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Isoprenaline: Uses, Dosage, Side Effects & Mechanism | DrugsAtlas

Authoritative Clinical Reference

DRUG NAME: Isoprenaline

Therapeutic Class: Sympathomimetic

Subclass: Non-selective β-adrenergic agonist

Speciality: Cardiology

Schedule (India): Schedule H

Route(s): Intravenous (IV), Intramuscular (IM), Subcutaneous (SC)

Formulations Available in India:

• Isoprenaline injection: 1 mg/mL in 2 mL ampoule
• Isoprenaline injection: 0.2 mg/mL in 1 mL ampoule

INDICATIONS + DOSING — FOR CLINICIAN USE ONLY

Primary Indications (Approved / Standard in India)

1. Symptomatic Bradyarrhythmias (including complete heart block) — Emergency/Bridge Therapy

Intravenous Infusion (Preferred Route):

Parameter	Recommendation
Starting dose	0.5–1 mcg/min IV infusion (approximately 0.01 mcg/kg/min)
Titration	Increase by 0.5–1 mcg/min every 10–15 minutes based on heart rate and BP response
Usual maintenance dose	2–10 mcg/min (0.02–0.1 mcg/kg/min)
Maximum dose	20 mcg/min (approximately 0.2 mcg/kg/min) in refractory cases

Intramuscular/Subcutaneous (Alternate when IV not feasible):

Parameter	Recommendation
Starting dose	0.2 mg IM or SC
Titration	May repeat after 2–4 hours if required based on clinical response
Usual maintenance dose	0.2–0.4 mg per dose
Maximum dose	1 mg per single dose

Clinical Notes:
→ Temporary measure only — definitive therapy is cardiac pacing
→ Continuous ECG monitoring mandatory throughout infusion
→ Correct hypovolaemia and electrolyte abnormalities before initiation
→ Dilute IV preparation in 5% dextrose or 0.9% saline before infusion
→ Never administer undiluted IV bolus — risk of fatal arrhythmias

2. Acute Severe Bronchospasm (Historical/Limited Use)

Parameter	Recommendation
Starting dose	0.1–0.2 mg SC or IM
Titration	Not applicable
Usual maintenance dose	0.1–0.2 mg every 4–6 hours
Maximum dose	0.4 mg per dose; duration ≤24 hours

Clinical Notes:
→ Reserved only when selective β2-agonists (salbutamol, terbutaline) are unavailable
→ Higher cardiac adverse effect profile than selective agents
→ Not recommended as first-line bronchodilator

Secondary Indications – Adults (Off-label, if any)

1. Post-Cardiac Transplant Bradycardia (OFF-LABEL)
• Dose: 0.5–2 mcg/min IV infusion; titrate to target heart rate 80–100 bpm
• Duration: Short-term bridge until chronotropic response recovers or pacemaker placed
• Specialist only: Cardiac transplant units
• Evidence basis: Standard practice in cardiac transplant centres; institutional protocols

2. Torsades de Pointes (Drug-Induced or Pause-Dependent) (OFF-LABEL)
• Dose: 2–10 mcg/min IV infusion to increase heart rate >90 bpm
• Duration: Until causative agent cleared or temporary pacing established
• Specialist only: CCU/electrophysiology setting
• Evidence basis: Established electrophysiology practice; shortens QT interval by increasing heart rate

PAEDIATRIC DOSING (Specialist Only)

Primary Indications (Approved / Standard in India)

Symptomatic Bradycardia / Complete Heart Block — Emergency/Bridge to Pacing

Parameter	Recommendation
Starting dose	0.05 mcg/kg/min IV continuous infusion
Titration	Increase by 0.05 mcg/kg/min every 10–15 minutes based on heart rate response
Usual maintenance dose	0.1–0.2 mcg/kg/min
Maximum dose	0.5 mcg/kg/min

Alternative Route (IM/SC) — when IV access not available:

