From the Guidelines
Doxazosin at a dose of 8 mg is associated with common side effects including dizziness, lightheadedness, fatigue, headache, and postural hypotension, as well as more serious but less common side effects such as fainting, priapism, and allergic reactions, as noted in the 2018 guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1. The primary adverse events reported with alpha-blocker therapy, such as doxazosin, are orthostatic hypotension, dizziness, tiredness, ejaculatory problems, and nasal congestion, according to the 2003 AUA guideline on management of benign prostatic hyperplasia 1. Some key points to consider when prescribing doxazosin include:
- Starting with a lower dose, such as 1 mg, and gradually increasing as needed and tolerated
- Taking the medication at bedtime to minimize dizziness
- Being aware of the first-dose phenomenon, where blood pressure drops significantly after the initial dose
- Monitoring for signs of orthostatic hypotension, such as dizziness or lightheadedness when standing up
- Considering the potential for ejaculatory problems and other sexual side effects
- Avoiding use in patients with certain medical conditions, such as severe bilateral renal artery stenosis or significant renal dysfunction. It's also important to note that doxazosin may be used in combination with other medications to treat high blood pressure and symptoms of BPH, and that patients should be closely monitored for potential interactions and side effects, as recommended in the 2018 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.
From the FDA Drug Label
The MTOPS Study was not specifically designed to make statistical comparisons between groups for reported adverse experiences. The incidence rates of drug-related adverse experiences reported by ≥2% of patients in any treatment group in the MTOPS Study are listed in Table 2 The individual adverse effects which occurred more frequently in the combination group compared to either drug alone were: asthenia, postural hypotension, peripheral edema, dizziness, decreased libido, rhinitis, abnormal ejaculation, impotence and abnormal sexual function Table 2: Incidence ≥2% in One or More Treatment Groups Drug-Related Clinical Adverse Experiences in MTOPS Doxazosin 4 mg or 8 mg* (N=756) (%) Asthenia 15.7 Headache 4.1 Hypotension 3.4 Postural Hypotension 16.7 Peripheral Edema 2.6 Dizziness 17.7 Libido Decreased 7.0 Somnolence 3.7 Dyspnea 2.1 Rhinitis 1.3 Abnormal Ejaculation 4.5 Gynecomastia 1.1 Impotence 14.4 Sexual Function Abnormal 2.0
The side effects of 8 milligrams of doxazosin (Cardura) include:
- Asthenia (15.7%)
- Postural Hypotension (16.7%)
- Dizziness (17.7%)
- Decreased Libido (7.0%)
- Abnormal Ejaculation (4.5%)
- Impotence (14.4%)
- Abnormal Sexual Function (2.0%) 2
From the Research
Side Effects of 8 Milligrams of Doxazosin (Cardura)
- The most commonly reported adverse effects of alpha(1)-adrenoceptor antagonists, such as doxazosin, are dizziness, asthenia, postural hypotension, and syncope 3
- Doxazosin has been shown to be effective in relieving lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH), but may cause adverse effects such as asthenia, dizziness, and postural hypotension 4
- Compared to finasteride, doxazosin has a higher risk of asthenia, dizziness, and postural hypotension, but finasteride has a higher risk of impotence, erectile dysfunction, decreased libido, and ejaculation disorder 4
- The pharmacokinetics of extended-release forms of doxazosin is food-sensitive, and it may interact with grapefruit juice and citrus fruits, leading to intensified adverse effects 5
- Alpha-1 adrenergic receptor antagonists, such as doxazosin, may interact with alcohol, leading to orthostatic hypotension 5
Specific Adverse Effects
- Dizziness: a common adverse effect of doxazosin 3, 4
- Asthenia: a common adverse effect of doxazosin 3, 4
- Postural hypotension: a common adverse effect of doxazosin 3, 4
- Syncope: a possible adverse effect of doxazosin 3
- Impotence: a possible adverse effect of finasteride, but not doxazosin 4
- Erectile dysfunction: a possible adverse effect of finasteride, but not doxazosin 4
- Decreased libido: a possible adverse effect of finasteride, but not doxazosin 4
- Ejaculation disorder: a possible adverse effect of finasteride, but not doxazosin 4