tamsulosin, Flomax

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Pharmacy Author:

Omudhome Ogbru, PharmD

Omudhome Ogbru, PharmD

Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

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Medical and Pharmacy Editor:

Jay W. Marks, MD

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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GENERIC NAME: tamsulosin

BRAND NAME: Flomax

DRUG CLASS AND MECHANISM: Tamsulosin is an oral drug for the treatment of men who are having difficulty urinating because of benign prostatic hyperplasia (BPH). In men, the tube which carries urine from the bladder to the penis (called the urethra) travels 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 which 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. Tamsulosin was approved by the FDA in 1997.

GENERIC AVAILABLE: Yes

PRESCRIPTION: Yes

PREPARATIONS: Capsules: 0.4mg.

STORAGE: Capsules should be stored at room temperature, 15-30 C (59-86 F).

PRESCRIBED FOR: Tamsulosin is used to treat men who are having problems urinating because of BPH. Tamsulosin is not approved for the treatment of high blood pressure.

DOSING: The recommended dose is 0.4 or 0.8 mg 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.

DRUG INTERACTIONS: The elimination of tamsulosin from the body may be reduced by erythromycin, 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 tamsulosin. PDE-5 inhibitors (for example, vardenafil [Levitra, Staxyn], Adcirca, sildenafil [Viagra, Revatio], tadalafil [Cialis]) add to the blood pressure lowering effects of tamsulosin and may result in severe blood pressure reduction.

PREGNANCY: Tamsulosin is not prescribed for women.

NURSING MOTHERS: This medication is used only in men. It is not known if tamsulosin is secreted into breast milk.

SIDE EFFECTS: The most common adverse effects of tamsulosin are anemia (decreased red blood cells), decreased white blood cells, nausea, vomiting, abnormal taste, increased triglycerides, and weakness. Low blood pressure, dizziness or fainting, headache, abdominal pain, weight loss, muscle pain, abnormal ejaculation, upper respiratory tract infections, and rash also may occur. Orthostatic hypotension (low blood pressure when rising from sitting or lying down position), priapism (prolonged erection), and an eye problem called intraoperative floppy iris syndrome (IFIS) have been observed during tamsulosin treatment.

Reference: FDA Prescribing Information

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