DrugindexOnline^{2nd edition}

Pronouncation: (MY-so-PRAHST-ole)
Class: Prostaglandin

Trade Names:
Cytotec
- Tablets 100 mcg
- Tablets 200 mcg

Apo-Misoprostol (Canada)
Novo-Misoprostol (Canada)

Mechanism of Action

Pharmacology

Synthetic prostaglandin E ₁ analog that inhibits gastric acid secretion and exerts mucosal-protective properties.

Pharmacokinetics

Absorption

Misoprostol is extensively absorbed. T _max is approximately 12 min. Food decreases C _max and total availability of misoprostol acid is reduced by the use of concomitant antacid.

Distribution

Less than 90% is protein bound and displays linear kinetics.

Metabolism

Misoprostol undergoes rapid de-esterification to its free acid, which is responsible for its clinical activity. It does not affect the hepatic mixed function oxidase cytochrome P450 enzyme system.

Elimination

Approximately 80% is detected in urine and the t _½ is 20 to 40 min.

Special Populations

Renal Function Impairment

C _max , AUC, and t _½ are almost doubled, but no clear correlation between degree of impairment and AUC is shown. No dosage adjustment is recommended. However, dose reduction my be needed if patient does not tolerate.

Elderly

AUC is increased in patients older than 64 yr. However, no dose adjustment is needed.

Indications and Usage

Prevention of gastric ulcers in high-risk patients who are taking NSAIDs.

Contraindications

History of allergy to prostaglandins; pregnancy.

Dosage and Administration

Adults

PO 100 to 200 mcg qid, in conjunction with NSAID therapy.

Storage/Stability

Store tablets below 77° F. Protect from moisture.

Drug Interactions

None well documented.

Laboratory Test Interactions

None well documented.

Adverse Reactions

CNS

Headache (2%).

GI

Diarrhea (14% to 40% [dose-related]); abdominal pain (13% to 20%); nausea, flatulence (3%); dyspepsia (2%); vomiting, constipation (1%).

Precautions

Warnings Abortion, premature birth, birth defects, and uterine rupture have been reported when misoprostol is administered in pregnant women to induce labor or abortion beyond week 8 of pregnancy. Misoprostol should not be taken by pregnant women for risk reduction of NSAID ulcers. Counsel patients on abortifacient properties. Monitoring recommendations Prescribe for NSAID ulcer reduction in women only if serum pregnancy test is negative when administered within 2 wk prior to therapy and patient is capable of contraception compliance. Written and oral patient counseling is required. Begin therapy only on second or third day of the next menstrual period.

Pregnancy

Category X .

Lactation

Undetermined.

Children

Safety and efficacy not established in children younger than 18 yr.

Elderly

Reduce dosage if usual dose is not tolerated.

Renal Function

May reduce drug Cl; routine dosage adjustment is not recommended unless usual dose is not tolerated.

Fertility

May adversely affect fertility.

Diarrhea

Dose related (13% to 40%); usually develops early in course of therapy (after 13 days) and is usually self-limiting (resolving after 8 days).

Duodenal ulcers

Not for prevention of duodenal ulcers in patients on NSAIDs.

Overdosage

Symptoms

Sedation, tremor, seizure, dyspnea, abdominal pain, diarrhea, fever, palpitations, hypotension, bradycardia.

Patient Information

• Explain name, dose, action, and potential side effects of drug.
• Advise patient to read Patient Information leaflet before starting therapy and with each refill.
• Advise patient that medication is not used to treat stomach ulcers but is being used to prevent the NSAID from causing stomach ulcers and that the medication must be taken regularly, as prescribed, for this beneficial effect to occur.
• Advise patient to take prescribed dose with or after a meal to reduce risk of diarrhea.
• Advise patient to take the last dose of the day just before bedtime.
• Caution patient not to change the dose or stop taking unless advised by health care provider.
• Advise patient that diarrhea is the most common side effect of misoprostol and that taking each dose with or after meals and avoiding magnesium-containing antacids may minimize this problem.
• Advise patient to notify health care provider if symptoms of stomach ulcer develop (eg, indigestion, stomach pain), or if intolerable side effects (eg, diarrhea, cramping) develop.
• Caution women of childbearing potential to use an effective method of contraception while taking this medication and for 1 mo or for 1 menstrual cycle after misoprostol has been discontinued.
• Advise women to notify health care provider if pregnant, planning to become pregnant, or breastfeeding.
• Advise patient not to take any prescription or OTC drugs or dietary supplements without consulting health care provider.
• Advise patient that follow-up visits may be necessary to monitor therapy and to keep appointments.