Ritodrine

Aka: Ritodrine, Yutopar

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II. History

  1. Listed for historical reasons
  2. No longer available in the United States as of 2013
  3. Was the only FDA approved drug for Preterm LaborTocolysis

III. Indications

  1. Preterm Labor

IV. Contraindications

  1. Absolute contraindications
    1. Maternal cardiac disease
    2. Pregnancy Induced Hypertension (PIH)
    3. Uncontrolled Diabetes Mellitus
    4. Hyperthyroidism
    5. Hypovolemia
  2. Relative contraindications
    1. Diabetes Mellitus
    2. Chronic Hypertension
    3. Migraine Headache
    4. Resting Tachycardia
    5. Fever

V. Mechanism

  1. Phenethylamine derivative with beta-2 Adrenergic Agonist activity
  2. Results in Smooth Muscle relaxation (esp. myometrium) and used as a Tocolytic agent
  3. Similar activity to Terbutaline, with intracellular cAMP mediated effects

VI. Dosing: Intravenous

  1. Preparation
    1. Mix Ritodrine 150 mg in 500 ml D5W (0.3 mg/ml)
    2. Results in drip of 50 mcg/minute = 10 ml/hour
  2. Start: 50 mcg per minute
  3. Increase by 50 mcg/minute every 10 minutes until
    1. Contractions cease
    2. Adverse effects limit use
    3. Maximum dosage: 350 mcg per minute
  4. After contractions stop
    1. Reduce by 50 mcg every 30 minutes
    2. Titrate dose to lowest effective Tocolytic dose

VII. Dosing: Oral (Not effective)

  1. Start: 10 mg PO every 2 hours for 24 hours
  2. Next: 10 to 20 mg PO every 4 to 6 hours as needed

VIII. Adverse Effects

  1. Cardiovascular effects (more significant than with Terbutaline)
    1. Maternal Tachycardia
    2. Fetal Tachycardia
    3. Hypotension
  2. Palpitations
  3. Anxiety
  4. Shortness of Breath
  5. Pulmonary Edema
  6. Headache
  7. Nausea or Vomiting
  8. Hypokalemia
  9. Hyperglycemia
  10. Cardiac ischemia

IX. Monitoring

  1. Baseline testing to consider
    1. Electrocardiogram
    2. Serum Glucose
    3. Serum Potassium
    4. Complete Blood Count
    5. Type and screen
  2. Close monitoring
    1. Blood Pressure for Hypertension
    2. Pulse for maternal Tachycardia over 100
    3. Follow Urine Output
    4. Lung Exam for signs of Pulmonary Edema
    5. Follow Serum Glucose and Serum Potassium
    6. Consider fluid restriction <2400 cc per day

X. Efficacy

  1. Not shown to be more effective than Placebo
    1. Does not reduce perinatal mortality or delay labor
    2. (1992) N Engl J Med 327:308-12 [PubMed]

XI. References

  1. Gabbe (2002) Obstetrics p. 787-91
  2. Roberts (1998) Procedures Emergency Medicine p. 993-5

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