Usage
Guaifenesin + Terbutaline is prescribed for the symptomatic relief of productive cough associated with bronchospasm in conditions like asthma, bronchitis, chronic obstructive pulmonary disease (COPD), bronchiectasis, and emphysema. It combines an expectorant (guaifenesin) and a bronchodilator (terbutaline).
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Pharmacological Classification: Expectorant and Bronchodilator (Beta-2 adrenergic agonist).
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Mechanism of Action: Guaifenesin increases respiratory tract fluid secretions, reducing mucus viscosity and facilitating expectoration. Terbutaline relaxes bronchial smooth muscle by stimulating beta-2 adrenergic receptors, thereby dilating the airways and relieving bronchospasm.
Alternate Names
There are no widely recognized alternate names for the combination itself. However, the individual components have other names:
- Guaifenesin: glycerol guaiacolate
- Terbutaline: Bricanyl, Brethine
How It Works
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Pharmacodynamics: Guaifenesin increases the volume and reduces the viscosity of respiratory secretions, making it easier to cough up phlegm. Terbutaline relaxes bronchial smooth muscle, leading to bronchodilation and improved airflow.
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Pharmacokinetics:
- Guaifenesin: Rapidly absorbed after oral administration, metabolized in the liver, and excreted in the urine.
- Terbutaline: Absorbed orally and subcutaneously. Metabolized primarily by conjugation and excreted in the urine.
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Mode of Action: Terbutaline binds to beta-2 adrenergic receptors on bronchial smooth muscle cells, activating intracellular signaling pathways that lead to smooth muscle relaxation and bronchodilation. Guaifenesin’s exact mode of action is not fully understood but involves increasing respiratory tract fluid secretions.
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Elimination Pathways: Guaifenesin is metabolized in the liver and excreted in the urine. Terbutaline is primarily conjugated and eliminated in the urine.
Dosage
Standard Dosage
Children:
- 2-4 years: 2.5 ml two to three times a day.
- 4-6 years: 5 ml two to three times a day.
- 6-12 years: 5-10 ml two to three times a day.
- >12 years: 10 ml three times a day.
Dosing should always be adjusted based on the specific product formulation and the child’s weight and age, adhering to the recommended maximum daily dose of terbutaline.
Special Cases:
- Elderly Patients: Start with a lower dose and adjust as needed, monitoring for adverse effects.
- Patients with Renal Impairment: Use with caution; dose adjustment may be necessary.
- Patients with Hepatic Dysfunction: Use with caution; dose adjustment may be necessary.
- Patients with Comorbid Conditions: Use with caution in patients with diabetes, cardiovascular disease, hypertension, hyperthyroidism.
Clinical Use Cases
This combination is not typically used in clinical settings like intubation, surgical procedures, mechanical ventilation, or the ICU. It is primarily intended for outpatient management of cough and bronchospasm.
Dosage Adjustments
Dose adjustments are required for renal and hepatic impairment, elderly patients, and those with certain comorbid conditions. Dosage modifications must always consider the individual components of the combination and their respective pharmacokinetic profiles.
Side Effects
Common Side Effects:
- Tremor
- Nervousness
- Headache
- Tachycardia
- Nausea
- Vomiting
- Dizziness
Rare but Serious Side Effects:
- Cardiac arrhythmias
- Hypokalemia
- Hypersensitivity reactions
Long-Term Effects:
No specific long-term adverse effects have been directly attributed to this combination.
Adverse Drug Reactions (ADR):
Clinically significant ADRs include severe allergic reactions (anaphylaxis, angioedema), significant cardiac arrhythmias, and severe hypokalemia.
Contraindications
- Hypersensitivity to any component of the formulation
- Ischemic heart disease
- Significant risk factors for ischemic heart disease
- Thyrotoxicosis
Drug Interactions
- Beta-blockers (may antagonize the bronchodilating effects of terbutaline)
- MAO inhibitors, tricyclic antidepressants (may potentiate the cardiovascular effects of terbutaline)
- Xanthines, corticosteroids, diuretics (may exacerbate hypokalemia caused by terbutaline)
- Digitalis glycosides (hypokalemia from terbutaline may increase the risk of arrhythmias)
- Sympathomimetic bronchodilators (additive cardiovascular effects)
Pregnancy and Breastfeeding
Terbutaline should not be used for tocolysis. Safety during pregnancy and breastfeeding has not been fully established. It is advisable to weigh the potential benefits against the potential risks. Consult with a specialist.
Drug Profile Summary
- Mechanism of Action: Guaifenesin loosens mucus; terbutaline dilates bronchi.
- Side Effects: Tremor, nervousness, headache, tachycardia, nausea, vomiting.
- Contraindications: Hypersensitivity, heart disease, thyrotoxicosis.
- Drug Interactions: Beta-blockers, MAO inhibitors, tricyclic antidepressants, xanthines.
- Pregnancy & Breastfeeding: Use with caution.
- Dosage: As described in the dosage section.
- Monitoring Parameters: Respiratory rate, heart rate, blood pressure, potassium levels.
Popular Combinations
This particular combination is itself a popular combination. Terbutaline may be combined with other expectorants or mucolytics.
Precautions
Assess for allergies, metabolic disorders, and organ dysfunction before initiating therapy. Use with caution in pregnant or breastfeeding women, children, and the elderly. Alcohol may enhance side effects. Patients should avoid operating machinery if dizziness occurs.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Guaifenesin + Terbutaline?
A: See detailed dosage guidelines above.
Q2: What are the common side effects?
A: Common side effects include tremor, nervousness, headache, tachycardia, nausea, and vomiting.
Q3: Is it safe in pregnancy?
A: Terbutaline should not be used for tocolysis. Use with caution during pregnancy; consult a specialist.
Q4: What are the contraindications?
A: Contraindications include hypersensitivity, ischemic heart disease, and thyrotoxicosis.
Q5: How does Guaifenesin work?
A: Guaifenesin thins and loosens mucus, making it easier to cough up.
Q6: How does Terbutaline work?
A: Terbutaline relaxes bronchial smooth muscle, leading to bronchodilation.
Q7: Can it be used in children?
A: Yes, with appropriate dose adjustments based on age and weight. Refer to the dosage section.
Q8: What should I monitor in patients taking this combination?
A: Monitor respiratory rate, heart rate, blood pressure, and potassium levels.
Q9: What are the significant drug interactions?
A: Significant drug interactions include beta-blockers, MAO inhibitors, and tricyclic antidepressants.
