induction at Term

The IMPROVE study (NCT02408315) compared the efficacy and safety of vaginal and buccal administration of misoprostol for full‐term, uncomplicated labor induction. This report compares the pharmacokinetics of misoprostol between vaginal and buccal routes. Women greater than or equal to 14 years of age undergoing induction of labor greater than or equal to 37 weeks gestation without significant complications were randomized to vaginal or buccal misoprostol 25 μg followed by 50 μg doses every 4 h. Misoprostol acid concentrations were determined using liquid chromatography‐tandem mass spectrometry for the first 8 h in a subgroup of participants. A population pharmacokinetic model was developed using NONMEM. Plasma concentrations (n = 469) from 47 women were fit to a one‐compartment nonlinear clearance model. The absorption rate constant (k_a) was dependent on both route and dose of administration: buccal 25 μg 0.724 (95% confidence interval, 0.54–0.92) h⁻¹; 50 μg 0.531 (0.37–0.63) h⁻¹; vaginal 25 μg 0.507 (0. 2–1. 4) h⁻¹; and 50 μg 0.246 (0.103–0.453) h⁻¹. Relative bioavailability for vaginal compared to buccal route was 2.4 (1.63–4.77). There was no effect of body mass index or age on apparent clearance 705 (431–1099) L/h or apparent volume of distribution 632 (343–1008) L. The area under the concentration–time curve to 4 h following the first 25 μg dose of misoprostol was 16.5 (15.4–17.5) pg h/ml for buccal and 34.3 (32.5–36.1) pg h/ml for vaginal administration. The rate of buccal absorption was two times faster than that of vaginal, whereas bioavailability of vaginal administration was 2.4 times higher than that of buccal. Decreased time to delivery observed with vaginal dosing may be due to higher exposure to misoprostol acid compared to buccal.

Pharmacokinetics and Bioequivalence of Misoprostol Tablets: An Open-Label, Randomized, Single-dose, Crossover Study With Healthy Chinese Volunteers

Misoprostol is a synthetic prostaglandin E1 derivative that has been used to treat duodenal and gastric ulcers, and to prevent ulcers caused by nonsteroidal anti-inflammatory drugs in many countries. Misoprostol can also be used for medical abortion. This study aimed to investigate the pharmacokinetic profiles of misoprostol tablets (test product) by comparing them with Cytotec (200 μg) (reference product). To assess the bioequivalence between test and reference products, a two-sequence, two-period crossover study was conducted with 48 healthy Chinese subjects enrolled under fasting conditions. A validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was used to determine the concentration of misoprostol acid in plasma. A mixed model analysis of variance was used to calculate the bioequivalence of pharmacokinetic (PK) parameters. The point estimate of geometric mean ratios with 90% confidence intervals for the maximum observed concentration (C_max ) and the area under the concentration-time curve (AUC_0-t ) for misoprostol acid in reference and test products were 107.8% and 106.5%, respectively (range 80%-125%). Additionally, none of the secondary PK parameters presented significant differences. No severe or more than moderate adverse events were detected in the 48 subjects. However, one subject discontinued the treatment due to drug-related gastrointestinal reactions. All adverse events were mild with rates of 19.2% and 22.9% after the administration test and reference products, respectively. Overall, the bioequivalence between the two misoprostol products was demonstrated in fasting conditions, and all subjects tolerated both treatments.

Second trimester medical abortion in a primigravida with lupus nephritis and rapidly progressive renal failure: challenges and outcome

In the second trimester, medical abortion is preferred as it is less invasive, and the surgical method carries more risk. There is a paucity of published literature on medical abortion in women with renal failure requiring haemodialysis. We came across a woman who presented with rapidly progressive renal failure at 18 weeks of gestation and required therapeutic abortion. We are reporting the challenges, outcomes, and precautions to be taken while performing a medical abortion in such a case.

Personalized Mapping of Drug Metabolism by the Human Gut Microbiome

The human gut microbiome harbors hundreds of bacterial species with diverse biochemical capabilities. Dozens of drugs have been shown to be metabolized by single isolates from the gut microbiome, but the extent of this phenomenon is rarely explored in the context of microbial communities. Here, we develop a quantitative experimental framework for mapping the ability of the human gut microbiome to metabolize small molecule drugs: Microbiome-Derived Metabolism (MDM)-Screen. Included are a batch culturing system for sustained growth of subject-specific gut microbial communities, an ex vivo drug metabolism screen, and targeted and untargeted functional metagenomic screens to identify microbiome-encoded genes responsible for specific metabolic events. Our framework identifies novel drug-microbiome interactions that vary between individuals and demonstrates how the gut microbiome might be used in drug development and personalized medicine.

A Relative Bioavailability Study of Two Misoprostol Formulations Following a Single Oral or Sublingual Administration

Introduction

Misoprostol (Cytotec) was primarily made for treating gastric ulcers. However today it is mostly used for abortion, treating postpartum hemorrhage, and for induction of labor. The tablet contains 200 µg of misoprostol, yet the dosages used for induction of labor are much smaller (25–50 µg), leading to uncertainty of dosage in daily use.

Aim

To evaluate and compare the relative bioavailability of two misoprostol products (Angusta 25 µg and Cytotec 200 µg tablets) administered orally or sublingually given in a daily clinical setting to women admitted for induction of labor at term.

Methods

Women carrying a live, singleton fetus in a cephalic position and with a gestational age between 259 and 296 days were included. Blood samples were collected at 0, 5, 10, 20, 30, 40, 50, 75, 100, 120, 180, and 240 minutes. A serum analytical assay was performed and pharmacokinetic parameters were calculated. Patients were assigned to one of three groups.

Results

A total of 72 patients were included. No significant differences demographic characteristics were found. The ratios for AUC, AUC (_0−t), and C_max were similar in all three groups, but CI-values were outside the required 80–125%. Sublingual administration yielded a 20–30% higher bioavailability and a 50% higher C_max than compared to the oral route.

