Terazosin is a versatile alpha-blocker prescribed for men with benign prostatic hyperplasia (BPH) to improve urine flow and for both men and women to manage high blood pressure. While effective, its primary mechanism of action—relaxing blood vessels—means it can cause a significant drop in blood pressure, especially when combined with other substances that have a similar effect. Understanding these potential interactions is critical for patient safety.
The Primary Concern: Additive Hypotensive Effects
Terazosin works by blocking alpha-1 adrenergic receptors, which relaxes smooth muscles in the prostate and bladder neck, and in the walls of arteries and veins. This vasodilation effect is what lowers blood pressure and relieves BPH symptoms. The most significant danger arises when terazosin is taken with other drugs that also lower blood pressure, leading to an additive or synergistic effect. This can cause severe hypotension, resulting in symptoms like dizziness, lightheadedness, and fainting, especially when standing up too quickly.
Key Drugs to Avoid or Use with Extreme Caution
PDE-5 Inhibitors (Erectile Dysfunction Drugs)
Phosphodiesterase type 5 (PDE-5) inhibitors are a class of drugs used to treat erectile dysfunction (ED). When combined with terazosin, the risk of a severe drop in blood pressure is significantly increased due to the additive vasodilatory effects. This interaction can lead to dizziness, fainting, headache, and flushing. It is generally recommended to use these medications with great caution, if at all, and to ensure stable dosing of one medication before starting the other.
Examples include:
- Sildenafil (Viagra, Revatio)
- Tadalafil (Cialis)
- Vardenafil (Levitra, Staxyn)
- Avanafil (Stendra)
Other Alpha-Blockers
Combining multiple alpha-blockers is generally contraindicated. Taking terazosin with another alpha-blocker can lead to an additive effect that substantially increases the risk of hypotension. Using these medications together does not provide a greater therapeutic benefit and unnecessarily elevates the risk of adverse effects.
Examples include:
- Tamsulosin (Flomax)
- Doxazosin (Cardura)
- Prazosin (Minipress)
- Alfuzosin (Uroxatral)
- Silodosin (Rapaflo)
Other Blood Pressure Medications
Terazosin's blood pressure-lowering effect can be dangerously amplified when used with other antihypertensive agents. A particular concern exists with the calcium channel blocker verapamil, which has been shown to cause a significant drop in blood pressure and fainting when co-administered with terazosin. Other classes of antihypertensives, such as beta-blockers and diuretics, may also need careful dose monitoring.
High-Dose Pain and Psychotropic Medications
Certain drugs used for pain or mental health can increase the risk of hypotension when combined with terazosin. High doses of some nonsteroidal anti-inflammatory drugs (NSAIDs) may antagonize terazosin's blood pressure-lowering effects. Conversely, some antidepressants, including tricyclics like amitriptyline and certain antipsychotics, can have additive hypotensive effects.
Lifestyle and Substance Interactions
Alcohol
Consuming alcohol while on terazosin can significantly increase the risk and severity of hypotension, dizziness, and fainting. Alcohol's vasodilatory properties compound the effect of terazosin. Patients should be advised to avoid alcohol or limit their intake, especially when first starting the medication or after a dosage increase.
Herbal Supplements
Some herbal products can also interfere with terazosin. Yohimbe is known to increase the hypotensive effects of alpha-blockers and is generally contraindicated for use with terazosin. Always inform your healthcare provider about any herbal supplements you are taking, as they can have potent pharmacological effects.
Comparison of Key Terazosin Interactions
| Drug Class | Examples | Interaction Risk | Management Recommendation |
|---|---|---|---|
| PDE-5 Inhibitors | Sildenafil, Tadalafil, Vardenafil | Significant risk of severe hypotension, dizziness, and fainting. | Avoid or use with extreme caution. Ensure stable dosing of one medication before starting the other. Start at the lowest possible dose. |
| Other Alpha-Blockers | Tamsulosin, Doxazosin, Prazosin | Additive hypotensive effects, potentially severe. | Avoid combination due to increased risk without significant added benefit. |
| Calcium Channel Blockers | Verapamil | Augmented blood pressure lowering, high risk of hypotension and fainting. | Monitor closely and adjust dosages. Caution is advised. |
| Alcohol (Ethanol) | Beer, Wine, Spirits | Increased risk of hypotension, especially initially. | Avoid or limit intake significantly, particularly with initial doses. |
| Yohimbe | Herbal Supplement | Potentiates hypotensive effects, causing severe hypotension. | Contraindicated. Avoid this supplement entirely when taking terazosin. |
Managing Potential Side Effects
- Sit or lie down at the first sign of dizziness, lightheadedness, or feeling faint.
- Move slowly when changing positions, such as going from lying down to sitting or standing.
- Stay hydrated and avoid overheating, as this can worsen low blood pressure.
- Report all side effects to your healthcare provider, particularly if they are severe or do not improve.
- Keep all healthcare appointments for blood pressure checks and medication monitoring.
Conclusion
While terazosin is an important medication for managing hypertension and BPH, its efficacy relies on careful management of potential drug interactions. Taking terazosin with other alpha-blockers, PDE-5 inhibitors, verapamil, or alcohol can lead to a dangerous and sudden drop in blood pressure. To ensure safety, always provide your healthcare provider with a complete list of all medications, including over-the-counter products, supplements, and herbal remedies. Never start, stop, or change the dosage of any medication without first consulting a professional. This proactive approach is the best way to prevent adverse interactions and ensure the best treatment outcomes.
For more information on terazosin, including uses and side effects, visit the MedlinePlus Drug Information page.
