Ritodrine

Uses

Ritodrine is used for the treatment of uncomplicated premature labour

Ritodrine is also used to associated treatment for these conditions: Foetal distress syndrome, Premature Births, Premature Labour, Uterine Contractions

How Ritodrine works

Ritodrine is beta-2 adrenergic agonist. It binds to beta-2 adrenergic receptors on outer membrane of myometrial cell, activates adenyl cyclase to increase the level of cAMP which decreases intracellular calcium and leads to a decrease of uterine contractions.

Dosage

Ritodrine dosage

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

Side Effects

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.

Toxicity

LD₅₀=64mg/kg (mice, IV); LD₅₀=540 mg/kg (mice, oral); LD₅₀=85 mg/kg (rat, IV)

Precaution

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.

Interaction

Increased risk of hypokalamia if high doses of corticosteroids, diuretics (acetazalamide, loop diuretics and thiazides) or theophylline given with high doses of ritodrine. A sufficient time interval should elapse prior to administration of another sympathomimetic drug. β–adrenergic blocking drugs inhibit its action; coadministraton of these drugs should, therefore, be avoided. With anesthetics used in surgery, the possibility that hypotensive effects may be potentiated should be considered.

Food Interaction

Ritodrine Drug Interaction

Moderate: promethazineMinor: betamethasoneUnknown: imiquimod topical, zolpidem, benzocaine topical, cefazolin, hydralazine, phytonadione, donepezil, diphenhydramine, dinoprostone topical, meperidine, erythromycin ophthalmic, methylergonovine, ibuprofen, acetaminophen / oxycodone, metoclopramide, rho , acetaminophen, acetaminophen / codeine

Half Life

1.7-2.6 hours

Pregnancy & Breastfeeding use

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.

Contraindication

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.

Acute Overdose

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 usedas an antidote.

Storage Condition

Keep away from the reach of the children. Store in cool & dry place protected from light

Innovators Monograph

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