Question

Which drug used for the treatment of asthma inhibits 5-lipoxygenase? (A) theophylline (B) zileuton (C) zafirlukast (D) fluticasone (E) roflumilast

Short answer

Zileuton (B) is the drug that inhibits 5-lipoxygenase.

Step-by-step solution

Understanding the Question

The question asks us to identify a drug that inhibits 5-lipoxygenase, an enzyme involved in the synthesis of leukotrienes, which are mediators involved in asthma inflammation.

Identifying the Drugs

Examine the options: (A) Theophylline, (B) Zileuton, (C) Zafirlukast, (D) Fluticasone, (E) Roflumilast. Each drug has a specific mechanism of action related to asthma treatment.

Zileuton and 5-lipoxygenase

Recall the mechanism of action for each drug. Zileuton inhibits 5-lipoxygenase. This enzyme converts arachidonic acid to leukotriene A4, a precursor to other leukotrienes associated with airway inflammation in asthma.

Confirming the Answer

Verify the roles of other drugs to ensure they do not inhibit 5-lipoxygenase. Theophylline is a bronchodilator, Zafirlukast is a leukotriene receptor antagonist, Fluticasone is a corticosteroid, and Roflumilast is a phosphodiesterase-4 inhibitor.

Key concepts

Asthma treatment

Asthma is a chronic respiratory condition characterized by inflammation and narrowing of the airways, leading to difficulty in breathing. Treatments aim to reduce inflammation, control symptoms, and enhance the patient's quality of life.

Asthma treatments can be broadly categorized into long-term control medications and quick-relief medications:

• Long-term control medications: These are used daily to maintain control and reduce inflammation over time. They include inhaled corticosteroids, leukotriene modifiers, and long-acting beta-agonists (LABAs).
• Quick-relief medications: Also known as rescue inhalers, these are used to quickly relieve asthma symptoms or an asthma attack. Examples include short-acting beta-agonists (SABAs) and anticholinergics.

Selecting the right medication depends on the severity of the asthma and the individual's specific needs and response to treatment.

5-lipoxygenase inhibitors

The enzyme 5-lipoxygenase plays a crucial role in the inflammatory process related to asthma. It catalyzes the conversion of arachidonic acid into leukotriene A4, a precursor of other leukotrienes responsible for bronchoconstriction.

5-lipoxygenase inhibitors are used in asthma treatment to block this pathway and decrease leukotriene production, thereby reducing inflammation and constriction in the airways.

• These inhibitors provide therapeutic benefits by specifically targeting the enzyme itself.
• They differ from leukotriene receptor antagonists, which block the effects of leukotrienes at their receptor sites.
• By reducing leukotriene synthesis, these compounds serve as preventive strategies rather than acute relief medications.

Leukotriene synthesis

Leukotrienes are inflammatory mediators produced in leukocytes by the oxidation of arachidonic acid. They play a significant role in asthma by contributing to airway edema, smooth muscle contraction, and increased mucus production.

The synthesis process begins with the release of arachidonic acid from the cell membrane, which is then metabolized by 5-lipoxygenase to form leukotriene A4. This unstable intermediate is further processed to form other active leukotrienes such as LTB4, LTC4, LTD4, and LTE4.

• These compounds are involved in the pathophysiology of asthma and contribute to the symptoms experienced by patients.
• Controlling leukotriene synthesis is crucial for managing asthma and improving patient outcomes.
• Inhibition of the leukotriene pathway can effectively reduce bronchoconstriction and inflammation.

Mechanism of action

Mechanism of action refers to how a drug exerts its effects in the body. Understanding this helps identify suitable medications for specific conditions like asthma.

In asthma treatment, mechanisms can include bronchodilation, suppression of inflammation, or preventing leukotriene-mediated effects. Each drug acts differently:

• 5-lipoxygenase inhibitors like Zileuton impede leukotriene synthesis.
• Bronchodilators like Theophylline relax and widen airways.
• Leukotriene receptor antagonists like Zafirlukast block leukotriene receptors, preventing their action.
• Corticosteroids like Fluticasone reduce inflammation significantly by inhibiting inflammatory cells.

Understanding a drug's mechanism is key to prescribing effective asthma treatments based on individual patient needs.

Zileuton

Zileuton is a medication specifically used for asthma treatment due to its ability to inhibit 5-lipoxygenase, an enzyme responsible for initiating leukotriene synthesis. By blocking this enzyme, Zileuton reduces the production of inflammatory leukotrienes, thereby helping to manage asthma symptoms.

Here’s how Zileuton works in asthma management:

• It decreases airway inflammation, leading to less mucus production and smoother breathing.
• It helps prevent bronchoconstriction, thus reducing asthma attacks.
• Zileuton is taken orally and can be part of long-term asthma control therapy.

Patients using Zileuton should be monitored for liver functions, as this medication has potential hepatic side effects. Understanding its role and mechanism is essential for effective asthma control.