Ritodrine, formerly sold under the brand name Yutopar among others, is a tocolytic drug used to stop premature labor. It was withdrawn from the US market, according to the FDA Orange Book. It was available in oral tablets or as an injection and was typically administered for short term suppression of uterine contractions. Chemically ritodrine is a substituted phenylethanolamine with predominant beta-2 adrenergic receptor agonist activity; it produces uterine smooth muscle relaxation by raising intracellular cyclic AMP in myometrial cells, resulting in reduced calcium availability and decreased contractile force. Clinically it was used acutely to delay preterm delivery while antenatal corticosteroids or transport to a tertiary center were arranged. Pharmacokinetic properties include oral and parenteral bioavailability variation, hepatic metabolism to hydroxylated and dealkylated products, and renal elimination of metabolites. Quality control historically relied on HPLC and LC-MS assays for assay, related substances, and enantiomeric composition.
Known related compounds and degradation products for ritodrine include stereoisomeric forms, N-dealkylation products, N-oxide derivatives, oxidative phenolic metabolites, dehydration products and simple ring oxidation products, plus typical process-related impurities and residual solvents. Analytical control typically employs reversed-phase HPLC with UV detection and LC-MS confirmation, and chiral HPLC when enantiomeric purity is required. Typical specification ranges used by manufacturers and compendial monographs for small molecule active pharmaceutical ingredients are: individual specified impurities commonly limited to the range 0.05 to 0.2 percent by weight, total related substances commonly limited to 0.5 to 1.0 percent by weight, and any identified genotoxic impurity controlled to well below 0.05 percent in accordance with ICH M7 thresholds. Residual solvents are controlled to pharmacopeial limits such as methanol not exceeding 3000 ppm when applicable. Exact limits for a marketed or registered ritodrine substance are determined by the product master file, regulatory filings, or a specific pharmacopeial monograph and should be confirmed from those sources.
Ritodrine was used as a tocolytic to suppress preterm uterine contractions and delay delivery for short periods to allow interventions such as maternal corticosteroid administration or transfer to a higher level of care.
Yes. Ritodrine is a beta-2 adrenergic receptor agonist with greater activity on beta-2 receptors in uterine smooth muscle than on beta-1 receptors, which underlies its uterine relaxant properties.
Ritodrine activates beta-2 receptors on myometrial cells, raising intracellular cyclic AMP and activating protein kinase A. This leads to decreased intracellular calcium and reduced phosphorylation of myosin light chain, producing relaxation of uterine smooth muscle and reduced contractility.
Ritodrine was withdrawn from the US market due to safety concerns and changing benefit risk assessments. Reported adverse effects included cardiovascular complications such as tachycardia, pulmonary edema, and other maternal and fetal safety issues; combined with availability of alternative management strategies and regulatory review, those factors led to market withdrawal as recorded in the FDA Orange Book.
