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

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.

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.

Single-dose pharmacokinetics of orally and rectally administered misoprostol in adult horses

OBJECTIVE

To characterize the pharmacokinetics of a clinically relevant dose of misoprostol administered PO or per rectum (PR) to horses.

ANIMALS

8 healthy adult horses.

PROCEDURES

In a randomized 3-way crossover design, horses received a single dose of misoprostol (5 μg/kg) administered PO (with horses fed and unfed) and PR, with a minimum 3-week washout period separating the experimental conditions. Blood samples were obtained before and at various points after drug administration (total, 24 hours), and plasma concentrations of misoprostol free acid were measured.

RESULTS

Mean maximum plasma concentration of misoprostol was significantly higher in the PR condition (mean ± SD, 967 ± 492 pg/mL) and unfed PO condition (655 ± 259 pg/mL) than in the fed PO condition (352 ± 109 pg/mL). Mean area under the concentration-versus-time curve was significantly lower in the PR condition (219 ± 131 pg•h/mL) than in the unfed (1,072 ± 360 pg•h/mL) and fed (518 ± 301 pg•h/mL) PO conditions. Mean time to maximum concentration was ≤ 30 minutes for all conditions. Mean disappearance half-life was shortest in the PR condition (21 ± 29 minutes), compared with values for the unfed (170 ± 129 minutes) and fed (119 ± 51 minutes) PO conditions. No adverse effects were noted.

CONCLUSIONS AND CLINICAL RELEVANCE

Misoprostol was rapidly absorbed and eliminated regardless of whether administered PO or PR to horses. Rectal administration may be a viable alternative for horses that cannot receive misoprostol PO, but this route may require more frequent administration to maintain therapeutic drug concentrations.

Pharmacokinetics and ex vivo anti-inflammatory effects of oral misoprostol in horses

BACKGROUND

Misoprostol is an E prostanoid (EP) 2, 3 and 4 receptor agonist that is anecdotally used to treat and prevent NSAID-induced GI injury in horses. Misoprostol elicits anti-inflammatory effects in vivo in men and rodents, and inhibits TNFα production in equine leucocytes in vitro.

OBJECTIVE

Define the pharmacokinetic parameters of oral misoprostol in horses, and determine the inhibitory effect of oral misoprostol administration on equine leucocyte TNFα production in an ex vivo inflammation model.

STUDY DESIGN

Pharmacokinetic study, ex vivo experimental study.

METHODS

Six healthy adult horses of mixed breeds were used. In phase one, horses were given 5 μg/kg misoprostol orally, and blood was collected at predetermined times for determination of misoprostol free acid (MFA) by UHPLC-MS/MS. Pharmacokinetic parameters were calculated. In phase two, horses were dosed as in phase one, and blood was collected at T0, 0.5, 1 and 4 h following misoprostol administration for leucocyte isolation. Leucocytes were stimulated with 100 ng/mL LPS, and TNFα mRNA concentrations were determined via quantitative real-time PCR.

RESULTS

About 5 μg/kg oral misoprostol produced a rapid time to maximum concentration (Tmax ) of 23.4 ± 2.4 min, with a maximum concentration (Cmax ) of 0.29 ± 0.07 ng/mL and area under the curve (AUC0-∞ ) of 0.4 ± 0.12 h ng/mL. LPS stimulation of equine leucocytes ex vivo significantly increased TNFα mRNA concentrations, and there was no significant effect of misoprostol even at the Tmax .

MAIN LIMITATIONS

Only a single dose was used, and sample size was small.

CONCLUSIONS

Misoprostol is rapidly absorbed following oral administration in horses, and a single 5 μg/kg dose had no significant inhibitory effect on ex vivo LPS-stimulated TNFα mRNA production in leucocytes. Further studies analysing different dosing strategies, including repeat administration or combination with other anti-inflammatory drugs, are warranted.