Conclusion

The relative bioavailability between Angusta and Cytotec could not be confirmed as being equal at the 25 µg or 50 µg level because the 90% CI-values when comparing the ratios for AUC, AUC_(0−t), and C_max were wider than accepted. The reason for this could be the real-life, non-standardized circumstances in which the study was conducted. Sublingual administration seems to have higher bioavailability than oral administration. More studies are needed to ascertain an optimal dosage regime balancing both safety and efficacy for mother and child.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT02516631.

Effect of oral misoprostol, alone or in combination with aglepristone, on mid-term pregnancy termination in cats

OBJECTIVES

This study aimed to determine the efficacy and safety of oral misoprostol (MIS) administration in the induction of mid-term pregnancy termination in cats.

METHODS

Twenty-eight cats that were pregnant for 30-40 days were allocated to four groups. The aglepristone (AGL) group (n = 7) received 10 mg/kg SC aglepristone q24h for two consecutive days. In the AGL+MIS group (n = 7), AGL (as administered in the AGL group) and MIS (200 µg/cat PO q12h until the start of abortion) were administered. The MIS200 (n = 7) and MIS400 groups (n = 7) received MIS (200 or 400 µg/cat misoprostol, respectively) alone PO q12h until the start of abortion. Blood samples were collected at the start of treatment (d0), 4 days after the start of treatment (d4) and on the day of complete abortion/end of administration (dA/d7).

RESULTS

The efficacy of the treatment was 71.4% in the AGL group, 100% in the AGL+MIS group, 0% in MIS200 group and 57.4% in MIS400 group (P = 0.004). No significance was found in relation to the interval from treatment to the start/end of abortion and the duration of abortion in all groups. The most observed side effect was vomiting in both groups administered MIS, particularly in the MIS400 group (56.7%). Progesterone (P4) concentrations were reduced during the abortion, but not to basal levels, in all groups. P4 concentrations were significantly lower at dA/d7 in the MIS400 group compared with the AGL and AGL+MIS groups (P = 0.002).

CONCLUSIONS AND RELEVANCE

The results obtained from this study showed that low doses of MIS do not induce abortions in cats but increase the effect of AGL. Although higher doses could terminate pregnancies, this also causes intense unwanted side effects. Therefore, the use of MIS alone as an abortifacient in cats is not recommended. For mid-term pregnancy termination in cats, the combination of misoprostol and aglepristone provides a more effective abortifacient than using either of them alone.

Misoprostol-induced fever and genetic polymorphisms in drug transporters SLCO1B1 and ABCC4 in women of Latin American and European ancestry

AIM

Misoprostol, a prostaglandin analogue used for the treatment of postpartum hemorrhage and termination of pregnancy, can cause high fevers. Genetic susceptibility may play a role in misoprostol-induced fever.

SUBJECTS & METHODS

Body temperature of women treated with misoprostol for termination of pregnancy in the UK (n = 107) and for postpartum hemorrhage in Ecuador (n = 50) was measured. Genotyping for 33 single nucleotide polymorphisms in 15 candidate genes was performed. Additionally, we investigated the transport of radiolabeled misoprostol acid across biological membranes in vitro.

RESULTS

The ABCC4 single nucleotide polymorphism rs11568658 was associated with misoprostol-induced fever. Misoprostol acid was transported across a blood-brain barrier model by MRP4 and SLCO1B1.

CONCLUSION

Genetic variability in ABCC4 may contribute to misoprostol-induced fever in pregnant women. Original submitted 21 January 2015; Revision submitted 24 April 2015.

Claims of misoprostol use based on blood sampling should be viewed with skepticism

Efforts to prosecute women for induced abortion have included allegations that misoprostol was found in body fluids. These claims, however, are questionable owing to the timing of specimen collection for accurate results, the scarcity and expense of validated assays, and the onerous lab procedures required to determine the presence of the substance. Adequate scrutiny should be applied each time such a claim is made.

Oral versus vaginal misoprostol for induction of labor in Enugu, Nigeria: a randomized controlled trial

OBJECTIVE

The study aimed at comparing the effectiveness and maternal satisfaction of oral misoprostol with vaginal misoprostol for induction of labor at term.

MATERIALS AND METHODS

A randomized controlled trial of 140 term pregnant women at the University of Nigeria Teaching Hospital Enugu, Nigeria, was conducted from April 2011 to May 2012. The women were equally randomized into two groups (A and B) to receive oral and vaginal misoprostol, respectively.

RESULTS

The vaginal route reduced the mean induction-vaginal delivery interval by four-and-half hours (20.7 ± 12.1 vs. 16.2 ± 10.4; mean difference: 4.50, 95% CI 0.63-0.82; p = 0.02). Furthermore, the mean dose of misoprostol required to achieve induction of labor and the mean duration of oxytocin augmentation when indicated were significantly less in the vaginal group than in the oral group (2.5 ± 1.3 vs. 2.0 ± 1.1; mean difference: 0.50, 95% CI 0.10-0.90; p = 0.02 and 4.6 ± 3.2 vs. 3.4 ± 3.1; mean difference: 1.20, 95% CI 0.15-0.23; p = 0.03 respectively). However, neonatal complications and maternal satisfaction were similar between the two groups.

CONCLUSION

Both routes of administration are effective in the induction of labor at term and have comparable maternal satisfaction. However, the vaginal route has the added advantage of shorter induction-delivery interval among others, and thus should be highly considered when induction of labor is indicated at term.

Acute Hemolytic Anemia With Acanthocytosis Associated With High-Dose Misoprostol for Medical Abortion

We report a case of acute hemolytic anemia in a 21-year-old Nigerian woman after high-dose misoprostol (4 mg), used for medical abortion. The major causes of inherited or immune hemolytic anemia were excluded. The patient's peripheral blood smear showed acanthocytes and anisopoikilocytosis, which progressively disappeared in the days postingestion. We evaluated RBC features, and we observed reduced RBC Na+ and K+ content and abnormalities in membrane cation transport pathways and in Ca2+ activated K+ channel (Gardos channel), suggesting possible direct effects of misoprostol on RBCs. Although further studies need to be carried out, the present case suggests that high-dose misoprostol, a prostaglandin E1 analogue, severely affects RBC features and causes an acquired acute hemolytic anemia, which is self-limited when misoprostol is withdrawn.

Determination of misoprostol acid in human plasma by liquid chromatography coupled to tandem mass spectrometry

A rapid and sensitive liquid chromatographic/tandem mass spectrometric method for determination of misoprostol acid, the active metabolite of misoprostol, was developed and validated. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a C(18) column. An API 4000 tandem mass spectrometer equipped with Turbo IonSpray ionization source was used as detector and was operated in the negative ion mode. Multiple reaction monitoring using the precursor to product ion combinations of m/z 367-249 and 296-269 was performed to quantify misoprostol acid and the internal standard hydrochlorothiazide, respectively. The method was linear in the concentration range of 10.0-3000 pg mL(-1) using 200 microL plasma. The lower limit of quantification was 10.0 pg mL(-1). The intra- and inter-day relative standard deviation over the entire concentration range was less than 8.3%. Accuracy determined at three concentrations (25.0, 200 and 2700 pg mL(-1) for misoprostol acid) ranged from -0.5 to 1.2% in terms of relative error. Each plasma sample was chromatographed within 3.5 min. The method was successfully used in a pharmacokinetic study of misoprostol in human plasma after an oral administration of 0.6 mg misoprostol.

Determination of misoprostol free acid in human breast milk and serum by gas chromatography/negative ion chemical ionization tandem mass spectrometry

To study an expected transition of misoprostol from human blood into breast milk, a novel method for the determination of its active metabolite misoprostol acid (MPA) was developed. MPA was determined in serum and breast milk samples by an isotope dilution assay using gas chromatography/negative ion chemical ionization tandem mass spectrometry (GC/NICI-MS/MS). After addition of (15S)-15-methylprostaglandin E(2) (15-methyl-PGE(2)) as an internal standard, MPA was extracted from both matrices using a reversed-phase cartridge. The prostanoids were derivatized with O-2,3,4,5,6-pentafluorobenzylhydroxylamine hydrochloride (PFBHA) and 2,3,4,5,6-pentafluorobenzyl bromide (PFBB) to the pentafluorobenzyl oxime (PFBO)-pentafluorobenzyl ester (PFB) derivatives. The sample was subjected to thin-layer chromatography with ethyl acetate-hexane (1 : 1 (v/v)) as the developing solvent. The corresponding zone was extracted. After derivatization to the trimethylsilyl ether, MPA was determined by GC/NICI-MS/MS using the [molecule (M) - pentafluorobenzyl (PFB)](-) ([P](-)) ions as precursor in the negative ion chemical ionization mode. The product ions used for quantification were [P - 2TMSOH - C(6)F(5)CH(2)OH](-) (MPA) and [P - 2TMSOH - C(6)F(5)CH(2)OH - CO(2)](-)(15-methyl-PGE(2)), respectively. The limit of quantification for MPA was approximately 1 pg ml(-1) in breast milk and serum samples. The correlation coefficients of the calibration curves for MPA were r > 0.997 in the 0.5-2000 pg ml(-1) range for both tested matrices.

Pharmacokinetics and pharmacodynamics of antiulcer agents in llama

Plasma concentration time curves following intravenous (i.v.) administration of 1.5 mg/kg of ranitidine, 0.2 mg/kg, 0.4 mg/kg and 0.8 mg/kg of omeprazole, respectively, were analysed in six llamas. Plasma profiles after i.v. administration of both drugs showed plasma concentrations declining in a biexponential manner with a rapid distribution phase. Pharmacokinetics parameters after ranitidine administration to six llamas showed a mean elimination half-life of 1.53 +/- 0.26 h. The mean volume of distribution (Vdss) in llamas was 1.77 +/- 0.31 L/kg, and mean body clearance in llamas was 0.778 +/- 0.109 L/kg/h. Ranitidine produced only a small transitory (<1 h) decline in acid production when administered i.v. at a dose of 1.5 mg/kg. Omeprazole showed dose-dependent nonlinear pharmacokinetics. The mean half-life of 0.2 mg/kg i.v. omeprazole was shorter than that of 0.4 and 0.8 mg/kg i.v. omeprazole, i.e. 0.61, 0.72 and 1.07 h, respectively. The area under the curve (AUC) and mean residence time (MRT) increased with increasing dose, while clearance decreased as dose increased. The decline in acid production following 0.2 mg/kg i.v. omeprazole was highly variable and did not produce a clinically useful suppression of third compartment acid production. In contrast, both 0.4 mg/kg and 0.8 mg/kg omeprazole i.v. administration significantly reduced third compartment acid production. The reduction in acid production following 0.8 mg/kg omeprazole was not significantly greater than the reduction observed following 0.4 mg/kg dosage. Misoprostol (10 microg/kg) was administered i.v. in an absolute alcohol solution. Two animals collapsed following drug administration. While the side-effects could have been produced by either misoprostol or the alcohol vehicle, the clinical changes were more consistent with an adverse drug reaction. Unfortunately, the limitation of UV detection did not provide the sensitivity needed to quantify the amount of misoprostol in llama plasma, and the pharmacokinetics could not be evaluated.

