From the Guidelines
The maximum dose of doxazosin is 16 mg once daily. Typically, treatment begins with a lower dose of 1 mg once daily, which is then gradually increased based on the patient's response and tolerance. Dose adjustments are usually made at 1-2 week intervals, progressing through 2 mg, 4 mg, 8 mg, and potentially up to the maximum of 16 mg daily. This gradual titration helps minimize side effects, particularly orthostatic hypotension (a sudden drop in blood pressure when standing up), which is most common when starting therapy or increasing doses. Doxazosin is an alpha-1 adrenergic blocker primarily used to treat hypertension and benign prostatic hyperplasia (BPH). It works by relaxing blood vessels and smooth muscle in the prostate and bladder neck. Patients should take doxazosin at the same time each day, and the first dose should be taken at bedtime to reduce the risk of dizziness or fainting. If a dose is missed, patients should take it as soon as remembered, but should never double the dose. According to the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1, the usual dose range for doxazosin is 1-16 mg once daily.
Some key points to consider when prescribing doxazosin include:
- Starting with a low dose and gradually increasing as needed and tolerated
- Monitoring for orthostatic hypotension, especially in older adults
- Avoiding abrupt cessation of therapy to prevent rebound hypertension
- Considering alternative agents or combination therapy for patients with concomitant hypertension and cardiac risk factors, as doxazosin monotherapy may be associated with a higher incidence of congestive heart failure 1.
Overall, doxazosin is a effective treatment option for hypertension and BPH, but requires careful dosing and monitoring to minimize side effects and optimize therapeutic outcomes.
From the FDA Drug Label
2.2 Benign Prostatic Hyperplasia ... The maximum recommended dose for BPH is 8 mg once daily. 2.3 Hypertension ... Daily dosage may be doubled up 16 mg once daily, as needed, to achieve the desired reduction in blood pressure. The maximal dose of Doxazosin is 16 mg once daily for hypertension and 8 mg once daily for Benign Prostatic Hyperplasia, as the dose can be doubled up to 16 mg for hypertension but has a maximum recommended dose of 8 mg for BPH 2.
From the Research
Maximal Dose of Doxazosin
The maximal dose of Doxazosin (alpha-1 adrenergic blocker) can be determined from several studies:
- In the study 3, Doxazosin was administered at doses of 4 mg, 8 mg, and 12 mg.
- The study 4 mentions that the starting dose of Doxazosin was 1 mg with upward titrations at 2-week intervals to a stable, efficacious, and well-tolerated dose, with mean daily doses of 4 mg and 6.4 mg for normotensive and hypertensive men, respectively.
- The study 5 reports that 88% of patients underwent dose titration to a maximum of 8 mg Doxazosin once daily.
- The study 6 states that Doxazosin was initiated at a dosage of 0.5 or 1 mg once daily, with a final dose range of up to 12 mg once daily.
- The study 7 compared the efficacy and tolerability of Doxazosin in the gastrointestinal therapeutic system (GITS) formulation, Doxazosin standard, and placebo, with Doxazosin GITS initiated at 4 mg once daily and titrated to 8 mg once daily after 7 weeks, if indicated.
Key Findings
Some key findings related to the maximal dose of Doxazosin include:
- The maximum dose of Doxazosin mentioned in the studies is 12 mg once daily 3, 6.
- The mean daily doses of Doxazosin were 4 mg and 6.4 mg for normotensive and hypertensive men, respectively 4.
- Nearly half of the patients on Doxazosin GITS achieved symptom relief at the 4-mg starting dose 7.
- A similar number of patients in both Doxazosin groups were titrated to the maximum dose of 8 mg for both formulations 7.