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Drug dosage identifier

Isoprenaline hydrochloride

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Dose and administration

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50-500 nanograms/kg/min (0.05-0.5 mcg/kg/min) by continuous IV infusion.

Isoprenaline (mg) in 50ml IV solution = 3 x weight (kg) x dose (mcg/kg/min)
                                                                            IV rate (ml/hr)

Indications

Contraindications and precautions

  • Known hypersensitivity to isoprenaline.
  • Hypovolaemia.

Clinical pharmacology

Isoprenaline hydrochloride is a synthetic sympathomimetic amine that is structurally related to adrenaline. The drug is a B1 and B2 adrenergic agonist with almost no activity on a receptors. Increases cardiac output by increasing heart rate, contractility and venous return. Lowers peripheral vascular resistance. Relaxes most smooth muscles, especially bronchial and gastrointestinal. Decreases pulmonary artery pressure and pulmonary artery resistance in experimental animals. Stimulates insulin secretion. Metabolised in the liver and other tissues by catechol-o-methyl transferase. Marked chronotropic and arrhythmogenic effects. May cause myocardial ischaemia or necrosis.

Possible adverse effects

  • Hypotension
  • Arrhythmias
  • Decreased perfusion to kidney, heart, brain.
  • Tremors, irritability.
  • Gastrointestinal disturbances (nausea, vomiting and diarrhoea).
  • Myocardial necrosis.

Special considerations

  • Titrate infusion rate according to clinical response and/or side effects. May increase dose every 2-3 minutes until appropriate response obtained.
  • Hypovolaemia, metabolic acidosis should be corrected before infusion commences.
  • Simultaneous administration with adrenaline may lead to serious arrhythmias.

Management of Isoprenaline administration

Description

  • Clear, colourless solution 1:5000 (0.2 mg/ml [200micrograms/ml] in 1 ml ampoules).
  • Contains benzyl alcohol.

Prescription

Charted on fluid chart giving:

  • rate in ml/hour
  • dose in nanograms/kg/minute

Also charted on drug chart under continuous infusions giving:

  • amount of drug to be added
  • base fluid, type and volume
  • nanograms/kg/ml

Administration

Continuous Infusion

  1. Dilute prior to administration.
  2. Filter prior to administration through a 5 micron filter.
  3. Compatible with D5W, D10W, NS. Is compatible with furosemide and sodium bicarbonate.
  4. Do NOT mix with other drugs, IV solutions, blood or blood products.
  5. Discard any discoloured solution.
  6. Administer via a syringe pump.
  7. Cover tubing and syringe with tinfoil.
  8. Stability of diluted isoprenaline solutions unknown. Change solution and tubing every 24 hours. Consider more frequent solution change if baby's clinical condition is deteriorating (solution may be losing potency).

Observation and documentation

  1. Assess for signs of adverse effects.
  2. Continuous cardiorespiratory monitoring.
  3. Continuous blood pressure monitoring.
  4. Monitor central venous pressure.
  5. Document vital signs hourly and PRN.
  6. Obtain blood gases before and during drug use.
  7. Monitor both an upper and a lower TcO2, and pulse oximetry.
  8. Monitor fluid balance.

Storage

  • Unopened. Store in refrigerator at 2-8°C. Do NOT freeze.
  • Discard ampoule after use.
  • Continuous infusion. Change solution and tubing every 24 hours.

Selected references

  1. Cabal LA, Devaskar U, Siassi V, et al. Cardiogenic shock associated with perinatal asphyxia in preterm infants. J Pediatr 1980; 96:705.
  2. Daoud FS, Reeves JT, Kelly DB. Isoproterenol as a potential pulmonary vasodilator in primary pulmonary hypertension. Am J Cardiol 1978; 42:817.

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Document Control

  • Date last published: 30 April 2003
  • Document type: Drug Dosage Guideline
  • Services responsible: ADHB Pharmacy, Neonatology
  • Editor: Sarah Bellhouse
  • Review frequency: 2 years