What is the maximum recommended dose of Prazosin (prazosin) XL?

Maximum Dose of Prazosin XL

The maximum recommended dose of prazosin extended-release (XL) formulations is 20 mg once daily. 1, 2

Standard Dosing Parameters

For extended-release prazosin (Minipress XL/Prazosin GITS):

• Maximum dose: 20 mg once daily 2
• Typical effective range: 10-20 mg once daily 2
• This formulation uses gastro-intestinal therapeutic system (GITS) technology for sustained 24-hour release 2

For immediate-release prazosin (standard formulation):

• Maximum dose: 20 mg per day in 2-3 divided doses 3, 1
• Typical dosing: 2-20 mg/day divided 2-3 times daily 3, 4

Context-Specific Maximum Doses

Hypertension

• Extended-release: Up to 20 mg once daily 2
• Immediate-release: Up to 20 mg/day in divided doses 1
• The FDA label explicitly states 20 mg per day as the usual maximum recommended human dose 1

PTSD-Related Nightmares

• Doses have been studied up to 20 mg/day in clinical trials 5
• Mean effective doses typically range from 3.1 mg to 15.6 mg 3
• One large VA study used a maximum of 20 mg with mean dose of 14.8 ± 6.1 mg 5
• Some protocols use bedtime dosing plus mid-morning dosing 3

Critical Safety Considerations

First-dose hypotension is a major concern:

• The initial dose should always be 1 mg at bedtime to minimize syncope risk 1
• In clinical experience with 22,000 patients, syncope occurred in 0.15% (1 in 667) when starting with 1 mg 6
• Crushing or breaking extended-release tablets causes rapid absorption with severe hypotension risk 4

Orthostatic hypotension monitoring:

• Elderly patients are particularly susceptible and require careful blood pressure monitoring 3, 7
• Check for dizziness and lightheadedness when standing 7, 1
• Avoid combining with PDE-5 inhibitors without dose adjustment due to additive hypotensive effects 1

Common Pitfalls to Avoid

• Never crush or break extended-release formulations - this destroys sustained-release properties and risks severe hypotension 4
• Do not start at high doses - always begin with 1 mg at bedtime regardless of formulation 1, 6
• Do not exceed 20 mg/day total - this is the FDA-established maximum for safety 1
• Do not assume XL and immediate-release are interchangeable - XL is once daily; immediate-release requires 2-3 times daily dosing 3, 2

Dose Titration Strategy

For extended-release prazosin:

• Start: 2.5 mg once daily 2
• Titrate to: 10 mg or 20 mg once daily based on response 2
• Monitor blood pressure at each dose adjustment 7

For immediate-release prazosin:

• Start: 1 mg at bedtime 1
• Titrate: Increase gradually to 1-2 mg 2-3 times daily 3
• Maximum: 20 mg/day in divided doses 1