From the Guidelines
The dose of Flomax (tamsulosin) can be increased from 0.4mg to 0.8mg if needed, but this should be done under the guidance of a doctor and with careful monitoring of side effects. According to the American Urological Association (AUA) guideline on management of benign prostatic hyperplasia 1, the use of alpha-blocker therapy, including tamsulosin, is based on the hypothesis that clinical BPH is partly caused by alpha1-adrenergic-mediated contraction of prostatic smooth muscle, resulting in bladder outlet obstruction. The guideline notes that maximum tolerable and effective doses have not been defined for any alpha blocker, but reported clinical data support the efficacy and safety of titrating patients to 8 mg of doxazosin, to 0.8 mg of tamsulosin (from 0.4 mg), and to 10 mg of terazosin 1. Some key points to consider when increasing the dose of Flomax include:
- The primary adverse events reported with alpha-blocker therapy are orthostatic hypotension, dizziness, tiredness (asthenia), ejaculatory problems, and nasal congestion 1
- Tamsulosin appears to have a lower probability of orthostatic hypotension but a higher probability of ejaculatory dysfunction than the other alpha blockers 1
- If symptoms are not improving on 0.4 mg of Flomax after several weeks, consulting a doctor may be necessary to consider switching medications or adding another treatment rather than doubling the Flomax dose. It is essential to weigh the potential benefits of increasing the dose against the potential risks and to closely monitor patients for any adverse effects.
From the FDA Drug Label
Tamsulosin Hydrochloride Capsules 0.4 mg once daily is recommended as the dose for the treatment of the signs and symptoms of BPH. ... For those patients who fail to respond to the 0. 4 mg dose after 2 to 4 weeks of dosing, the dose of Tamsulosin Hydrochloride Capsules can be increased to 0.8 mg once daily. ... If Tamsulosin Hydrochloride Capsules administration is discontinued or interrupted for several days at either the 0.4 mg or 0.8 mg dose, therapy should be started again with the 0.4 mg once-daily dose.
The dose of Flomax (tamsulosin) can be increased from 0.4mg to 0.8mg, but this should be done after 2 to 4 weeks of dosing with the 0.4mg dose if the patient fails to respond, not in several days 2.
From the Research
Dose Increase of Flomax (Tamsulosin)
- The dose of Flomax (tamsulosin) can be increased from 0.4mg to 0.8mg if needed, as shown in a pilot study where three-fourths of patients who progressed after initial response to 0.4mg achieved a durable response with the 0.8mg dose 3.
- However, increasing the dose of tamsulosin from 0.4 to 0.8mg seemed to have no substantial additional benefit in a long-term study, where the incidence of treatment responders remained stable throughout the 4-year period 4.
- Adverse effects increased markedly as tamsulosin dosing increased, and were reported in 75% of men receiving the 0.8mg dose, with the most frequently reported adverse events including dizziness, rhinitis, and abnormal ejaculation 5.
- The beneficial effects of tamsulosin on voiding symptoms, peak urinary flow rate, and bladder emptying appear to be dose-related, up to a ceiling dose of 0.4mg, and the usual dosage of tamsulosin was 0.4 or 0.8mg orally once a day in various studies 6, 7.
- Dosage titration at the start of treatment is not necessary, and tamsulosin has a rapid onset of action and is effective in patients with moderate or severe symptoms 6, 7.