1. Clinical Overview
Bilastine is a potent, selective, non-sedating, second-generation H1-antihistamine used for symptomatic relief of allergic conditions. It is a piperidine derivative with high affinity for the human histamine H1 receptor. It is distinguished by its rapid onset of action, long duration, and minimal central nervous system penetration due to being a substrate for the P-glycoprotein efflux transporter. It has no clinically relevant effects on the QT interval.
| Onset | Duration | Bioavailability |
|---|---|---|
| Within 1 hour | 24 hours | Approximately 61% |
2. Mechanism of Action
Bilastine is a potent and selective inverse agonist of the peripheral histamine H1 receptor. It competitively and reversibly binds to the receptor, stabilizing it in its inactive conformation, thereby preventing the intracellular signaling cascade triggered by histamine binding (e.g., Gq protein activation, IP3/DAG production, calcium mobilization). This inhibits the physiological effects of histamine released from mast cells and basophils.
3. Indications & Uses
- Allergic Rhinitis (Seasonal and Perennial)
- Chronic Spontaneous Urticaria (Chronic Idiopathic Urticaria)
4. Dosage & Administration
Adult Dosage: 20 mg once daily.
Administration: Must be taken on an empty stomach. Administer at least 1 hour before or 2 hours after a meal, fruit, or juice (especially grapefruit, orange, apple). Tablet should be swallowed whole with a glass of water.
5. Side Effects
Common side effects may include:
- Headache
- Drowsiness/Somnolence (low incidence)
- Dizziness
- Fatigue
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Ketoconazole, Erythromycin | Increased Bilastine plasma concentration due to P-glycoprotein inhibition. Monitor for increased side effects. | Moderate |
| Grapefruit/Orange/Apple Juice | Marked reduction in Bilastine absorption and AUC by up to 60%. Must be avoided. | Major |
| Alcohol | Additive CNS depressant effect possible, though Bilastine has low sedative potential. Caution advised. | Moderate |
| Other CNS Depressants (e.g., Benzodiazepines, Opioids) | Potential additive sedation. | Moderate |
| Anticholinergic drugs | Theoretical additive anticholinergic effects, though Bilastine has low affinity. | Low |
7. Patient Counselling
- DO take the tablet on an empty stomach (1 hr before or 2 hrs after food/juice).
- DO swallow the tablet whole with water.
- DO inform your doctor about all other medicines you are taking.
- DO NOT crush or chew the tablet.
- DO NOT take with grapefruit, orange, or apple juice.
- DO NOT exceed the prescribed dose of one tablet per day.
8. Toxicology & Storage
Overdose: Expected to be an extension of pharmacological effects: drowsiness, dizziness, headache, possible gastrointestinal discomfort. No specific life-threatening symptoms reported in overdose.
Storage: Store below 30°C. Protect from light and moisture. Keep out of reach of children.