Misoprostol in labor induction

The efficacy of a new dosing regimen of misoprostol, a recently introduced labor-inducing agent, was studied. Fifty-eight patients received 50 microg of misoprostol intravaginally and the dose was repeated every 3 hours until uterine contractions begin. Those who had an adequate contraction pattern, defined as three contractions in 10 minutes, were not given the repeat dose. Oxytocin augmentation, but not further misoprostol doses, was used in patients with an inadequate contraction pattern. The maximum total daily dose was 200 microg. The patients had the mean age of 28.9 +/- 5.4, the mean gestational age of 211.8 +/- 46.6 days, the mean gravidity of 2.5 +/- 1.2, the mean parity of 0.9 +/- 0.9 and the mean initial Bishop score of 1.6 +/- 1.8. The mean required dose of misoprostol was 120.5 +/- 54.7 microg and 10 of 58 patients required oxytocin augmentation. The mean induction of labor to delivery time was 701.5 +/- 404.0 minutes. When 3 cases who gave birth with caesarean section were excluded, the interval was 708.4 +/- 407.2 minutes. The mean 5th minute Apgar score of the newborns was 8.2 +/- 2.5. Two patients developed tachysystole after the second dose of misoprostol and were managed with vaginal irrigation and O2 supplementation successfully. Slight nausea and vomiting in 2 patients were the other adverse reactions. Our findings revealed that, 50 microg intravaginal misoprostol, combined with oxytocin augmentation when necessary, appears to be an effective and safe method of labor induction.

Misoprostol therapeutics revisited

Misoprostol, a prostaglandin E1 analog, is a racemate of four stereoisomers. On administration it rapidly de-esterifies to its active form, misoprostolic acid. Misoprostolic acid is 85% albumin bound and has a half-life of approximately 30 minutes. It is excreted in urine as inactive metabolites. No significant drug interactions have been reported. Besides its gastrointestinal protective and uterotonic activities, misoprostol regulates various immunologic cascades. It inhibits platelet-activating factor and leukocyte adherence, and modulates adhesion molecule expression. It protects against gut irradiation injury, experimental gastric cancer, enteropathy, and constipation. It improves nutrient absorption in cystic fibrosis. Misoprostol has utility in acetaminophen and ethanol hepatotoxicity, hepatitis, and fibrosis. It is effective in asthmatics and aspirin-sensitive asthmatic and allergic patients. It lowers cholesterol and severity of peripheral vascular diseases, prolongs survival of cardiac and kidney transplantation, synergizes cyclosporine, and protects against cyclosporine-induced renal damage. It works against drug-induced renal damage, interstitial cystitis, lupus nephritis, and hepatorenal syndrome. It is useful in periodontal disease and dental repair. Misoprostol enhances glycosoaminoglycan synthesis in cartilage after injury. It prevents ultraviolet-induced cataracts and reduces intraocular pressure in glaucoma and ocular hypertension. It synergizes antiinflammatory and analgesic effects of diclofenac or colchicine and has been administered to treat trigeminal neuralgic pain. It reduces chemotherapy-induced hair loss and recovery time from burn injury, and is effective in treating sepsis, multiple sclerosis, and pancreatitis.

A comparison of differing dosing regimens of vaginally administered misoprostol for preinduction cervical ripening and labor induction

OBJECTIVE

Our purpose was to compare two dosing regimens of vaginally administered misoprostol for preinduction cervical ripening and induction of labor.

STUDY DESIGN

Five hundred twenty-two patients with indications for induction of labor and unfavorable cervices were randomly assigned to one of two dosing regimens of vaginally administered misoprostol. Twenty-five microgram tablets of misoprostol were placed in the posterior vaginal fornix either every 3 hours to a maximum of eight doses or every 6 hours to a maximum of four doses. The maximal period of cervical ripening was 24 hours regardless of the number of misoprostol doses administered. Medication was not given after either spontaneous rupture of membranes or the beginning of active labor.

RESULTS

Among 522 patients enrolled, 261 were randomized to receive misoprostol every 3 hours and 261 to receive misoprostol every 6 hours. The average interval from start of induction to vaginal delivery was shorter in the 3-hour dosing group (1311.74 +/- 785.14 minutes) than in the 6-hour dosing group (1476.96 +/- 805.30 minutes) (p < 0.05). Oxytocin augmentation of labor occurred more commonly in the 6-hour dosing group (51.4%) than in the 3-hour dosing group (41.8%) (p < 0.05) [corrected]. There were no significant differences between routes of delivery. Overall, 108 patients (20.8%) were delivered by cesarean section. There was a slightly higher prevalence of tachysystole (six or more uterine contractions in a 10-minute window for two consecutive 10-minute periods) in the 3-hour group (14.6%) than in the 6-hour group (11.2%), but this difference was not statistically different. There were no significant differences in the frequency of uterine hyperstimulation or hypertonus. There was no significant difference between groups in the frequency of abnormal fetal heart rate tracings, meconium passage, 1- or 5-minute Apgar scores < 7, neonatal resuscitations, or admissions to the neonatal intensive care unit.

CONCLUSIONS

Vaginally administered misoprostol is an effective agent for cervical ripening and induction of labor. Patients with the 6-hour dosing schedule had longer intervals to delivery, more frequently required oxytocin augmentation, and had more failed inductions than did patients with 3-hour dosing. Further investigation to characterize the safety of misoprostol is needed.

Effects of misoprostol on circulating HDL-cholesterol, total cholesterol, triglycerides and their relationship with hepatic microsomal function

The effects of misoprostol (cytotec, SC29333) on circulating lipoproteins and liver microsomal enzyme activity were studied. Misoprostol increased serum levels of high density lipoprotein-cholesterol and decreased total cholesterol and triglycerides. The high density lipoprotein-cholesterol/total cholesterol ratio increased by 54.8%. In parallel, misoprostol significantly altered enzyme hepatic activity. Liver microsomal cytochromes P450 and b5 were significantly increased in correlation with enhanced liver aminopyrine N-demethylase and antipyrine hydroxylase activities, suggesting a liver induction effect of misoprostol. Other observations such as increased liver weight and glycogen and increased plasma albumin and glucose in rats receiving misoprostol support this evidence.

