Formulary
Doxazosin: Indications, Dosing, Side Effects and Interactions
Doxazosin clinical drug profile including indications, dosing, side effects, cautions and interactions.
MedNext Academy | 4 min read
Doxazosin: Indications, Dosing, Side Effects and Interactions
Doxazosin clinical drug profile including indications, dosing, side effects, cautions and interactions.
Indications and dose
**Hypertension**
- **Adult** (By Mouth Using Immediate-Release Medicines): Initially 1 mg once daily for 1-2 weeks, then increased to 2 mg once daily, then increased if necessary to 4 mg once daily, usual dose up to 4 mg once daily; increased if necessary up to 16 mg once daily.
- **Adult** (By Mouth Using Modified-Release Medicines): Initially 4 mg once daily, then increased if necessary to 8 mg once daily, dose can be adjusted after 4 weeks.
**Benign prostatic hyperplasia**
- **Adult** (By Mouth Using Immediate-Release Medicines): Initially 1 mg once daily, usual maintenance 2-4 mg once daily, dose may be doubled at intervals of 1-2 weeks according to response; increased if necessary up to 8 mg once daily.
- **Adult** (By Mouth Using Modified-Release Medicines): Initially 4 mg once daily, then increased if necessary to 8 mg once daily, dose can be adjusted after 4 weeks.
**Hypertension for doxazosin**
- **Child 6-11 years** (By mouth using immediate-release medicines): Initially 0.5 mg once daily, then increased to 2-4 mg once daily, dose should be increased at intervals of 1 week.
- **Child 12-17 years** (By mouth using immediate-release medicines): Initially 1 mg once daily for 1-2 weeks, then increased to 2 mg once daily, then increased if necessary to 4 mg once daily, rarely doses of up to 16 mg per day may be required.
**Dysfunctional voiding (initiated under specialist supervision) for doxazosin**
- **Child 4-11 years** (By mouth using immediate-release medicines): Initially 0.5 mg daily, adjusted according to response, dose should be increased at monthly intervals; maximum 2 mg per day.
- **Child 12-17 years** (By mouth using immediate-release medicines): Initially 1 mg daily, adjusted according to response, dose may be doubled at intervals of 1 month; usual maintenance 2-4 mg daily; maximum 8 mg per day.
Cautions
Care with initial dose (postural hypotension); cataract surgery (risk of intra-operative floppy iris syndrome); elderly; heart failure; pulmonary oedema due to aortic or mitral stenosis
Contraindications
History of micturition syncope (in patients with benign prostatic hypertrophy); history of postural hypotension; monotherapy in patients with overflow bladder or anuria
Side effects
Common or very common Arrhythmias; asthenia; chest pain; cough; cystitis; dizziness; drowsiness; dry mouth; dyspnoea; gastrointestinal discomfort; headache; hypotension; increased risk of infection; influenza like illness; muscle complaints; nausea; oedema; pain; palpitations; skin reactions; urinary disorders; vertigo Uncommon Angina pectoris; anxiety; appetite abnormal; arthralgia; constipation; depression; diarrhoea; gastrointestinal disorders; gout; haemorrhage; insomnia; myocardial infarction; sensation abnormal; sexual dysfunction; stroke; syncope; tinnitus; tremor; vomiting; weight increased Rare or very rare Alopecia; bronchospasm; flushing; gynaecomastia; hepatic disorders; leucopenia; malaise; muscle weakness; thrombocytopenia; vision blurred Frequency not known Floppy iris syndrome
Interactions
**Severe interactions:**
- Anti-hypertensives (including calcium channel blockers) The co-administration of doxazosin (4 and 8 mg daily) and tadalafil (5 mg daily dose and 20 mg as a single dose) increases the blood...
**Other interactions (8):**
- In three specific drug-drug interaction studies, the alpha-blocker doxazosin (4 mg and 8 mg) and sildenafil (25 mg, 50 mg, or 100 mg) were administered simultaneously to patients with benign...
- When sildenafil and doxazosin were administered simultaneously to patients stabilized on doxazosin therapy, there were infrequent reports of patients who experienced symptomatic postural hypotension.
- The hypotensive effect of vasodilator antihypertensive agents such as hydralazine and -blockers (e.g.
- The hypotensive effect of vasodilator antihypertensive agents such as hydralazine and blockers (e.g.
- Alpha-blockers Haemodynamic interactions with doxazosin and tamsulosin were studied in healthy subjects in a two-period crossover-design trial.
- In patients receiving stable doxazosin treatment, the placebo-subtracted mean maximum decreases in standing and supine systolic blood pressure following avanafil dosing were 2.5 mmHg and 6.0 mmHg,...
Pregnancy
No evidence of teratogenicity; manufacturers advise use only when potential benefit outweighs risk.
Breast feeding
Accumulates in milk in animal studies-manufacturer advises avoid.
Hepatic impairment
Manufacturer advises caution in mild to moderate impairment (limited information available); avoid in severe impairment (no information available).
Medicinal forms
Capsule,Tablet,Tablet
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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