Ritodrine hydrochloride
Ritodrine hydrochloride (Yutopar)
Ritodrine Hydrochloride
( RYE-toe-dreen)
Pregnancy Category: B Ritodrine HCl in 5% Dextrose Yutopar (Rx)

Classification: Uterine relaxant

Action/Kinetics: Stimulates beta-2 receptors of smooth muscle of the uterus, which results in inhibition of uterine contractility. May also directly inhibit the actin-myosin interaction. Beta-adrenergic blocking agents inhibit the drug. Increased blood levels of insulin, glucose, and free fatty acids and decreased levels of potassium have been observed during IV infusion. Onset, IV: 5 min. Peak plasma concentration, IV: After a 9-mg infusion over 60 min, 32-50 ng/mL; PO: after a dose of 10 mg, 5-15 ng/mL. Time to peak serum levels: 20-60 min. t 1/2, after IV: 15-17 hr. Ninety percent of drug excreted within 24 hr through the urine.

Uses: Management of preterm labor in selected clients after week 20 of gestation. When indicated, initiate therapy as early as possible after diagnosis. However, decision to use ritodrine should include determination of fetal maturity.

Contraindications: Before week 20 of pregnancy and when continuation of pregnancy is hazardous to mother (e.g., eclampsia, severe preeclampsia, intrauterine fetal death, antepartum hemorrhage, pulmonary hypertension, chorioamnionitis, and maternal hyperthyroidism, cardiac disease or uncontrolled diabetes mellitus). Also, medical conditions (e.g., uncontrolled hypertension, pheochromocytoma, bronchial asthma, hypovolemia, cardiac arrhythmias due to tachycardia or digitalis toxicity) that would be aggravated by beta-adrenergic agonists. Use in diabetics.

Special Concerns: Maternal pulmonary edema has been noted in women treated with ritodrine. The use in advanced labor (i.e., greater than 4 cm cervical dilation or effacement greater than 80%) has not been established.

Side Effects: All effects are related to the stimulation of beta receptors by the drug. IV. CV: Increase in maternal and fetal HR, increase in maternal systolic and marked decrease in diastolic BP (widening of pulse pressure), persistent tachycardia (may indicate pulmonary edema), palpitations, arrhythmias including VT chest pain or tightness, angina, heart murmur, myocardial ischemia. Sinus bradycardia following drug withdrawal. GI: N&V;, bloating, ileus, epigastric distress, diarrhea or constipation. CNS: Headache, migraine headache, tremors, malaise, nervousness, jitteriness, restlessness, anxiety, emotional changes, drowsiness, weakness. Metabolic: Transient increases in insulin and blood glucose, increases in cyclic AMP and free fatty acids, decrease in potassium, glycosuria, lactic acidosis. Respiratory: Dyspnea, maternal pulmonary edema hyperventilation. Hematologic: Leukopenia or agranulocytosis after 2-3 weeks of IV therapy (leukocyte count returned to normal after cessation of drug). Other: Erythema, anaphylactic shock rash, intrauterine growth retardation, hemolytic icterus, sweating, chills, impaired liver function. NOTE: Neonatal effects are infrequent but may include hypoglycemia and ileus; also, hypocalcemia and hypotension in neonates whose mothers were treated with other betamimetic drugs.

Laboratory Test Alterations: Plasma glucose and insulin; plasma potassium.

Overdose Management: Symptoms: Excessive beta-adrenergic stimulation, including tachycardia (in both the mother and fetus), palpitations, cardiac arrhythmias hypotension, dyspnea, tremor, dyspnea, nervousness, N&V.; Treatment: Supportive measures. A beta-adrenergic blocking agent can be used as an antidote. The drug is dialyzable.

Drug Interactions: Anesthetics, general / Additive hypotension or cardiac arrhythmias Atropine / Systemic hypertension Beta-adrenergic blocking agents / Inhibition of the effect of ritodrine Corticosteroids / Risk of pulmonary edema Diazoxide / Additive hypotension or cardiac arrhythmias Magnesium sulfate / Additive hypotension or cardiac arrhythmias Meperidine / Additive hypotension or cardiac arrhythmias Sympathomimetics / Additive or potentiated effects of sympathomimetics

How Supplied: Injection: 10 mg/mL, 15 mg/mL

Dosage
?IV Preterm labor.
Initial: 0.05 mg/min (10 gtt/min using microdrip chamber); then, depending on response, increase by 0.05 mg/min (10 microdrops/min) q 10 min until desired response occurs. Effective dose range: 0.15-0.35 mg/min (30-70 gtt/min). Continue infusion antepartum for a minimum of 12 hr after contractions cease.