methylergonovine maleate
Methergine

Available forms
Available by prescription only
Injection: 0.2 mg/ml ampule
Tablets: 0.2 mg

Indications and dosages
 Prevention and treatment of postpartum hemorrhage from uterine atony or subinvolution. Adults: 0.2 mg I.M. or I.V. q 2 to 4 hours for maximum five doses. Following initial I.M. or I.V. dose, may give 0.2 to 0.4 mg P.O. q 6 to 12 hours for maximum 7 days. Decrease dose if severe cramping occurs.
 Diagnosis of coronary artery spasm ◇. Adults: 0.1 to 0.4 mg I.V.

Pharmacodynamics
Oxytocic action: Drug stimulates contractions of uterine and vascular smooth muscle. The intense uterine contractions are followed by periods of relaxation. Drug produces vasoconstriction primarily of capacitance blood vessels, causing increased central venous pressure and elevated blood pressure. Drug increases the amplitude and frequency of uterine contractions and tone, which therefore impedes uterine blood flow.

Pharmacokinetics
Absorption: Absorption is rapid, with 60% of an oral dose appearing in the bloodstream.
Distribution: Distribution appears to be rapidly distributed into tissues.
Metabolism: Extensive first-pass metabolism precedes hepatic metabolism.
Excretion: Excreted primarily in feces, with a small amount in urine.

Contraindications and precautions
Contraindicated in pregnant women and patients with hypertension, toxemia, or sensitivity to ergot preparations. Use cautiously during second stage of labor and in patients with renal or hepatic disease, sepsis, or obliterative vascular disease. Also use cautiously in patients with unstable angina, recent myocardial infarction, coronary artery disease, history of cerebrovascular accident, eclampsia or preeclampsia, and Raynaud’s disease.

Interactions
Drug-drug. Ergot alkaloids, sympathomimetic amines: Enhances vasoconstrictor potential. Use together cautiously.
Local anesthetics with vasoconstrictors (lidocaine with epinephrine): Enhances vasoconstriction. Use together cautiously.
Drug-lifestyle. Smoking (nicotine): Enhances vasoconstriction. Discourage smoking.

Adverse reactions
CNS: dizziness, headache, seizures, CVA (with I.V. use), hallucinations.
CV: hypertension, transient chest pain, palpitations, hypotension, bradycardia.
EENT: tinnitus, nasal congestion.
GI: nausea, vomiting, diarrhea, foul taste.
GU: hematuria.
Musculoskeletal: leg cramps.
Respiratory: dyspnea.
Skin: diaphoresis.
Other: thrombophlebitis.

Effects on lab test results
• May decrease prolactin level.

Overdose and treatment
Signs and symptoms of overdose include seizures, gangrene, nausea, vomiting, diarrhea, dizziness, changing blood pressure, weak pulse, chest pain, abdominal pain, tingling, and numbness and coldness in limbs.
 Treatment of oral overdose requires that the patient drink tap water, milk, or vegetable oil to delay absorption. Follow with gastric lavage or emesis and then activated charcoal and cathartics. Treat seizures with anticonvulsants and hypercoagulability with heparin; use vasodilators to improve blood flow as required. Gangrene may require surgical amputation.

Special considerations
• Contractions begin 5 to 15 minutes after P.O. administration, 2 to 5 minutes after I.M. injection, and immediately following I.V. injection. They continue 3 hours or more after P.O. or I.M. administration, 45 minutes after I.V. delivery.
• Don’t administer I.V. routinely because of the possibility of inducing sudden hypertensive and CV accidents.
• If I.V. administration is considered essential as a life-saving measure, dilute the desired dose with normal saline solution injection to a volume of 5 ml and give slowly over at least 60 seconds.
• Monitor patient’s blood pressure, pulse rate, and uterine response.
• Watch for sudden change in vital signs or frequent periods of uterine relaxation.
• Assess vaginal bleeding.
• Store tablets in tightly closed, light-resistant containers. Discard if discolored.
• Store I.V. solutions below 77° F (25° C). Administer only if solution is clear and colorless.
Breast-feeding patients
• Ergot alkaloids inhibit lactation.
• Drug appears in breast milk, and ergotism has been reported in breast-fed infants.

Patient education
• Advise patient to stop smoking during therapy.
• Warn patient of adverse reactions.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use