Usage
Orciprenaline is prescribed for the relief of bronchospasm associated with chronic obstructive pulmonary disease (COPD), including chronic bronchitis, emphysema, and asthma. It is also used in the treatment of reversible bronchospasm associated with bronchitis and emphysema. It is classified as a bronchodilator, specifically a β₂-adrenergic agonist. Its mechanism of action involves stimulating β₂-adrenergic receptors in the lungs, leading to relaxation of bronchial smooth muscle and bronchodilation.
Alternate Names
The alternate name for Orciprenaline is Metaproterenol. Brand names include Alupent and Orciprenaline Sulphate Syrup.
How It Works
Pharmacodynamics: Orciprenaline acts as a β₂-adrenergic receptor agonist. Upon binding to these receptors, it activates adenylate cyclase, which increases intracellular cyclic adenosine monophosphate (cAMP). This increase in cAMP leads to relaxation of bronchial smooth muscle, resulting in bronchodilation. Orciprenaline also inhibits the release of mediators of immediate hypersensitivity reactions from mast cells.
Pharmacokinetics:
- Absorption: Orciprenaline is well-absorbed from the gastrointestinal tract after oral administration.
- Metabolism: It undergoes extensive first-pass metabolism in the liver, which reduces its bioavailability to approximately 40%.
- Elimination: Orciprenaline is primarily excreted in the urine as glucuronic acid conjugates. It has a biphasic elimination pattern, with an initial rapid distribution phase and a slower terminal elimination half-life of approximately 15 hours.
Mode of Action: Orciprenaline binds to β₂-adrenergic receptors on bronchial smooth muscle cells, initiating a cascade that increases cAMP levels and ultimately relaxes the muscle.
Receptor Binding: Orciprenaline selectively binds to β₂-adrenergic receptors.
Elimination Pathways: Primarily renal excretion as glucuronic acid conjugates following hepatic metabolism.
Dosage
Standard Dosage
Adults:
20 mg three or four times daily. The maximum recommended daily dose is 120 mg.
Children:
- 4-12 years: 10 mg three times daily.
- >12 years: 20 mg three times daily.
Special Cases:
- Elderly Patients: Start with lower doses and titrate upwards carefully monitoring for adverse effects.
- Patients with Renal Impairment: Dose adjustment may be necessary. Monitor renal function closely.
- Patients with Hepatic Dysfunction: Dose reduction may be required due to potential decreased metabolism. Close monitoring is recommended.
- Patients with Comorbid Conditions: Use with caution in patients with hypertension, coronary artery disease, congestive heart failure, diabetes mellitus, hyperthyroidism, glaucoma, or those sensitive to sympathomimetic amines. Monitor carefully.
Clinical Use Cases
Orciprenaline is primarily used for the long-term management of chronic conditions like asthma, bronchitis and emphysema rather than acute settings. Hence specific dosages for intubation, surgical procedures, mechanical ventilation, ICU use, and emergency situations are not generally established. It is crucial to note that Orciprenaline’s role in acute asthma management is limited.
Dosage Adjustments
Dose adjustments should be based on patient response and tolerance. Monitor for side effects, especially in patients with comorbid conditions. Renal and hepatic function should be considered when adjusting dosage.
Side Effects
Common Side Effects
Tremor, palpitations, tachycardia, nervousness, headache, dizziness, nausea, and diarrhea.
Rare but Serious Side Effects
Hypersensitivity reactions (e.g., urticaria, angioedema, bronchospasm), paradoxical bronchospasm, hypokalemia, cardiac arrhythmias, and worsening of pre-existing cardiovascular conditions.
Long-Term Effects
Tolerance to the bronchodilator effect may develop with prolonged use. Chronic use without concomitant anti-inflammatory therapy may worsen asthma control.
Adverse Drug Reactions (ADR)
Severe allergic reactions, significant changes in blood pressure, and severe cardiac arrhythmias.
Contraindications
Hypersensitivity to orciprenaline or any component of the formulation; hypertrophic obstructive cardiomyopathy; cardiac arrhythmias associated with tachycardia; concomitant use with beta-blockers (except in overdose management).
Drug Interactions
Other sympathomimetic agents, monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), beta-blockers, and xanthine derivatives. May potentiate hypokalemia induced by diuretics and steroids.
Pregnancy and Breastfeeding
Pregnancy Safety Category C. Use with caution during pregnancy, weighing potential benefits against fetal risks. Use cautiously during breastfeeding due to the potential for drug excretion in breast milk and neonatal side effects.
Drug Profile Summary
- Mechanism of Action: β₂-adrenergic agonist, relaxes bronchial smooth muscle.
- Side Effects: Tremor, palpitations, tachycardia, nervousness, headache, dizziness, nausea, diarrhea. Rare but serious: hypersensitivity reactions, paradoxical bronchospasm, hypokalemia, cardiac arrhythmias.
- Contraindications: Hypersensitivity, hypertrophic obstructive cardiomyopathy, tachycardia-associated arrhythmias, concomitant beta-blocker use.
- Drug Interactions: Sympathomimetics, MAOIs, TCAs, beta-blockers, xanthines, diuretics, steroids.
- Pregnancy & Breastfeeding: Category C; use with caution.
- Dosage: Adults: 20 mg TID/QID (max 120 mg/day); Children (4-12 yrs): 10 mg TID; Children (>12 yrs): 20 mg TID.
- Monitoring Parameters: Pulmonary function tests (FEV₁, peak flow), heart rate, blood pressure, serum potassium, blood glucose, CNS stimulation.
Popular Combinations
Orciprenaline is sometimes combined with inhaled corticosteroids for long-term asthma management.
Precautions
Close monitoring is necessary in patients with cardiovascular disease, diabetes, glaucoma, hypokalemia, or seizures. Avoid long-term daily use for acute asthma. Monitor potassium levels in patients receiving concomitant xanthine derivatives, steroids, or diuretics.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Orciprenaline?
A: Adults: 20 mg three or four times daily (max 120 mg/day). Children (4-12 years): 10 mg three times daily. Children (>12 years): 20 mg three times daily.
Q2: How does Orciprenaline work?
A: It stimulates β₂-adrenergic receptors causing bronchial smooth muscle relaxation and bronchodilation.
Q3: What are the common side effects of Orciprenaline?
A: Tremor, palpitations, tachycardia, nervousness, headache, dizziness, nausea, and diarrhea.
Q4: What are the contraindications for Orciprenaline?
A: Hypersensitivity, hypertrophic obstructive cardiomyopathy, tachycardia-associated arrhythmias, and concomitant use with beta-blockers.
Q5: Can Orciprenaline be used during pregnancy?
A: It’s a Pregnancy Category C drug. Use with caution, weighing the benefits against potential risks to the fetus.
Q6: Does Orciprenaline interact with other medications?
A: Yes, it interacts with other sympathomimetics, MAOIs, TCAs, beta-blockers, xanthine derivatives, diuretics, and steroids.
Q7: What should be monitored in patients taking Orciprenaline?
A: Pulmonary function tests (FEV₁, peak flow), heart rate, blood pressure, serum potassium, and blood glucose levels.
Q8: Can Orciprenaline be used in patients with renal or hepatic impairment?
A: Use with caution. Dosage adjustments and close monitoring are necessary.
Q9: What is the difference between Orciprenaline and Salbutamol?
A: Both are β₂-agonists, but Salbutamol is shorter-acting and more commonly used for acute relief of bronchospasm, while Orciprenaline is longer-acting and preferred for maintenance therapy.
Q10: How long does the effect of Orciprenaline last?
A: The bronchodilator effect typically lasts for 3 to 6 hours.