Chronic effects of misoprostol in combination with the NSAID, diclofenac, on gastrointestinal tract of pigs. Relation to diarrheagenic activity, leukocyte infiltration, and mucosal leukotrienes

To determine the mode of protective effects of misoprostol against the chronic gastrointestinal ulceration from the NSAID, diclofenac, studies were undertaken in domestic pigs, a model of human gastrointestinal ulceration, to determine (1) the effects of repeated daily dosing for 10 days of diclofenac 5 mg/kg/day twice a day (as Voltaren tablets) on the gastrointestinal morphology, 59fe-red blood loss, mucosal myeloperoxidase (MPO) activity (as an indicator of leukocyte infiltration), and mucosal leukotrienes (LTS); and (2) the mucosal protective effects of 10-40 micrograms/kg/day misoprostol twice a day (as Cytotec tablets) given with diclofenac 5 mg/kg/day twice a day compared with diclofenac 5 mg/kg/day alone and aspirin 150 mg/kg/twice a day (USP tablets) as a standard. These effects were compared with the dose range for potential diarrheagenic effects of misoprostol (determined by fecal analysis of NA+, K+, CL-, CA2+, H2O, and phenol red transit) given alone or with diclofenac to determine if this could be discriminated from antiulcer effects of misoprostol. Plasma and gastric mucosal concentrations of the drugs were determined to establish if misoprostol affects diclofenac absorption/elimination, and vice versa. The results showed that: (1) diclofenac produced gastric mucosal damage without any prior or concurrent bleeding from the gastrointestinal tract, although aspirin significantly increased blood loss; (2) misoprostol produced a dose-related reduction in diclofenac-induced mucosal damage of the upper gastrointestinal tract; (3) no significant increase in mucosal MPO occurred with diclofenac despite mucosal damage being evident, (4) mucosal LTS were unaffected by the drug treatments; (5) plasma, gastric and intestinal concentrations of diclofenac were not affected by misoprostol, while conversely plasma misoprostol concentrations were not influenced by the diclofenac treatment; (6) no significant effects on fecal water, electrolyte, or phenol red transit times were observed with an of the drug-treatments; and (7) mild diarrhea observed as "loose bowel motions" was only observed in most pigs receiving the misoprostol treatments during fasting on days 9-10. Thus, misoprostol protects against chronic lesions/ulcers in the upper gastrointestinal tract from diclofenac without: (1) signs of diarrhea becoming evident (the latter occurring when there is reduced food intake), (2) generalized leukocyte infiltration or effects on mucosal LTs, or (3) any reduction in bioavailability of diclofenac.

Disposition of misoprostol and its active metabolite in patients with normal and impaired renal function

The disposition of misoprostol acid, the active metabolite of misoprostol, was studied in 48 subjects with various degrees of renal function after administration of a single 400 microgram oral dose of misoprostol. Subjects were assigned to one of four treatment groups: group 1, normal renal function with creatinine clearance (CLCR) 80-140 mL/min/1.73 m2; group 2, mild renal impairment with CLCR 50-79 mL/min/1.73 m2; group 3, moderate renal impairment with CLCR 20-49 mL/min/1.73 m2 or group 4, end stage renal disease (ESRD) patients maintained on hemodialysis. The maximum plasma concentration (Cmax) and time to reach Cmax (tmax) for misoprostol acid tended to be larger in group 4 subjects; however, it failed to reach statistical significance. Although not statistically significant, in group 4 subjects the terminal half-life (t1/2) of misoprostol acid was almost twice as large (1.27 +/- 0.77 h) as in groups 1, 2, and 3 (0.70 +/- 0.72, 0.72 +/- 0.67, and 0.73 +/- 0.45 h, respectively). Misoprostol acid's total area under the plasma concentration curve (AUC0 infinity) was larger in group 4 subjects (1173.5 +/- 487.4 pg.h/mL) as compared with groups 1, 2, and 3 (421.4 +/- 263.1, 418.9 +/- 114.5, and 377.0 +/- 145.2 pg.h/mL, respectively; P < .05). The apparent total body clearance (CL) of misoprostol acid was statistically significantly smaller in group 4 subjects (0.094 +/- 0.044 L/kg/min) as compared only with group 3 subjects (0.284 +/- 0.102 L/kg/min). The dose of misoprostol may need to be reduced in ESRD patients on prolonged hemodialysis to prevent unnecessary high plasma levels of misoprostol acid and to avoid possible dose-related adverse effects.

The effect of misoprostol on aspirin-induced gastroduodenal lesions in dogs

Misoprostol, a synthetic prostaglandin E1 analog, is effective in treating and preventing nonsteroidal antiinflammatory drug (NSAID)--induced gastrointestinal lesions in humans. The effectiveness of misoprostol in preventing aspirin-induced gastroduodenal injury was studied in 3 groups of 6 adult mixed breed dogs. Group I received 3 micrograms/kg misoprostol PO tid. Group II received 3 micrograms/kg misoprostol PO tid and 35 mg/kg aspirin PO tid. Group III received 35 mg/kg aspirin PO tid. Endoscopy was performed on days 0, 5, 14, and 30. Five regions of the upper gastrointestinal tract were qualitatively scored from 1 to 12 based on the presence of submucosal hemorrhage, erosion, or ulceration, with ulceration receiving a higher numerical score than submucosal hemorrhage. A total score was assigned based on the sum of the scores from all regions. Comparisons among groups on each day were performed using the Kruskal-Wallis test. Differences within a group among different time periods were determined using appropriate multiple comparisons. Significant difference in mean gastroduodenal lesion score was found among all groups at 5, 14, and 30 days. Mean total score on days 5, 14, and 30 were as follows: group I, 5.0, 5.2, 9.0; group II, 12.0, 12.7, 16.2; and group III, 26.0, 23.8, 21.5, respectively. Significant differences within a group among different time periods were found from days 0 to 5 in groups I and II, and from days 14 to 30 in group I. It was concluded that misoprostol effectively decreased endoscopically detectable mucosal lesions in dogs given aspirin.