The Pharmacokinetics of Beraprost Sodium Following Single Oral Administration to Subjects With Impaired Kidney Function

The purpose of the present study was to evaluate the pharmacokinetics of beraprost sodium (BPS) and its active enantiomer, BPS-314d, in Japanese subjects with impaired kidney function. The plasma and urine concentrations of BPS and BPS-314d were measured following the single oral administration of 120 μg of BPS as the sustained-release tablet, TRK-100STP, under fasting conditions to 18 subjects with impaired kidney function (stage 2, 3, and 4 chronic kidney disease [CKD] as categorized by the estimated glomerular filtration rate) and to 6 age-, body weight-, and gender-matched subjects with normal kidney function (stage 1 CKD). The C_max values (mean ± SD) of BPS in stage 1, 2, 3, and 4 CKD, respectively, were 84.9 ± 22.9, 119.8 ± 36.4, 190.6 ± 137.3, and 240.2 ± 110.5 pg/mL; its AUC_0-48h were 978 ± 226, 1252 ± 427, 1862 ± 964, and 1766 ± 806 pg·h/mL, respectively, and its cumulative urinary excretion rates were 0.704 ± 0.351%, 0.638 ± 0.292%, 0.485 ± 0.294%, and 0.159 ± 0.136%. The C_max values of BPS-314d were 22.4 ± 6.4, 30.8 ± 8.5, 46.7 ± 30.6, and 54.4 ± 25.2 pg/mL, its AUC_0-48h were 155 ± 56, 226 ± 67, 341 ± 176, and 329 ± 143 pg·h/mL, and its cumulative urinary excretion rates were 0.428 ± 0.242%, 0.349 ± 0.179%, 0.356 ± 0.270%, and 0.096 ± 0.099%, respectively. Adverse events were reported in 2 subjects with stage 2 CKD and 1 subject with stage 4 CKD. The C_max and AUC_0-48h of BPS and BPS-314d were higher based on the severity of impaired kidney function. No relationship was observed between the incidence of adverse events and the severity, and tolerability was confirmed. We consider that dose adjustment is not necessary, but BPS is more carefully treated in patients with impaired kidney function.

The use of misoprostol in termination of second-trimester pregnancy

Misoprostol, a synthetic prostaglandin E1 analog, is initially used to prevent peptic ulcer. The initial US Food and Drug Administration-approved indication in the product labeling is the treatment and prevention of intestinal ulcer disease resulting from nonsteroidal anti-inflammatory drugs use. In recent two decades, misoprostol has approved to be an effective agent for termination of pregnancy in various gestation, cervical ripening, labor induction in term pregnancy, and possible management of postpartum hemorrhage. For the termination of second-trimester pregnancy using the combination of mifepristone and misoprostol seems to have the highest efficacy and the shortest time interval of abortion. When mifepristone is not available, misoprostol alone is a good alternative. Misoprostol, 400 μg given vaginally every 3-6 hours, is probably the optimal regimen for second-trimester abortion. More than 800 μg of misoprostol is likely to have more side effects, especially diarrhea. Although misoprostol can be used in women with scarred uterus for termination of second-trimester pregnancy, it is recommended that women with a scarred uterus should receive lower doses and do not double the dose if there is no initial response. It is also important for us to recognize the associated teratogenic effects of misoprostol and thorough consultation before prescribing this medication to patients regarding these risks, especially when failure of abortion occurs, is needed.

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.

Mid-trimester induced abortion: a review

Mid-trimester abortion constitutes 10-15% of all induced abortion. The aim of this article is to provide a review of the current literature of mid-trimester methods of abortion with respect to efficacy, side effects and acceptability. There have been continuing efforts to improve the abortion technology in terms of effectiveness, technical ease of performance, acceptability and reduction of side effects and complications. During the last decade, medical methods for mid-trimester induced abortion have shown a considerable development and have become safe and more accessible. The combination of mifepristone and misoprostol is now an established and highly effective method for termination of pregnancy (TOP). Advantages and disadvantages of medical versus surgical methods are discussed. Randomized studies are lacking, and more studies on pain treatment and the safety of any method used in patients with a previous uterine scar are debated, and data are scarce. Pain management in abortion requires special attention. This review highlights the need for randomized studies to set guidelines for mid-trimester abortion methods in terms of safety and acceptability as well as for better analgesic regimens.

