Methylergonovine Maleate
Indications: Obstetrics, adjunct
DESCRIPTION:
methylergonovine maleate is a semi-synthetic ergot alkaloid used for the prevention and control of postpartum hemorrhage.
Methergine is available in sterile ampuls of 1 ml, containing 0.2 mg methylergonovine maleate for intramuscular or intravenous injection and in tablets for oral ingestion containing 0.2 mg methylergonovine maleate.
Methergine Tablets: Active Ingredient: methylergonovine maleate USP, 0.2 mg Inactive Ingredients: acacia, carnauba wax, D&C Red #7, FD&C Blue #1, lactose, mixed parabens, povidone, sodium benzoate, starch, stearic acid, sucrose, talc, tartaric acid, and titanium dioxide.
Methergine Ampuls: 1 ml, clear, colorless solution Active Ingredient: methylergonovine maleate USP, 0.2 mg Inactive Ingredients: sodium chloride USP 3 mg, tartaric acid NF 0.25 mg, water for injection USP qs to 1 ml.
Chemically, methylergonovine maleate is designated as ergoline-8-carboxamide, 9,10-didehydro-N -(1-(hydroxymethyl)propyl)-6-methyl-, (8beta(S ))-, (Z )-2-butenedioate (1:1) (salt).
C20H25N3O2 Β· C4H4O4
Molecular weight: 455.51
CLINICAL PHARMACOLOGY:
Methylergonovine maleate acts directly on the smooth muscle of the uterus and increases the tone, rate, and amplitude of rhythmic contractions. Thus, it induces a rapid and sustained tetanic uterotonic effect which shortens the third stage of labor and reduces blood loss. The onset of action after IV administration is immediate; after IM administration, 2-5 minutes, and after oral administration, 5-10 minutes.
Pharmacokinetic studies have utilized radioimmunoassay techniques. After IV injection of 0.2 mg. methylergonovine maleate is rapidly distributed from plasma to peripheral tissues within an alpha-phase half-life of 2-3 minutes or less. The beta-phase elimination half-life is 20-30 minutes or more, but clinical effects continue for about 3 hours.1,2
Intramuscular injection of 0.2 mg afforded peak plasma concentrations of over 3 ng/ml at tmax of 0.5 hours. After 2 hours, total plasma clearance was 120-240 ml/minute.
After oral administration, bioavailability was reported as 60% with no cumulation after repeated doses. During delivery with parenteral injection, bioavailability increased to 78%.
Excretion is rapid and appears to be partially renal and partially hepatic. Whether the drug is able to penetrate the blood/brain barrier has not been determined.
INDICATIONS AND USAGE:
For routine management after delivery of the placenta; postpartum atony and hemorrhage; subinvolution. Under full obstetric supervision, it may be given in the second stage of labor following delivery of the anterior shoulder.
CONTRAINDICATIONS:
Hypertension; toxemia; pregnancy; and hypersensitivity.
WARNINGS:
This drug should not be administered IV routinely because of the possibility of inducing sudden hypertensive and cerebrovascular accidents. If IV administration is considered essential as a lifesaving measure, methylergonovine maleate should be given slowly over a period of no less than 60 seconds with careful monitoring of blood pressure.
PRECAUTIONS:
General
Caution should be exercised in the presence of sepsis, obliterative vascular disease, hepatic or renal involvement. Also use with caution during the second stage of labor. The necessity for manual removal of a retained placenta should occur only rarely with proper technique and adequate allowance of time for its spontaneous separation.
Carcinogenesis, Mutagenesis, and Impairment of Fertility
No long-term studies have been performed in animals to evaluate carcinogenic potential. The effect of the drug on fertility has not been determined.
Pregnancy Category C
Animal reproductive studies have not been conducted with methylergonovine maleate. It is also not known whether drug methylergonovine maleate can cause fetal harm or can affect reproductive capacity. Use of methylergonovine maleate is contraindicated during pregnancy. (See INDICATIONS AND USAGE)
Labor and Delivery
The uterotonic effect of methylergonovine maleate is utilized after delivery to assist involution and decrease hemorrhage, shortening the third stage of labor.