Prostaglandins and inhibitors of arachidonate metabolism suppress experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is an autoimmune inflammatory disease of the central nervous system (CNS). It is an animal model of post-infectious encephalomyelitis and multiple sclerosis (MS). Acute EAE is mediated by macrophages and by T helper 1 (Th1) lymphocytes directed against brain antigens. Inflammation in EAE could potentially be modified by prostaglandins (PG) secreted by blood monocytes (Mo) and brain glial cells. PGE elevates cAMP, which inhibits Mo function and selectively blocks secretion of cytokines by Th1 cells. In the present study, we found that a long-acting PGE1 analogue (LAPGE) inhibited clinical and histological EAE. Indomethacin (INDO) also suppressed active EAE. The combination of INDO plus LAPGE inhibited disease further, possibly by allowing LAPGE to function unopposed by immunostimulatory PG. EAE was suppressed when these agents were administered from the time of immunization or from the onset of clinical disease. The combination of INDO plus LAPGE also inhibited delayed-type hypersensitivity (DTH) reactions to myelin basic protein (MBP), and diminished in vitro lymphocyte responses to mitogens and MBP. PGE analogues and modifiers of arachidonate metabolism block autoimmune responses to brain antigens in vitro and in vivo, and may ameliorate inflammatory and autoimmune diseases of the brain and other organs.

Influence of misoprostol, a synthetic prostaglandin E1 analog, on the healing of colonic anastomoses in rats

PURPOSE

This study was designed to examine the influence of misoprostol, a synthetic prostaglandin E1 analog, on the healing of colonic anastomoses in rats, with particular regard to changes in collagen levels at the site of the anastomoses and their histopathologic aspects.

METHODS

Sixty rats were submitted to resection and anastomosis of the colon, and divided at random into two groups. The test group received misoprostol intragastrically (200 micrograms/kg body weight), twice daily, from the day of operation until sacrifice. Controls received 0.9 percent NaCl. The animals were sacrificed on the third, seventh, or fourteenth postoperative day, and the results of the histopathologic analyses and hydroxyproline concentrations were compared.

RESULTS

Our results show that misoprostol administration increased the hydroxyproline concentration on the fourteenth postoperative day without interfering in the inflammatory response (P < 0.05).

CONCLUSION

Misoprostol interferes with the balance between the synthesis and degradation of collagen, resulting in an elevation of collagen levels by the fourteenth postoperative day without influencing the inflammatory response.

Effect of salicylic acid on the plasma protein binding and pharmacokinetics of misoprostol acid

The in vitro serum protein binding and erythrocyte uptake of [3H]misoprostol acid ([3H]MPA; SC-30695), an active metabolite of the prostaglandin E1 (PGE1) analogue misoprostol, was determined in the blood of young (20-40 years) and elderly subjects (64 years or older) at concentrations ranging between 20 and 5000 pg/mL. The effect of selected other drugs on the displacement of [3H] MPA from the binding sites was also investigated. [3H]MPA serum binding (between 81 and 89 %) was similar and concentration independent in the young and elderly subjects and the erythrocyte partitioning coefficient was about 1, indicating the absence of a significant accumulation of MPA in red blood cells. Both the plasma and serum protein binding of [3H] MPA were substantially reduced in the presence of high (> 100 microg/mL) concentrations of salicylic acid. In an in vivo study, the single-dose pharmacokinetics of MPA did not change significantly when misoprostol (200 microg) was given alone or concomitantly with 975 mg of aspirin. These findings indicate that MPA is displaced from its protein binding sites only by high concentrations of salicylic acid and that this displacement is unlikely to be of clinical significance with the usual therapeutic doses of aspirin.

Effects of metronidazole and misoprostol on indomethacin-induced changes in intestinal permeability

In previous open studies, misoprostol and metronidazole reduced nonsteroidal anti-inflammatory drug-induced intestinal permeability changes and inflammation respectively. We assessed the effects of indomethacin treatment (50 mg three times a day) for one week with either coadministered metronidazole (400 mg twice a day, group 1, N = 9) or misoprostol (200 micrograms four times a day, group 2, N = 7) on intestinal permeability to [51Cr]EDTA and mannitol in healthy volunteers, using double-blind, placebo-controlled, randomized techniques. Given alone, neither metronidazole nor misoprostol affected [51Cr]EDTA permeation, whereas indomethacin alone increased it from 1.20 (0.40) [mean percent urinary recovery (SD) groups 1 and 2] to 2.43 (0.72), P < 0.002. Coadministered metronidazole (group 1) prevented this increase [1.10 (0.39) before, 1.55 (0.54) after, P > 0.05], whereas misoprostol (group 2) did not [1.31 (0.51) before, 3.26 (1.10) after, P = 0.005]. No drug regimen altered mannitol permeation. Indomethacin and misoprostol did not affect urinary recovery of intravenously administered probes. The results with metronidazole, if related to its antibacterial effects, support evidence from animal models that bacteria contribute to NSAID-induced intestinal damage. The previously reported reduction of indomethacin-induced increased permeability by misoprostol during a one-day study is not seen when the drugs are used in standard clinical doses for one week.

Renal effects of peptic ulcer therapy

Drugs used in the treatment of peptic ulcer disease may interact with the renal system in a variety of ways. Since many agents are eliminated by renal excretion, clearance of these agents may be reduced and half-life extended in the presence of renal insufficiency. The histamine H2-receptor antagonists may interfere with renal tubular excretion of creatinine and cationic drugs, resulting in elevated serum concentrations and reduced renal clearance. The prostaglandin E1 analogue misoprostol is used as a cytoprotective agent but has renal effects. The renal effects differ between systems studied. In the rat, misoprostol reduces cyclosporin-induced renal tubular toxicity, whereas in humans it has been shown to attenuate renal allograft rejection. Sucralfate is the aluminium salt of sucrose octasulfate. It permits the absorption of aluminium in amounts similar to aluminium-containing antacids, and toxicity has been demonstrated in the presence of renal insufficiency. Bismuth compounds are used increasingly to treat peptic ulcer disease, and bismuth toxicity has been described in association with renal insufficiency. Aluminium-, calcium- and magnesium-containing antacids are used as oral phosphate binders in patients with renal insufficiency in addition to their usual indications. Cation absorption and accumulation with all of these antacid preparations has been described and may lead to toxicity.

Misoprostol--a logical therapeutic approach to gastroduodenal mucosal injury induced by non-steroidal anti-inflammatory drugs?