Parameter	Recommendation
Starting dose	0.01 mg/kg (10 mcg/kg) IM or SC
Titration	May repeat after 4–6 hours if necessary
Usual maintenance dose	Individualised based on response
Maximum dose	0.25 mg per single dose

Clinical Notes:
→ Continuous ECG and BP monitoring mandatory
→ Specialist paediatric cardiology or PICU supervision required
→ Minimum age: May be used in neonates under specialist supervision
→ Correct hypokalaemia and acidosis before or during therapy
→ Prepare for emergency temporary pacing if available

Secondary Indications – Paediatric doses (Off-label, if any)

• Not routinely established in paediatric practice
• Any off-label use requires paediatric cardiology specialist input
• Use in neonates only under specialist supervision in tertiary centres with pacing capability

RENAL ADJUSTMENT

• No specific dose adjustment required
• Use with caution in severe renal impairment — increased susceptibility to arrhythmias due to electrolyte disturbances
• Monitor serum potassium closely

HEPATIC ADJUSTMENT

Severity (Child-Pugh)	Recommendation
Class A (Mild)	No dose adjustment required
Class B (Moderate)	Use with caution; drug may accumulate due to reduced hepatic metabolism
Class C (Severe)	Specialist use only; initiate at lower dose with slower titration; close ECG monitoring

CONTRAINDICATIONS

• Tachyarrhythmias (ventricular tachycardia, ventricular fibrillation, supraventricular tachycardia)
• Phaeochromocytoma — risk of severe hypertensive crisis
• Known hypersensitivity to isoprenaline or any excipient
• Digitalis toxicity with arrhythmias
• Concurrent use with MAO inhibitors (within 14 days)
• Uncorrected hypovolaemia

CAUTIONS

• Coronary artery disease — increased myocardial oxygen demand may precipitate ischaemia
• Hypertrophic obstructive cardiomyopathy — may worsen outflow obstruction
• Hyperthyroidism — enhanced sensitivity to catecholamines
• Diabetes mellitus — may cause transient hyperglycaemia
• Hypokalaemia — increases arrhythmia risk; correct before or during therapy
• Elderly patients — increased cardiac sensitivity
• Patients receiving volatile anaesthetics — enhanced arrhythmogenic potential

PREGNANCY

Parameter	Guidance
Overall safety	Limited human data; use only when clearly indicated and alternatives ineffective
When permissible	Severe bradyarrhythmia unresponsive to atropine; life-threatening situation
Preferred alternatives	Atropine for bradycardia; transcutaneous pacing if available
Monitoring	Continuous maternal ECG and BP; fetal heart rate monitoring; avoid prolonged use

LACTATION

Parameter	Guidance
Breastfeeding compatibility	Unknown; likely minimal transfer due to short half-life
Milk levels	Expected to be low
Preferred alternatives	Avoid if possible; use only in emergency settings
Infant monitoring	If unavoidable, observe infant for tachycardia, irritability, poor feeding

ELDERLY

• Starting dose: Use lower end of range (0.5 mcg/min IV or 0.1 mg IM/SC)
• Titration: Slower increments with extended observation intervals (every 20–30 minutes)
• Increased risks:

Enhanced sensitivity to chronotropic and inotropic effects
Higher incidence of arrhythmias including ventricular ectopy
Risk of myocardial ischaemia or infarction
Falls risk post-therapy due to postural hypotension
• Continuous ECG monitoring essential
• Avoid prolonged use

MAJOR DRUG INTERACTIONS

Interacting Drug	Effect	Management
MAO inhibitors (phenelzine, tranylcypromine, selegiline)	Severe potentiation of sympathomimetic effects; hypertensive crisis; fatal arrhythmias	CONTRAINDICATED — avoid within 14 days of MAOI use
Digitalis glycosides (digoxin)	Synergistic arrhythmogenic effect; risk of ventricular arrhythmias especially with hypokalaemia	AVOID concurrent use; if essential, intensive ECG monitoring
Halogenated anaesthetics (halothane, sevoflurane)	Sensitise myocardium to catecholamines; increased arrhythmia risk	Avoid or use minimal doses; inform anaesthetist
Non-selective β-blockers (propranolol)	Antagonise bronchodilator effect; may cause paradoxical bronchospasm	Avoid combination

