<prompt> Drug of choice to delay preterm labour:RitodrineNifedipineProgesteroneIndomethacin  <response>: Ans: B A Nifedipine RitodrineRef: DC Duttas Textbook of Obstetrics, pg: 508Explanation:Best answer would be b Nifedipine Most likely a Ritodrine as there is no clear first-line tocolytic agent.Common Tocolytic Agents, Their Mechanism and Side Effects DrugMechanismDescriptionPossiblecontraindicationsMaternal side effectsFetal and neonatal side effectsTerbutalineb2-agonistIs often the drug given first, especially if there is only low risk of preterm birthCardiac arrhythmias diabetes Cardiac arrhythmias Cardiopulmon ary diseases Pulmonary- edema Myocardial ischemia Hypertension Tachycardia Fetal tachycardia Hyperinsulinemia Hypoglycemia Myocardial and septal hypertrophy Myocardial ischemiaRitodrineb2-agonistNo longer had FDA approvedPoorly controlled thyroid disease and diabetesMetabolic hyperglycemia Hyperinsulinemia Hypokalemia Antidiuresis Altered thyroid function Physiologic tremor Palpitations Nervousness Nausea or vomiting Fever Hallucinations Neonatal tachycardia Hypoglycemia Hypocalcemia Hyperbilirubinemia Hypotension Intraventricular hemorrhageNifedipineCCBsIs one of the most commonly used tocolytic agentsCardiac disease It should not be used concomitantly with magnesium sulfate Flushing Headache Dizziness Nausea Transient hypotension. Renal disease and hypotension. Concomitant use of calcium channel blockers and magnesium sulfate may result in cardiovascular collapse None noted as yetAtosibanOxytocinantagonistless side effects than 62 recep agonist IndomethacinNSAIDs Late pregnancy ductus arteriosus, significant renal or hepathic Impairment Nausea Heartburn Constriction of ductus arteriosus Pulmonary hypertension Reversibe decrease in renal unction with oligohydramnios intraventricular hemorrhage Hyperbilirubinemia Necrotizing enterocolitisSulindacNSAIDs Coagulation disorders or thrombocytopenia, nonsteroidal anti-inflammatory drug MSAID-sensitive asthma, other sensitivity to NSAIDs IVMagnesiumsulfateMyosin lightchaininhibitorShewn to be ineffective.Has been recommended for women at high risk. However, meta-analyses have failed to support it as a tocolytic agent.AbsolutecontraindicationMyasthenia gravis Flushing Lethargy Headache Muscle weakness Diplopia Dry mouth Pulmonary edema Cardiac arrest Lethargy Hypotonia Respiratory depression Derrl penalization with prolonged useCalcium-channel blockers and an oxytocin antagonist can delay delivery by 2.7 days. Otherwise tocolysis is rarely successful beyond 24-48 hours because current medications do not alter the fundamentals of labor activation.However, just gaining 48 hours is sufficient to allow the pregnant women to be transferred to a center specialized for management of preterm deliveries and administer corticosteroids to reduce the possibility of neonatal organ immaturity.Contraindications to TocolysisGestational age 34 weeks gestation.Intrauterine Growth Restriction IUGR or placental insufficiency.Lethal congenital or chromosomal abnormalities.Cervical dilation 4 cm.Chorioamnionitis or intrauterine infection.Fetal distress or fetal death.Mother has severe pregnancy-induced hypertension.Eclampsiapreeclampsia.Active vaginal bleeding.Placental abruption.Cardiac disease. 