Nursing Mothers
Methylergonovine maleate may be administered orally for a maximum of 1 week postpartum to control uterine bleeding. Recommended dosage is 1 tablet (0.2 mg) 3 or 4 times daily. At this dosage level a small quantity of drug appears in mothers' milk. Adverse effects have not been described, but caution should be exercised when methylergonovine maleate is administered to a nursing women.
DRUG INTERACTIONS:
Caution should be exercised when methylergonovine maleate is used concurrently with other vasoconstrictors or ergot alkaloids.
ADVERSE REACTIONS:
The most common adverse reaction is hypertension associated in several cases with seizure and/or headache. Hypotension has also been reported. Nausea and vomiting have occurred occasionally. Rarely observed reactions have included, in order of severity: transient chest pains, dyspnea, hematuria, thrombophlebitis, water intoxication, hallucinations, leg cramps, dizziness, tinnitus, nasal congestion, diarrhea, diaphoresis, palpitation, and foul taste.3
DRUG ABUSE AND DEPENDENCE:
Methylergonovine maleate has not been associated with drug abuse or dependence of either a physical or psychological nature.
OVERDOSAGE:
Symptoms of acute overdose may include: nausea, vomiting, abdominal pain, numbness, tingling of the extremities, rise in blood pressure, in severe cases followed by hypotension, respiratory depression, hypothermia, convulsions, and coma.
Because reports of overdosage with methylergonovine maleate are infrequent, the lethal dose in humans has not been established. The oral LD50 (in mg/kg) for the mouse is 187, the rat 93, and the rabbit 4.5.4 Several cases of accidental methylergonovine maleate injection in newborn infants have been reported, and in such cases 0.2 mg represents an overdose of great magnitude. However, recovery occurred in all but one case following a period of respiratory depression, hypothermia, hypertonicity with jerking movements, and, in one case, a single convulsion.
Also, several children 1-3 years of age have accidentally ingested up to 10 tablets (2 mg) with no apparent ill effects. A postpartum patient took 4 tablets at one time in error and reported paresthesias and clamminess as her only symptoms.
Treatment of acute overdosage is symptomatic and includes the usual procedures of:
1. removal of offending drug by inducing emesis, gastric lavage, catharsis, and supportive diuresis.
2. maintenance of adequate pulmonary ventilation, especially if convulsions or coma develop.
3. correction of hypotension with pressor drugs as needed.
4. control of convulsions with standard anti-convulsant agents.
5. control of peripheral vasospasm with warmth to the extremities if needed.5
DOSAGE AND ADMINISTRATION:
Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration.
Intramuscularly: 1 ml, 0.2 mg, after delivery of the anterior shoulder, after delivery of the placenta, or during the puerperium. May be repeated as required, at intervals of 2-4 hours.
Intravenously: Dosage same as intramuscular. (See WARNINGS)
Orally: One tablet, 0.2 mg, 3 or 4 times daily in the puerperium for a maximum of 1 week.
Store and Dispense
Tablets: Below 77Β°F; tight, light-resistant container.
Ampuls: Below 77Β°F; protect from light - administer only if solution is clear and colorless.
REFERENCES:
1. Mantyla, R. and Kants, J.: Clinical Pharmacokinetics of Methylergometrine (Methylergonovine). Int. J. Clin. Pharmacol. Ther. Toxicol. 19(9):386-391, 1981.
2. Iwamura, S. and Kambegawa, A.: Determinations of Methylergometrine and Dihydroergotoxine in Biological Fluids. J. Pharm. Dyn. 4: 275-281, 1981
3. Information on Adverse Reactions supplied by Medical Services Dept., Sandoz Pharmaceuticals, E. Hanover, N.J., based on computerized clinical reports.
4. Berde, B. and Schild, H.O.: Ergot Alkaloids and Related Compounds , Springer-Verlag, New York, 1978, p. 810
5. Treatment of Acute Overdosage. Sandoz Dorsey Rx Products. Sandoz Inc., Medical Services Department.