Vaginal Misoprostol Administration for Cervical Ripening and Labor Induction

Intravaginal misoprostol has been shown to be an effective agent for cervical ripening and induction of labor. Vaginal application of misoprostol has been reported in over 9000 women worldwide and seems to have safety profile similar to that of endocervically and intravaginally administered dinoprostone. Concern arises with the use of higher doses of intravaginal misoprostol (50 mcg or more) and the association with uterine contractile abnormalities and for this reason, use of low-dose misoprostol regimen has been recommended by the American College of Obstetricians and Gynecologists. The recommendation is use of a 25-mcg dose of misoprostol inserted into the posterior vaginal fornix and repeated every 3 to 6 hours as needed. Misoprostol administration to women with prior cesarean births seems to increase the likelihood of uterine scar disruption and should not be used in these women. There are reports of uterine rupture in women with unscarred uteri treated with vaginally applied misoprostol. Therefore, all patients need to be monitored adequately after misoprostol administration. Although there is a growing body of data regarding the ambulatory use of intravaginal misoprostol for cervical ripening, its use for this purpose cannot be recommended outside of investigational protocols at this time because of concerns for maternal and neonatal safety.

Review of medical abortion using mifepristone in combination with a prostaglandin analogue

Induced abortion is still a major health problem in the world and the most frequently performed intervention in obstetrics and gynecology with an estimated total of 46 million worldwide each year. Medical abortion with mifepristone and prostaglandin was first introduced in 1988 and is now approved in 31 countries. This combination of drugs has recently been included in the List of Essential Medicines by the World Health Organisation. The present review summarizes the development, physiology and the development of the currently used regimens.

Oral misoprostol and uterine rupture in the first trimester of pregnancy: A case report

We are reporting the case of a woman with 8 weeks of amenorrhea who orally received a single dose of misoprostol 400 microg at midnight for ripening of cervix before uterine evacuation of an intrauterine gestational sac containing a single fetus (6.3 weeks of gestation) without cardiac activity. The patient had severe abdominal pain an hour later. Her blood pressure was 70/40 mmHg and her abdomen was slightly distended with direct and rebound tenderness. A transvaginal ultrasonography showed a 3-cm depth of a free fluid collection in the rectouterine pouch. Her hemoglobin and hematocrit levels were of 6.5 g/dL and 18.4%, respectively. A rupture of 1.5 cm at the left uterine horn with a protruding gestational sac was identified by laparoscopy. The gestational sac was removed and hemoperitoneal collection were successfully drained. The site of uterine rupture was primarily sutured and postoperative course was satisfactory. In summary, misoprostol administered in the first trimester of pregnancy may produce uterine rupture.

Misoprostol: A Quarter Century of Use, Abuse, and Creative Misuse

Misoprostol is a prostaglandin E1 analog originally intended for use to prevent NSAID-induced gastric ulcers. However, because of its cervical ripening and uterotonic property, misoprostol has become one of the most useful drugs in obstetrics and gynecology. Misoprostol has proven to be a very convenient and flexible drug because of its formulation as a tablet that is stable and that can be administered orally, rectally, vaginally and by the sublingual route. Beginning with its abuse for illegal abortion in the late 1980s, misoprostol has quickly become established as one of the most effective drugs for terminating pregnancies in the first and second trimesters, as well as for inducing labor in the third trimester. Its use for routine prevention of postpartum hemorrhage has not been so successful, partly as the high doses required for this indication often result in troublesome side effects. Despite the large body of medical evidence about its efficacy and relative safety, the use of misoprostol in pregnant women remained off-label until the spring of 2002.

Evaluation of a novel method to estimate absolute bioavailability of drugs from oral data

The goal of this investigation was to evaluate the performance of a novel method allowing estimation of absolute bioavailability from oral data only. In contrast to the traditional method, which compares areas under the drug concentration time curves after oral and intravenous administration in subjects with normal renal function, the novel method uses total and renal clearance values following oral administration from subjects with varying renal functions to estimate bioavailability. The novel method can also provide estimates for nonrenal clearance.Published data on total clearance and renal clearance of drugs obtained from subjects with variable renal functions were collected, the novel method applied, estimates of bioavailability and nonrenal clearance obtained and compared with reported estimates by the traditional methods. In addition computations were performed to assess various factors that could possibly affect the reliability of the novel method. The results indicated that the novel method provides accurate estimates for bioavailability of drugs meeting the prerequisites: linear kinetics, predominant renal excretion in normals, absence of metabolic polymorphism and independence of bioavailability and nonrenal clearance from renal function. The average (standard deviation) of the prediction error and bias of the bioavailability estimates by the novel method was 7.8 (6.0) and -1.4 (9.8)%, respectively. The estimates for nonrenal clearance by the novel method were less accurate. The computations confirmed that the estimates by the novel method are sensitive to renal-function dependent changes in nonrenal clearance and bioavailability and also depend on the extent of renal excretion of a drug. In conclusion, the novel method's main use is to diagnose absence or presence of changes in bioavailability and non-renal clearance of drugs in populations with varying renal function.

