Classifications: autonomic nervous system agent; beta-adrenergic agonist
Prototype: Isoproterenol
Pregnancy Category: C


10 mg/mL, 15 mg/mL, 0.3 mg/mL injection


Preferentially stimulates beta2-receptors in uterine smooth muscle, reducing intensity and frequency of uterine contractions and lengthening gestation period. (Actions may be eliminated by beta-adrenergic antagonists.) Transitory cardiovascular effects include increased cardiac output, increased maternal and fetal heart rates, and widening of maternal pulse pressure (beta1 stimulation).

Therapeutic Effects

Beta2- adrenergic agonist clinically effective in preventing or delaying preterm labor (tocolytic effect). Uterine contractions will decrease in frequency and intensity during treatment.


To manage premature labor in selected patients.


Mild to moderate preeclampsia or eclampsia, intrauterine infection, cervix dilated 4 cm or more (in a single pregnancy); pregnancy (category C); hypertension; diabetes mellitus; prior to 20th wk or after 36th wk of pregnancy or if continuation of pregnancy would be hazardous to mother and fetus (e.g., antepartum hemorrhage, eclampsia, intrauterine fetal death, maternal cardiac disease, pulmonary hypertension, maternal hyperthyroidism, severe diabetes mellitus). Also hypovolemia, cardiac arrhythmias associated with tachycardia or digitalis intoxication, uncontrolled hypertension; thyrotoxicosis; bronchial asthma being treated with betamimetics or steroids; lactation.

Cautious Use

Concomitant use of potassium-depleting diuretics, cardiac disease.

Route & Dosage

Premature Labor
Adult: PO Start 30 min before terminating infusion, 10 mg q2h for first 24 h, then 10–20 mg q4–6h (max: 120 mg/d) IV 50–100 mcg/min, may increase by 50 mcg/min q10min until uterine relaxation is achieved, may continue for up to 12 h after contractions have ceased


Note: IV solution should be clear. Discard if cloudy or a precipitate is present.


PREPARE: IV Infusion: Add 150 mg ritodrine to 500 mL D5W or NS solution to yield 0.3 mg/mL (300 mcg/mL).  

ADMINISTER: IV Infusion: Begin at 50 mcg/min and increase by 50 mcg q10 min until desired response. Monitor IV infusion flow rate to prevent circulation overload. Use a microdrip and infusion pump.  

  • Place patient in left lateral recumbent position throughout the infusion period to reduce risk of hypotension.

Adverse Effects (1%)

Body as a Whole: erythema, nervousness, restlessness, anxiety, malaise, anaphylactic shock , sweating, chills, drowsiness, weakness, myotonic and muscular dystrophies. CNS: Tremor, headache. CV: Altered maternal and fetal heart rates and maternal BP (dose related), palpitations, arrhythmias, chest pain, pulmonary edema. Endocrine: Temporary hyperglycemia. GI: Nausea, vomiting, epigastric distress, ileus, bloating, constipation, diarrhea. Urogenital: Glycosuria. Respiratory: Dyspnea, hyperventilation. Skin: Rash.

Diagnostic Test Interference

Ritodrine (IV route) may produce an increase in serum levels of glucose, insulin, and free fatty acids, and a decrease in serum potassium. It temporarily elevates results of glucose tolerance test.


Drug: corticosteroids may precipitate pulmonary edema; beta agonists add to cardiovascular adverse effects; effects of both ritodrine and beta blockers antagonized.


Absorption: 30% absorbed from GI tract. Peak: 30–60 min. Distribution: Crosses placenta. Metabolism: Metabolized in liver. Elimination: Excreted in urine. Half-Life: 1.7–2.6 h.

Nursing Implications

Assessment & Drug Effects

Patient & Family Education

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug