PROPRANOLOL HYDROCHLORIDE

Inderal

 Reviewed by Dr Patricia Clarkson, Dr Jon Skinner, Brenda Hughes, Cherry Olsen, Lijla Brkic
November 1999
Administration Newborn Drug Protocol Index Newborn Services Home Page

Dose and Administration

Intravenous
  1. 20 - 100 mcg/kg by slow IV infusion over 10 minutes every 6 hours 4

Oral
  1. 20 -100 mcg/kg/dose 6 hourly 4
  2. Dosage needs to be individualised and will vary depending on both clinical diagnosis and individual patient metabolism.

Indications

  1. Hypoxic spells in Tetralogy of Fallot.
  2. Treatment of neonatal thyrotoxicosis.
  3. Tachyarrhythmia.

Precautions

  1. Use cautiously if there is heart failure.
  2. Use cautiously in heart block.
  3. Use cautiously in renal or hepatic impairment.
  4. Infants with a tendency to bronchospasm.
  5. Bradycardia, hypotension, metabolic acidosis, cardiogenic shock

Drug Interactions

Caffeine An increase in propranolol dose may be required. No clear evidence for this
Chlorpromazine Possible hypotension. (Both drugs inhibit hepatic metabolism of each other)
Digoxin May lead to bradycardia
Insulin Potential for severe, prolonged hypoglycaemia (reported in adult diabetics ).
Phenobarbitone May require increase in propranolol dose. (Increase in metabolism and clearance may occur)
Rifampicin May require increase in propranolol dose. (Increase in hepatic metabolism)
Theophylline Increase in theophylline levels possible
Thyroid hormones Altered levels of triodothyronine, T3 and thyroxine may occur – monitor.
Flecainide Possible additive negative inotropic effect. Cardiac depression may occur
Verapamil Contraindicated in combination with a beta-blocker (negative inotropic effect)

Clinical Pharmacology

Propranolol is a non-selective beta-blocker acting on both β1 (mainly heart) and β2 (bronchial tissue) receptors. Blockade of β2 receptors may result in bronchospasm in some patients. Propranolol has membrane stabilising properties in high doses. It does not have intrinsic sympathomimetic activity (ISA). It exhibits a negative inotropic effect.

Propranolol is almost completely absorbed from the GI tract (adults) and there is significant first pass metabolism and hepatic tissue binding with up to 90% of an oral dose being eliminated. At least one metabolite shows biological activity but the effect on overall activity is unknown. Metabolites and a small amount of unchanged propranolol are excreted in the urine. Propranolol is highly protein-bound (80-95%). It is widely distributed throughout the body with highest levels occurring in the lungs, kidney, brain and heart.

Possible Adverse Effects

  1. Bradycardia.
  2. Hypoglycaemia / hyperglycaemia.
  3. Hypotension in patients with underlying myocardial dysfunction, precipitation of heart failure or heart block
  4. Gastrointestinal effects (diarrhoea, vomiting, constipation)
  5. Thrombocytopenia.
  6. Bronchospasm.

Special Considerations

  1. Monitor: - Blood glucose; Renal, hepatic and haematological studies with prolonged administration.
  2. Have atropine on hand for excessive bradycardia.
  3. Have aminophylline on hand for bronchospasm.
  4. May mask the signs of thyrotoxicosis
  5. Sudden cessation can cause withdrawal (nervousness, tachycardia, sweating, hypertension).