A benefit-risk assessment of misoprostol for cervical ripening and labour induction

Misoprostol, a prostaglandin E(1) analogue, is widely used in the US and other countries for cervical ripening and labour induction. Its use for these indications is not approved by the US Food and Drug Administration (FDA). The manufacturer of misoprostol issued a letter to American healthcare providers in August 2000, cautioning against the use of misoprostol in pregnant women and citing a lack of safety data for its use in obstetrical practice. The only FDA-approved indication in the product labelling is the treatment and prevention of intestinal ulcer disease resulting from nonsteroidal anti-inflammatory drug use. Multiple trials have proven that when applied vaginally, misoprostol is an effective agent for cervical ripening and labour induction in term pregnancy. The use of oxytocin augmentation is reduced when intravaginal misoprostol is used compared with other agents. Misoprostol use in obstetrics carries the added benefits of temperature stability at room temperature, which is unlike other prostaglandin preparations which require refrigeration or freezing, and reduced cost. However, debate continues regarding the optimal dose, dosage regimen, and route of administration. Uterine contraction abnormalities are often found in association with higher misoprostol doses (50 microg or more) given vaginally or orally. Some trials also indicate increased frequencies of meconium passage, neonatal acidaemia and caesarean delivery for fetal distress in women receiving higher doses of vaginally applied misoprostol. However, most trials fail to demonstrate a significant change in the caesarean delivery rate with the use of misoprostol, although a recent meta-analysis indicated that the use of intravaginal misoprostol is associated with a lowering of the caesarean rate when compared with pooled controls. Low-dose misoprostol (25 microg) is an effective agent for cervical ripening and labour induction when used in a judicious and cautious fashion. There are insufficient data to support the widespread use of oral misoprostol for cervical ripening and labor induction. Some trials suggest that this approach may be effective; however, the ideal dose and administration regimen have yet to be defined.

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.

Attenuation of ischemic liver injury by prostaglandin E1 analogue, misoprostol, and prostaglandin I2 analogue, OP-41483

BACKGROUND

Prostaglandin has been reported to have protective effects against liver injury. Use of this agent in clinical settings, however, is limited because of drug-related side effects. This study investigated whether misoprostol, prostaglandin E1 analogue, and OP-41483, prostaglandin I2 analogue, which have fewer adverse effects with a longer half-life, attenuate ischemic liver damage.

STUDY DESIGN

Thirty beagle dogs underwent 2 hours of hepatic vascular exclusion using venovenous bypass. Misoprostol was administered intravenously for 30 minutes before ischemia and for 3 hours after reperfusion. OP-41483 was administered intraportally for 30 minutes before ischemia (2 microg/kg/min) and for 3 hours after reperfusion (0.5 microg/kg/min). Animals were divided into five groups: untreated control group (n=10); high-dose misoprostol (total 100 microg/kg) group (MP-H, n=5); middle-dose misoprostol (50 microg/kg) group (MP-M, n=5); low-dose misoprostol (25 microg/kg) group (MP-L, n=5); and OP-41483 group (OP, n=5). Animal survival, hepatic tissue blood flow (HTBF), liver function, and histology were analyzed.

RESULTS

Two-week animal survival rates were 30% in control, 60% in MP-H, 100% in MP-M, 80% in MP-L, and 100% in OP. The treatments with prostaglandin analogues improved HTBF, and attenuated liver enzyme release, adenine nucleotrides degradation, and histologic abnormalities. In contrast to the MP-H animals that exhibited unstable cardiovascular systems, the MP-M, MP-L, and OP animals experienced only transient hypotension.

CONCLUSIONS

These results indicate that misoprostol and OP-41483 prevent ischemic liver damage, although careful dose adjustment of misoprostol is required to obtain the best protection with minimal side effects.