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Medication Safety Issues
Sound-alike/look-alike issues:
Flomax® may be confused with Flonase®, Flovent®, Foltx®, Fosamax®, Volmax®
Tamsulosin may be confused with tacrolimus, tamoxifen, terazosin
International issues:
Flomax®: Brand name for morniflumate in Italy
Flomax® may be confused with Flomox® which is a brand name for cefcapene in Japan
Pronunciation
(tam SOO loe sin)
U.S. Brand Names
Index Terms
Generic Available
No
Canadian Brand Names
Pharmacologic Category
Pharmacologic Category Synonyms
Use: Labeled Indications
Treatment of signs and symptoms of benign prostatic hyperplasia (BPH)
Use: Unlabeled/Investigational
Symptomatic treatment of bladder outlet obstruction or dysfunction
Pregnancy Risk Factor
B
Pregnancy Considerations
Teratogenic effects were not observed in animal studies, however, tamsulosin is not approved for use in women.
Contraindications
Hypersensitivity to tamsulosin or any component of the formulation
Warnings/Precautions
Concerns related to adverse effects:
• Angina: Discontinue if symptoms of angina occur or worsen.
• Floppy iris syndrome: Intraoperative floppy iris syndrome has been observed in cataract surgery patients who were on or were previously treated with alpha1-blockers; causality has not been established and there appears to be no benefit in discontinuing alpha-blocker therapy prior to surgery.
• Orthostatic hypotension/syncope: May cause significant orthostatic hypotension and syncope, especially with first dose; anticipate a similar effect if therapy is interrupted for a few days, if dosage is rapidly increased, or if another antihypertensive drug (particularly vasodilators) or a PDE-5 inhibitor (eg, sildenafil, tadalafil, vardenafil) is introduced. “First-dose” orthostatic hypotension may occur 4-8 hours after dosing; may be dose related. Patients should be cautioned about performing hazardous tasks when starting new therapy or adjusting dosage upward.
• Priapism: Priapism has been associated with use (rarely).
• Sulfonamide allergy: Rarely, patients with a sulfa allergy have also developed an allergic reaction to tamsulosin; avoid use when previous reaction has been severe.
Disease-related concerns:
• Prostate cancer: It is recommended to rule out prostatic carcinoma before beginning therapy.
Special populations:
• Females: Not indicated for use in women.
• Pediatrics: Not indicated for use in children.
Other warnings/precautions:
• Antihypertensive use: Not intended for use as an antihypertensive drug.
Adverse Reactions
>10%:
Cardiovascular: Orthostatic hypotension (6 % to 19%)
Central nervous system: Headache (19% to 21%), dizziness (15% to 17%)
Genitourinary: Abnormal ejaculation (8% to 18%)
Respiratory: Rhinitis (13% to 18%)
Miscellaneous: Infection (9% to 11%)
1% to 10%:
Cardiovascular: Chest pain (4%)
Central nervous system: Somnolence (3% to 4%), insomnia (1% to 2%), vertigo (?1%)
Endocrine & metabolic: Libido decreased (1% to 2%)
Gastrointestinal: Diarrhea (4% to 6%), nausea (3% to 4%), tooth disorder (1% to 2%)
Neuromuscular & skeletal: Weakness (8% to 9%), back pain (7% to 8%)
Ocular: Blurred vision (?2%)
Respiratory: Pharyngitis (5% to 6%), cough (3% to 5%), sinusitis (2% to 4%)
<1%, postmarketing, and/or case reports (limited to important or life-threatening): Allergic reactions (angioedema, pruritus, rash, urticaria, respiratory symptoms); constipation, hypotension, intraoperative floppy iris syndrome, orthostasis (symptomatic), palpitation, priapism, skin desquamation, syncope, vomiting
Metabolism/Transport Effects
Substrate (major) of CYP2D6, 3A4
Drug Interactions
Alfuzosin: Alpha1-Blockers may enhance the antihypertensive effect of Alfuzosin. Risk of orthostatic hypotension or syncope may be increased. Alfuzosin may enhance the antihypertensive effect of Alpha1-Blockers. Risk X: Avoid combination
Alpha1-Blockers: May enhance the antihypertensive effect of Tamsulosin. Risk of orthostatic hypotension or syncope may be increased. Tamsulosin may enhance the antihypertensive effect of Alpha1-Blockers. Risk X: Avoid combination