Misoprostol is a synthetic analogue of naturally occurring prostaglandin E1. The basis of the damaging actions of non-steroidal anti-inflammatory drugs (NSAIDs) on the gastrointestinal (GI) tract is believed to be a consequence of two events: a direct damaging action on mucosal integrity and depletion of endogenous mucosal prostaglandins (PGs). Due to the latter effect, and because current evidence indicates that PGs play an important role in maintaining the integrity of the GI tract, misoprostol has been developed as a logical therapy to prevent and heal gastric and duodenal damage caused by NSAIDs. The purpose of this review is to consider the need for such a therapy, to describe its pharmaceutical development, to review its pharmacology and to review its efficacy compared with other available agents.

Effect of orally administered misoprostol and cimetidine on the steady state pharmacokinetics of diazepam and nordiazepam in human volunteers

The effects of misoprostol and cimetidine on diazepam pharmacokinetics were evaluated in order to determine whether the kinetic variables for diazepam and nordiazepam alone differ with the repeated oral administration of misoprostol and cimetidine to healthy adult volunteers. The trial was conducted as an open crossover study in 12 normal subjects, divided into two groups with all subjects receiving both regimens. Total study duration was 5 weeks. An initial clinical assessment, including blood biochemistry and assessment of subject oxidation status was carried out on study day 1. On this day, subjects began taking diazepam (10 mg) orally for one week, with pharmacokinetic studies performed at day 8, when steady state levels of diazepam were reached. This was followed by one week with active drug, misoprostol to Group I and cimetidine to Group II, with pharmacokinetic studies performed at the end of a 1-week treatment. After a 2-week wash-out period, both groups took for one week, the alternate drug, i.e. cimetidine plus diazepam to Group I and misoprostol plus diazepam to Group II. On days 8, 15 and 36, subjects were admitted to the hospital for 12 h, during which time a clinical examination was carried out and blood samples were taken at time zero and at 4, 8, 12, 24, and 36 h post-dosing for the measurement of serum diazepam and nordiazepam. The main parameters measured and evaluated were diazepam and nordiazepam pharmacokinetics at steady state (days 8, 15 and 36). These were areas under the curve in the dose intervals (AUC0-24h), maximum plasma concentrations (Cmax), time to peak concentrations (Tmax), elimination half-life (t1/2), elimination constant (Kel), distribution volume (Vd), total body clearance (ClB) and clearance after oral administration (Cloral). The results demonstrated that plasma diazepam and nordiazepam concentrations had a significant increase after steady states have been reached with the simultaneous administration of 800 mg of cimetidine daily for one week. The simultaneous administration of 800 micrograms of misoprostol did not cause any significant change in diazepam and nordiazepam plasma levels after steady states had been reached. Comparing the pharmacokinetic parameters of Groups A and B as well as within groups on days 8, 15 and 36, a significant increase in plasma diazepam and nordiazepam levels was detected. This was due to a cimetidine-induced impairment in microsomal oxidation of diazepam and nordiazepam, which caused a decrease in total metabolic clearance and increased mean steady state plasma concentrations. A more prolonged half-life was observed for both groups taking cimetidine as well as an increase of mean maximum plasma concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)

Misoprostol does not alter the pharmacokinetics of propranolol

Twelve healthy volunteers took part in a randomised, double-blind, balanced, cross-over study to investigate the effect of misoprostol on the pharmacokinetics of propranolol. The subjects took propranolol 80 mg twice daily by mouth plus either misoprostol 400 micrograms twice daily or placebo by mouth for 14.5 days, followed by a 2-week washout period, followed by the alternate treatment for 14.5 days. Misoprostol had no significant effect on the t/2, Cmax or AUC of propranolol either after a single dose or at steady state.

Expression of gastric antisecretory and prostaglandin E receptor binding activity of misoprostol by misoprostol free acid

In enriched canine parietal cell preparations, misoprostol, an analog of prostaglandin E1 methyl ester, was rapidly deesterified to misoprostol free acid. Under this circumstance, misoprostol and misoprostol free acid exhibited equal antisecretory potency against histamine-stimulated acid secretion and bound equally well to prostaglandin E receptors. When the deesterification of misoprostol was inhibited by paraoxon, an esterase inhibitor, the antisecretory and receptor binding activity of misoprostol was markedly reduced, with potency much less than misoprostol free acid. These results indicate that misoprostol free acid is the active biological form of misoprostol that binds to prostaglandin E receptors and mediates the antisecretory action of misoprostol.

The effect of the prostaglandin analogue-misoprostol on rat liver mitochondria after chronic alcohol feeding

Rats fed ethanol (36% of total calories in a nutritionally adequate liquid diet) for 5 weeks develop functional alterations of hepatic mitochondria and steatosis of the liver. At the fatty liver stage, ADP-stimulated respiration of mitochondria was depressed in ethanol fed rats by 30% (p less than 0.001) with glutamate + malate and by 23% (p less than 0.001) with succinate as substrates. A similar decrease was noted in the respiratory control ratio (RCR) (34% and 29%, respectively). The total lipid content of the liver increased 2.6 fold (p less than 0.001). Mitochondrial dysfunction could be prevented, in part, by the treatment with a synthetic derivative of prostaglandin E1, misoprostol, at a mean daily dose of 80 micrograms/kg of body weight. The RCR with glutamate + malate as substrates was improved by 36% (p less than 0.05). We conclude that misoprostol attenuates several functional alterations in liver mitochondria during alcohol feeding.

