Review of Pharmacology - 9E (2015)

Respiratory System
Explanations
1. Ans. (b) Terbutaline (Ref: Katzung 12/e p344)
All four drugs i.e. albuterol (salbutamol), terbutaline, metaproterenol and pirbuterol are available as metered dose inhaler
Salbutamol and terbutaline are also available in tablet forms
Only terbutaline is available as subcutaneous injection. This route is indicated only for severe asthma requiring emergency
treatment when aerosolized therapy is not available or has been ineffective.
2. Ans. (a) Phosphodiesterase 4 inhibition (Ref: Katzung 11/e p345)
Theophylline is used in bronchial asthma. Its mechanism of action is:
• Inhibition of phosphodiesterases particularly PDE-4.
• Antagonism of adenosine receptors.
• Enhancement of histone deacetylation. Acetylation of histone is required for activation of inflammatory gene transcription.
By inhibiting this process, low-dose theophylline may restore responsiveness to corticosteroids.
3. Ans. (a) Sodium cromoglycate (Ref: Katzung 10/e p325; KDT 6/e p223)
Mast cell stabilizers like cromoglycate and nedocromil are used to prevent exercise induced asthma. However, corticosteroids
are preferred for this indication.
4. Ans. (a) Magnesium sulphate (Ref: Harrison 17/e p1605)
Magnesium sulphate by i.v. or inhalational route has been used for the treatment of acute severe asthma. All other drugs
mentioned in the options are used for prophylaxis of asthma.
5. Ans. (a) Zafirlukast (Ref: KDT 6/e p222-223)
• Montelukast, zafirlukast and idalukast are Cys-LT 1
receptor antagonists.
• Zileuton inhibits the production of leukotrienes by inhibiting the enzyme 5-lipoxygenase.
6. Ans. (c) Phosphodiesterase (Ref: KDT 6/e p220)
7. Ans. (c) Adenosine receptors (Ref: KDT 6/e p220)
8. Ans. (a) Increase in dose is required in cardiopulmonary disease (Ref: KDT 6/e p220, 221)
• Theophylline is a methylxanthine derivative. It acts by inhibiting the metabolism of cAMP through inhibition of the
enzymes, phosphodiesterase-III and IV. Resulting increase in cAMP is responsible for bronchodilation.
Dose reduction is required in
• Elderly • Smokers
• Patients with CHF • Children
Dose should be increased in
• Patients of pneumonia • Concomitant administration of enzyme inducers like
rifampicin and phenobarbitone
• Hepatic insufficiency
• With enzyme inhibitors like ciprofloxacin, cimetidine
and erythromycin
General Respiratory Pharmacology System
9. Ans. (d) 5-6 mg/kg (Ref: KDT 6/e p221)
Aminophylline is administered in a dose of 5-7 mg/kg slow intravenous influsion. In children, dose required is
7.5 mg/kg.
10. Ans. (d) Hypoglycemia (Ref: KDT 6/e p127)
β 2
agonists like salbutamol and terbutaline can cause several adverse effects like:
• Tachycardia due to stimulation of chronotropic β 2
receptors and at high dose due to stimulation of β 1
receptors
also.
• Tremors may result due to stimulation of muscle spindles.
• Tolerance may develop due to densensitization of receptors.
• Transient hyperkalemia followed by prolonged hypokalemia is seen on continued use.
• Hyperglycemia may develop due to release of glucagon and stimulation of glycogenolysis and gluconeogenesis.
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