Beta-Blockers: May enhance the orthostatic effect of Alpha1-Blockers. The risk associated with ophthalmic products is probably less than systemic products. Exceptions: Levobunolol; Metipranolol. Risk D: Consider therapy modification
Calcium Channel Blockers: Alpha1-Blockers may enhance the hypotensive effect of Calcium Channel Blockers. Risk C: Monitor therapy
CYP2D6 Inhibitors (Moderate): May decrease the metabolism of CYP2D6 Substrates. Risk C: Monitor therapy
CYP2D6 Inhibitors (Strong): May decrease the metabolism of CYP2D6 Substrates. Risk D: Consider therapy modification
CYP3A4 Inducers (Strong): May increase the metabolism of CYP3A4 Substrates. Risk C: Monitor therapy
CYP3A4 Inhibitors (Moderate): May decrease the metabolism of CYP3A4 Substrates. Risk C: Monitor therapy
CYP3A4 Inhibitors (Strong): May decrease the metabolism of CYP3A4 Substrates. Risk D: Consider therapy modification
Darunavir: May increase the serum concentration of CYP2D6 Substrates. Risk C: Monitor therapy
Dasatinib: May increase the serum concentration of CYP3A4 Substrates. Risk C: Monitor therapy
Deferasirox: May decrease the serum concentration of CYP3A4 Substrates. Risk C: Monitor therapy
Herbs (CYP3A4 Inducers): May increase the metabolism of CYP3A4 Substrates. Risk C: Monitor therapy
MAO Inhibitors: May enhance the orthostatic effect of Orthostasis Producing Agents. Risk C: Monitor therapy
Peginterferon Alfa-2b: May decrease the serum concentration of CYP2D6 Substrates. Risk C: Monitor therapy
Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Alpha1-Blockers. Management: Ensure patient is stable on alpha 1 blocker before starting PDE5 inhibitor; initiate PDE5 inhibitor at lowest possible dose. If patient stable on PDE5 inhibitor, initiate alpha 1 blocker at lowest dose. Risk D: Consider therapy modification
Silodosin: Alpha1-Blockers may enhance the adverse/toxic effect of Silodosin. Of particular concern are the risk of postural hypotension, syncope, and/or hypotension. Silodosin may enhance the hypotensive effect of Alpha1-Blockers. Of particular concern are the risk of postural hypotension, syncope, and/or hypotension. Risk X: Avoid combination
Ethanol/Nutrition/Herb Interactions
Food: Fasting increases bioavailability by 30% and peak concentration 40% to 70%.
Herb/Nutraceutical: St John's wort: May decrease the levels/effects of tamsulosin. Avoid herbs with hypotensive properties (black cohosh, California poppy, coleus, golden seal, hawthorn, mistletoe, periwinkle, quinine, Shepherd's purse); may enhance the hypotensive effect of tamsulosin. Avoid saw palmetto (due to limited experience with this combination).
Storage
Store at room temperature of 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).
Mechanism of Action
Tamsulosin is an antagonist of alpha1A-adrenoreceptors in the prostate. Smooth muscle tone in the prostate is mediated by alpha1A-adrenoreceptors; blocking them leads to relaxation of smooth muscle in the bladder neck and prostate causing an improvement of urine flow and decreased symptoms of BPH. Approximately 75% of the alpha1-receptors in the prostate are of the alpha1A subtype.
Pharmacodynamics/Kinetics
Absorption: >90%
Protein binding: 94% to 99%, primarily to alpha1 acid glycoprotein (AAG)
Metabolism: Hepatic via CYP3A4 and 2D6; metabolites undergo extensive conjugation to glucuronide or sulfate
Bioavailability: Fasting: 30% increase
Distribution: Vd: 16 L
Steady-state: By the fifth day of once-daily dosing
Half-life elimination: Healthy volunteers: 9-13 hours; Target population: 14-15 hours
Time to peak: Fasting: 4-5 hours; With food: 6-7 hours
Excretion: Urine (76%, <10% as unchanged drug); feces (21%)
Dosage
Oral: Adults:
BPH: 0.4 mg once daily ~30 minutes after the same meal each day; dose may be increased after 2-4 weeks to 0.8 mg once daily in patients who fail to respond. If therapy is interrupted for several days, restart with 0.4 mg once daily.
