Terazosin tablets will no longer be available in New Zealand once current supplies are exhausted. PHARMAC notification is available here. 

Terazosin is an alpha-blocker approved to treat benign prostatic hyperplasia (BPH) and/or hypertension. 

For BPH, doxazosin is a suitable alternative: 

• Doxazosin is an alpha-blocker with similar adverse effects and potential for drug interactions as terazosin. See NZF. 
• A direct switch is reasonable. Start at approximately 50% of the terazosin dose (adjusted to tablet size) and titrate. E.g. If the patient is taking terazosin 5 mg at night switch to doxazosin 2 mg at night and adjust the dose from there. 
• Adjust the dose according to urinary symptoms and adverse effects (e.g. postural hypotension). Consider closer monitoring and slower dose titration for patients who will be most impacted by the consequences of falls (e.g. frail, older adults). 
• Advise patients to take doxazosin at bedtime during dose titration and to take care when moving from sitting or lying, to standing. They may feel lightheaded or dizzy and performance of skilled tasks such as driving may be affected.  
• There are no comparative trials of doxazosin and terazosin for BPH. ‘Real world’ switching studies in men aged 40 to 87 years with BPH found terazosin 5 mg at night had similar efficacy and adverse effects as doxazosin 4 mg at night in most patients. 

For hypertension, consider if an alpha–blocker is still needed to achieve blood pressure targets: 

• Alpha-blockers are fourth-line agents for hypertension, only added when blood pressure targets are not achieved with 3 other antihypertensives. See ‘Hypertension’ in Community HealthPathways. Alternatively, BPAC has published articles on blood pressure targets and managing blood pressure in primary care. 
• If an alpha-blocker is still indicated, follow the switching advice above for BPH. Comparative trials of terazosin and doxazosin for hypertension show greater individual variation in dose equivalency (doxazosin doses being 40 to 80% of terazosin doses). 

Health professionals are welcome to contact our service for more specific advice on individual patients.