MODERATE DRUG INTERACTIONS

Interacting Drug	Effect	Management
Tricyclic antidepressants (amitriptyline, imipramine)	Enhanced cardiovascular effects; increased arrhythmia risk	Use with caution; monitor ECG and heart rate
Loop diuretics (furosemide)	Additive hypokalaemia → increased arrhythmia susceptibility	Monitor serum potassium; replete if low
Thiazide diuretics	Additive hypokalaemia	Monitor electrolytes
Theophylline	Additive cardiac stimulation; hypokalaemia	Monitor heart rate and potassium levels
Corticosteroids (systemic)	May potentiate hypokalaemic effect	Monitor serum potassium
Sympathomimetics (adrenaline, dopamine)	Additive cardiovascular stimulation; increased arrhythmia risk	Use together only with close monitoring in ICU setting

COMMON ADVERSE EFFECTS

• Palpitations
• Tachycardia
• Headache
• Flushing
• Tremor
• Nervousness or restlessness
• Nausea
• Dizziness

SERIOUS ADVERSE EFFECTS

• Ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation) — discontinue immediately; initiate resuscitation if needed
• Myocardial ischaemia or infarction — particularly in patients with underlying coronary artery disease
• Severe hypotension — due to peripheral β2-mediated vasodilation at high doses
• Pulmonary oedema — rare; may occur with prolonged high-dose infusion
• Sudden cardiac death — associated with IV bolus administration or overdose
• Severe hypokalaemia — may precipitate life-threatening arrhythmias

MONITORING REQUIREMENTS

Baseline:
• 12-lead ECG
• Serum electrolytes (particularly potassium and magnesium)
• Blood pressure
• Heart rate
• Cardiac history review (rule out ischaemic heart disease, structural abnormalities)

During Therapy:
• Continuous ECG monitoring (mandatory)
• Heart rate every 5–10 minutes during titration
• Blood pressure every 10–15 minutes
• Urine output monitoring
• Serum potassium every 6–12 hours for prolonged infusions
• Watch for chest pain or new ST-T changes

Post-Infusion:
• ECG to assess for residual arrhythmias
• Monitor for rebound bradycardia
• Reassess need for permanent pacing

BRANDS AVAILABLE IN INDIA

• Isuprel (Abbott)
• Isopren (Samarth Pharma)
• Other institutional/generic preparations in select tertiary hospitals

PRICE RANGE (INR)

• ₹40–₹80 per ampoule (1–2 mL)
• NLEM status: Not included
• Availability: Primarily in tertiary care centres, emergency departments, and cardiac care units
• Government supply: Limited; available in select emergency drug kits

CLINICAL PEARLS

• Temporary bridge therapy only — always plan for definitive pacing in complete heart block
• Atropine is first-line for bradycardia; isoprenaline reserved when atropine fails or is contraindicated
• Never give undiluted IV bolus — dilute and infuse slowly to prevent fatal arrhythmias
• Tachyphylaxis develops rapidly with prolonged infusion — effectiveness diminishes after 24–48 hours
• Correct hypokalaemia before or during therapy to minimise arrhythmia risk
• Avoid in atrial fibrillation with accessory pathways (WPW syndrome) — may accelerate ventricular response
• Keep emergency resuscitation equipment available during infusion

Clinical Responsibility

This platform is designed strictly for healthcare professionals. Data provided is synthesized from authoritative pharmacological sources and clinical registries. Do not use for consumer medical decisions. Always verify critical dosing and contraindications with official institutional protocols and peer-reviewed journals.

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