Question

Which PDE 4 inhibitor is used in COPD?

• A. Montelukast
• B. Theophylline
• C. Cromoglicate
• D. Omalizumab

Hint:

Theophylline requires monitoring due to a narrow therapeutic index and potential side effects like tachycardia and nausea.

Answer 1

The Correct Option is B

Theophylline is a methylxanthine drug commonly used in the management of chronic obstructive pulmonary disease (COPD) and asthma. It acts primarily as a phosphodiesterase (PDE) inhibitor, particularly inhibiting PDE-4, leading to an increase in intracellular cyclic AMP (cAMP). This results in relaxation of bronchial smooth muscle and anti-inflammatory effects. Though primarily classified as a nonspecific PDE inhibitor, its PDE-4 inhibitory activity contributes significantly to its bronchodilator and anti-inflammatory effects in COPD. This leads to improved airflow and reduced symptoms in COPD patients. Other options:
- Montelukast is a leukotriene receptor antagonist, not a PDE inhibitor.
- Cromoglicate is a mast cell stabilizer.
- Omalizumab is an anti-IgE monoclonal antibody used mainly in allergic asthma.

Answer 2

The question asks which of the listed drugs works, at least in part, by inhibiting phosphodiesterase type 4 (PDE4) and is used in COPD. Check each drug's actual class and mechanism.

1. Montelukast: This is a leukotriene receptor antagonist that blocks the CysLT1 receptor to reduce bronchoconstriction and inflammation in asthma. It has no phosphodiesterase inhibitory activity, so this option is incorrect.
2. Theophylline: Theophylline is a methylxanthine that, among its several actions, inhibits phosphodiesterase enzymes including PDE4, raising intracellular cyclic AMP in airway smooth muscle and inflammatory cells. This raises cAMP, relaxes bronchial smooth muscle, and adds an anti-inflammatory effect useful in COPD, and it is the option whose mechanism actually includes PDE4 inhibition, so this option is correct.
3. Cromoglicate: Cromoglicate stabilizes mast cell membranes to prevent degranulation and mediator release. It does not act on phosphodiesterase enzymes at all, so this option is incorrect.
4. Omalizumab: Omalizumab is a monoclonal antibody that binds free IgE, used in allergic asthma not well controlled by inhaled therapy. It has no effect on phosphodiesterase, so this option is incorrect.

Of the four, only theophylline's mechanism includes phosphodiesterase inhibition, which covers PDE4 among the isoenzymes it acts on.

Therefore, the correct answer is Theophylline.