What is the dosage for Flomax (tamsulosin)?
- The recommended starting dose is 0.4 once daily about 30 minutes after the same meal time each day.
- When taken on an empty stomach, more of the medication is absorbed.
- This could cause a greater effect and potentially a drop in blood pressure.
- The dose may be increased to 0.8 mg once daily after 2 to 4 weeks if the response is not adequate.
- The capsules should not be crushed, chewed or opened.
Which drugs or supplements interact with Flomax (tamsulosin)?
The elimination of Flomax from the body may be reduced by:
- ketoconazole (Nizoral, Extina, Xolegel, Kuric),
- paroxetine (Paxil),
- cimetidine (Tagamet),
- ritonavir (Norvir),
- lopinavir, and
- other drugs that reduce the elimination of drugs by liver enzymes.
Reduced elimination may lead to increased side effects of Flomax. PDE-5 inhibitors (for example, vardenafil [Levitra, Staxyn], Adcirca, sildenafil [Viagra, Revatio], tadalafil [Cialis]) add to the blood pressure lowering effects of Flomax and may result in severe blood pressure reduction.
Is Flomax (tamsulosin) safe to use during pregnancy or while breastfeeding?
- Flomax is not prescribed for women.
- This medication is used only in men. It is not known if Flomax is secreted into human milk.
What else should I know about Flomax (tamsulosin)?
What preparations of Flomax (tamsulosin) are available?
Capsules: 0.4 mg.
How should I keep Flomax (tamsulosin) stored?
Capsules should be stored at room temperature, 15 C to 30 C (59 F to 86 F).
How does Flomax (tamsulosin) work?
- In men, the tube which carries urine from the bladder through the penis (called the urethra) passes through the prostate gland. As men get older, the prostate gland enlarges, and the muscle cells within the prostate gland and the neck of the bladder (which controls the flow of urine) tighten. The combination of enlargement and tightening of muscles compresses the urethra and obstructs the flow of urine. This results in difficulty urinating and retention of urine within the bladder. The tightening or contraction of the muscle cells is controlled by nerves. One type of nerve, the alpha adrenergic nerves, cause the muscle cells to tighten by releasing a chemical related to epinephrine (adrenalin). Tamsulosin blocks the effects of this chemical on the muscle cells and causes the muscles to relax. This results in a decrease in obstruction to the flow of urine.
- There are other drugs that block alpha adrenergic nerves throughout the body and which are used in treating diseases of the heart, blood vessels, and prostate for example, prazosin (Minipress), terazosin (Hytrin), doxazosin (Cardura), and alfuzosin (Uroxatral). Tamsulosin is more active against the alpha adrenergic nerves of the prostate and bladder neck than these other drugs and has a lesser effect on alpha adrenergic nerves elsewhere in the body. For this reason, tamsulosin causes fewer side effects, especially low blood pressure, than other alpha adrenergic blocking drugs. Moreover, tamsulosin therapy can be started at the optimum dose whereas other alpha adrenergic blocking drugs need to be started at low doses with the doses slowly increased over time in order to minimize the side effects.
When was Flomax (tamsulosin) approved by the FDA?
Tamsulosin was approved by the FDA in 1997.
Medically reviewed by Eni Williams, PharmD, PhD
Reference: FDA Prescribing Information
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