Prostaglandins and gastric ulcers: from seminal vesicle to misoprostol (Cytotec)

Misoprostol (Cytotec, G.D. Searle & Company, Chicago, IL) is the first of a new class of orally administered prostaglandin analog drugs to be marketed in the United States. Misoprostol was approved for the prevention of gastric mucosal ulcers associated with nonsteroidal anti-inflammatory drugs (NSAIDS) in high-risk patients. This represents a potentially important development in the pharmacotherapy of peptic ulcer disease. The purposes of this article are to review (1) the biochemistry, physiology, and pharmacology of prostaglandins, especially those synthesized by the stomach; (2) the potential role of prostaglandin deficiency in the pathophysiology of gastric ulcer disease; and (3) the role of prostaglandin analogs in the prevention and therapy of gastric ulcer disease and in other conditions. As the mechanism of action of these new drugs differs from that of the histamine H2-receptor antagonists (H2-blockers), prostaglandin analogs will, whenever possible, be compared with the H2-blockers [cimetidine (Tagamet), ranitidine (Zantac), nizatidine (Axid) and famotidine (Pepcid)], currently the cornerstone of peptic ulcer therapy in this country.

Misoprostol: discovery, development, and clinical applications

Misoprostol is a synthetic 15-deoxy-16-hydroxy-16-methyl analog of PGE1, and the first prostaglandin to be registered for the treatment of peptic ulcer disease. Misoprostol is a safe and well-tolerated drug that exerts potent gastric antisecretory effects and mucosal protective actions on the gastric and duodenal mucosa. In a dosage of 800 micrograms daily in two or four divided doses, misoprostol produced rates of complete ulcer healing in both gastric and duodenal ulcer patients significantly superior to placebo and comparable to H2 receptor antagonists. The major adverse effect is diarrhea in about 10% of patients, but this is usually mild and self-limiting. Misoprostol possesses uterotonic activity and should not be used in pregnant women or those who wish to become pregnant. Misoprostol effectively heals and prevents NSAID-induced gastropathy, a therapeutic need previously unserved. Due to its mucosal protective properties, misoprostol may have advantages over antisecretory drugs in the compromised patient who is a chronic smoker or alcohol user, in refractory duodenal ulcer patients, in recurrent ulcer, and in emergency use for acute upper GI bleeding. Misoprostol's tissue-protective effects may also extend to other therapeutic areas.

Misoprostol: a prostaglandin E1 analog with antisecretory and cytoprotective properties

Misoprostol, a methylester analog of prostaglandin E1, with antisecretory and cytoprotective properties, has undergone extensive investigation and has received Food and Drug Administration approval for the prevention of nonsteroidal-induced ulceration. The drug represents the first synthetic, orally active prostaglandin evaluated for the treatment of peptic ulcer disease. Clinical studies reveal a trend toward slightly lower healing rates with misoprostol when compared with histamine (H2)-receptor antagonists in the treatment of gastric and duodenal ulcers. In addition, misoprostol was less effective than H2-blockers in reducing ulcer pain, and caused a higher incidence of adverse reactions, particularly diarrhea occurring in up to 13 percent of the patients treated. Several studies have shown misoprostol to be superior to cimetidine and sucralfate in the prevention of alcohol- and drug-induced gastritis. This report summarizes the biopharmaceutics, pharmacokinetics, and clinical efficacy of misoprostol in the treatment of gastric and duodenal ulcers and in the prevention of mucosal injury.

Antisecretory activity of misoprostol, its racemates, stereoisomers and metabolites in isolated parietal cells

Inhibition of histamine-stimulated acid secretion by misoprostol was compared to its racemates, stereoisomers and metabolites in isolated canine parietal cell preparations. The concentration of misoprostol required to inhibit 50% of maximal histamine-stimulated acid secretion (IC50) was 3.8 +/- 0.3 nM. One racemate of misoprostol was at least 1000 times more potent than the other. Of the four misoprostol stereoisomers, the 11R, 16S isomer exhibited the most potent activity against histamine with an IC50 value of 1.4 +/- 0.1 nM. The acid metabolite of misoprostol was equally potent as misoprostol. In contrast to the acid metabolite, the beta-oxidation metabolites of misoprostol lacked significant activity at 1 microM. The results indicate that: 1) the acid metabolite of misoprostol may play a significant role in the antisecretory activity of misoprostol, and 2) the high degree of stereo-specificity associated with the antisecretory effects indicates that the activity of misoprostol may be receptor mediated.

Misoprostol. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in the treatment of peptic ulcer disease

Misoprostol is an analogue of prostaglandin E1 and is the first synthetic prostaglandin analogue to be made available for the treatment of peptic ulcer disease. It inhibits gastric acid secretion in man, and there is also some evidence that it limits the extent of gastrointestinal damage induced by ulcerogenic agents in animals and healthy volunteers at doses lower than those required to inhibit acid secretion. This 'cytoprotective' activity has been explained by several mechanisms, but its contribution to the clinical efficacy of misoprostol in healing established ulcers is doubtful since the drug does not appear to be effective in healing peptic ulcers at non-antisecretory dosages. In clinical trials, ulcer healing has been reported in 60 to 85% of patients with duodenal ulcers and 32 to 54% with gastric ulcers receiving misoprostol 200 micrograms 4 times daily for 4 weeks--the recommended dosage. In comparative studies, the percentage of patients with healed ulcers after misoprostol (800 micrograms daily) was not significantly different from that with cimetidine (1200 mg daily), although there was greater pain relief with cimetidine. No study has yet been published concerning the use of misoprostol as maintenance therapy for the prevention of ulcer recurrence, and no long term tolerability data are available. However, in acute ulcer healing studies (2 to 12 weeks in duration) misoprostol has been well tolerated. Diarrhoea was the most commonly reported symptom, and this was only rarely of sufficient severity to interfere with treatment. No evidence of histopathological changes in the gastric mucosa induced by misoprostol have been reported in man. Evidence of uterine stimulant effects in women receiving misoprostol during the first trimester of pregnancy has resulted in the drug being contraindicated during pregnancy. Thus, misoprostol is a new type of antiulcer drug, providing an alternative approach to the therapy of peptic ulcer disease. It has been shown to be effective and well tolerated in the healing of both gastric and duodenal ulcers. Future studies need to identify the specific types of patients likely to obtain most benefit from treatment, in order to define more clearly the place of misoprostol in the treatment of these indications, as well as addressing the possibility of ulcer prevention with lower doses of misoprostol.