A selective β2-adrenoceptor agonist with its main action on the uterus, causing relaxation. It reduces the intensity and frequency of contractions. Heart rate is also increased while diastolic pressure is reduced. May cause bronchial relaxation but this is not clinically significant in its usage.

Ritodrine is indicated for the treatment of uncomplicated premature labour

By intravenous infusion: Initially 50 mcg/minute, increased gradually according to response by 50 mcg/minute every 10 minutes until contractions stop or maternal heart rate reaches 140 beats/minute; continue for 12–48 hours after contractions cease (usual rate 150–350 mcg/minute); maximum rate 350 mcg/minute.

Intramuscular injection: 10 mg in every 3–8 hours continued for 12–48 hours after contractions have ceased; then by mouth.

Oral maintenance treatment: One tablet (10 mg) may be given approximately 30 minutes before termination of intravenous therapy, repeated every 2 hours for 24 hours, followed by 10–20 mg every 4–6 hours, maximum oral dose 120 mg daily

It is contraindicated in patients with known hypersensitivity to the active ingredient or any of the excipients of this component. β2-agonists are contra-indicated in cardiac disease and in patients with significant risk factors for myocardial ischaemia; they should also be avoided in antepartum haemorrhage, intra-uterine infection, intra-uterine fetal death, placenta praevia, abruptio placenta, threatened miscarriage, cord compression, and eclampsia or severe preeclampsia.

The common side-effects of ritodrine hydrochloride are nausea, vomiting, flushing, sweating, tremor, hypokalaemia, tachycardia, palpitations, hypotension (left lateral position throughout infusion to minimize risk), uterine bleeding, pulmonary oedema; chest pain or tightness, arrhythmias and salivary gland enlargement. On prolonged administration for several weeks may cause leucopenia and agranulocytosis; liver function abnormalities including increased transaminases and hepatitis.

Overdose Effects

Symptoms of overdosage are tachycardia (maternal and fetal), palpitation, cardiac arrhythmia, hypotension, nervousness, tremor, nausea and vomiting. If an excess of ritodrine tablets is ingested, gastric lavage or induction of emesis should be carried out followed by administration of activated charcoal. When symptoms of overdose occur as a result of parenteral administration, ritodrine should be discontinued; an appropriate β-blocking agent may be used

It should be used cautiously in patient with suspected cardiac diseases, hypertension, hyperthyroidism, hypokalaemia, diabetes mellitus, mild to moderate preeclampsia, monitor blood pressure and pulse rate and avoid over-hydration during taking ritodrine hydrochloride.

Pregnancy & Lactation

Ritodrine is a drug of pregnancy category B. There are no adequate and well controlled studies of effects in pregnant women before 20 weeks gestation; therefore, this drug should not be used before the 20th week of pregnancy. Studies in pregnant women from the 20th week of gestation onwards have not shown increased risk of fetal abnormalities. Nonetheless, although clinical studies did not indicate a risk of permanent adverse fetal effects from ritodrine, the possibility cannot be excluded; therefore, it should be used only when clearly indicated. In frequently reported neonatal symptoms include hypoglycemia and ileus. In addition, hypocalcemia and hypotension have been reported in neonates whose mothers were treated with other beta mimetic agents. Caution should be exercised unless the potential benefit of treatment to the mother outweighs any possible risk of the infants.