Bladder outlet obstruction (unlabeled use): 0.4 mg once daily ~30 minutes after the same meal each day
Dosage adjustment in renal impairment:
Clcr ?10 mL/minute: No adjustment needed
Clcr <10 mL/minute: Not studied
Dosage adjustment in hepatic impairment:
Mild-to-moderate impairment: No adjustment needed
Severe impairment: Not studied
Administration: Oral
Administer 30 minutes after the same meal each day. Capsules should be swallowed whole; do not crush, chew, or open.
Dietary Considerations
Take once daily, 30 minutes after the same meal each day.
Patient Education
Do not take any new medication during therapy without consulting prescriber. Take as directed; do not skip dose or discontinue without consulting prescriber. May cause drowsiness, dizziness, or impaired judgment with first doses (use caution when driving or engaging in tasks that require alertness until response to drug is known); postural hypotension (use caution when rising from sitting or lying position or when climbing stairs); nausea (frequent mouth care or sucking lozenges may help); urinary incontinence (void before taking medication); ejaculatory disturbance (reversible, may resolve with continued use of drug); diarrhea; palpitations or rapid heartbeat; respiratory difficulty, unusual cough, or sore throat; or other persistent side effects. Report palpitations or rapid heartbeat; respiratory difficulty; muscle weakness, fatigue, or pain; vision changes or hearing; rash; changes in urinary pattern; or other persistent side effects.
Geriatric Considerations
Metabolism of tamsulosin may be slower, and older patients may be more sensitive to the orthostatic hypotension caused by this medication. A 40% higher exposure (AUC) is anticipated in patients between 55 and 75 years of age as compared to younger subjects (20-32 years).
Anesthesia and Critical Care Concerns/Other Considerations
Clinical Pearls/Comments: Tamsulosin may induce significant orthostatic hypotension with lightheadedness and possible loss of consciousness.
Cardiovascular Considerations
Tamsulosin should not be used as an antihypertensive agent despite its alpha-blocking properties. It may induce significant orthostatic hypotension with lightheadedness and possible loss of consciousness.
Dental Health: Effects on Dental Treatment
Key adverse event(s) related to dental treatment: Orthostatic hypotension and tooth disorder.
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
Dizziness is common; may cause drowsiness or insomnia
Mental Health: Effects on Psychiatric Treatment
None reported
Nursing: Physical Assessment/Monitoring
Not for use as an antihypertensive. Assess potential for interactions with other pharmacological agents patient may be taking (eg, increased risk of hypotension). Assess results of periodic lipid panels, therapeutic effectiveness (improved urine flow), and adverse reactions (eg, “first dose” orthostatic hypotension, headache, gastrointestinal disturbance [nausea, vomiting], cough) at beginning of therapy and on a regular basis with long-term therapy. When discontinuing, dose should be tapered and blood pressure monitored closely. Teach patient proper use, possible side effects/appropriate interventions, and adverse symptoms to report.
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule, as hydrochloride:
Flomax®: 0.4 mg
Pricing: U.S. (www.drugstore.com)
Capsule, 24-hour (Flomax)
0.4 mg (30): $119.67
References
Chang DF and Campbell JR, “Intraoperative Floppy Iris Syndrome Associated With Tamsulosin,” J Cataract Refract Surg, 2005, 31(4):664-73.
Goldman HB and Zimmern PE, “The Treatment of Female Bladder Outlet Obstruction,” BJU Int, 2006, 98(Suppl 1):17-23.
Pischedda A, Pirozzi Farina F, Madonia M, et al, “Use of Alpha1-Blockers in Female Functional Bladder Neck Obstruction,” Urol Int, 2005, 74(3):256-61.
Rossi C, Kortmann BB, Sonke GS, et al, “Alpha-Blockade Improves Symptoms Suggestive of Bladder Outlet Obstruction But Fails to Relieve It,” J Urol, 2001, 165(1):38-41.
International Brand Names
Lexi-Comp.com
Last full review/revision August 2009
Content last modified August 2009
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