Alpha Blockers – Central and Peripheral Acting
Mechanism of Action
Alpha-blockers work by blocking peripheral alpha receptors, thereby decreasing peripheral vascular resistance – causing relaxation and decreased blood pressure. They also relax the smooth muscle in the bladder neck and prostate gland, thus reducing bladder outlet obstruction. Since many of the older men who suffer from hypertension also have prostate enlargement, taking alpha blockers can help with both problems. Centrally acting agents actually work (in the brain) by binding to the same receptors as substances that usually cause an increase in blood pressure and thereby prevents binding of the other substances to result in lowering of blood pressure.
Contraindications to Therapy:
- Allergy to drugs in this class
Side Effects
- Liver toxicity
- Priapism
- Headache
- Arrhythmias
- Raynaud’s disease
- Dizziness
- Low blood pressure
- Congestive heart failure
- Decreased blood cell counts (red, white, and platelets)
- Depression
- Drowsiness
- Lupus erythematosus
Peripheral Alpha Blockers
| Drug | Dosage Regimen | Drug Interactions |
| Doxazosin (Cardura®) |
Oral: Initial:1 mg once daily Maintenance: 1-16 mg once daily |
Verapamil – increased risk of severe lowering in blood pressure |
| Prazosin (Minipress®) |
Oral: Initial not to exceed 1 mg at bedtime Maintenance: 3-20 mg daily (divided 2-3 times daily) |
Verapamil – increased risk of severe lowering in blood pressure |
| Terazosin (Hytrin®) |
Oral: Initial: 1 mg once daily at bedtime Maintenance: 1-5 mg once or twice daily; Maximum: 20-40 mg/day |
Verapamil – increased risk of severe lowering in blood pressure |
Central Alpha Blockers (agonists)
