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Flomax

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Flomax

Side Effects
Interactions

SIDE EFFECTS

Clinical Trials Experience

Because clinical studies are conducted under widely varying conditions, adverse reactions rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in practice.

The incidence of treatment-emergent adverse events has been ascertained from six short-term U.S. and European placebo-controlled clinical trials in which daily doses of 0.1 to 0.8 mg FLOMAX capsules were used. These studies evaluated safety in 1783 patients treated with FLOMAX capsules and 798 patients administered placebo. Table 1 summarizes the treatment-emergent adverse events that occurred in ≥ 2% of patients receiving either FLOMAX capsules 0.4 mg or 0.8 mg and at an incidence numerically higher than that in the placebo group during two 13-week U.S. trials (US92-03A and US93-01) conducted in 1487 men.

Table 1 : Treatment-Emergent1 Adverse Events Occurring in ≥ 2% of FLOMAX Capsules or Placebo Patients in Two U.S. Short-Term Placebo-Controlled Clinical Studies

BODY SYSTEM/ ADVERSE EVENT FLOMAX CAPSULES GROUPS 0.4 mg
n=502
0.8 mg
n=492
PLACEBO
n=493
BODY AS WHOLE
Headache 97 (19.3%) 104 (21.1%) 99 (20.1%)
Infection2 45 (9.0%) 53 (10.8%) 37 (7.5%)
Asthenia 39 (7.8%) 42 (8.5%) 27 (5.5%)
Back pain 35 (7.0%) 41 (8.3%) 27 (5.5%)
Chest pain 20 (4.0%) 20 (4.1%) 18 (3.7%)
NERVOUS SYSTEM
Dizziness 75 (14.9%) 84 (17.1%) 50 (10.1%)
Somnolence 15 (3.0%) 21 (4.3%) 8 (1.6%)
Insomnia 12 (2.4%) 7 (1.4%) 3 (0.6%)
Libido decreased 5 (1.0%) 10 (2.0%) 6 (1.2%)
RESPIRATORY SYSTEM
Rhinitis3 66 (13.1%) 88 (17.9%) 41 (8.3%)
Pharyngitis 29 (5.8%) 25 (5.1%) 23 (4.7%)
Cough increased 17 (3.4%) 22 (4.5%) 12 (2.4%)
Sinusitis 11 (2.2%) 18 (3.7%) 8 (1.6%)
DIGESTIVE SYSTEM
Diarrhea 31 (6.2%) 21 (4.3%) 22 (4.5%)
Nausea 13 (2.6%) 19 (3.9%) 16 (3.2%)
Tooth disorder 6 (1.2%) 10 (2.0%) 7 (1.4%)
UROGENITAL SYSTEM
Abnormal ejaculation 42 (8.4%) 89 (18.1%) 1 (0.2%)
SPECIAL SENSES
Blurred vision 1 (0.2%) 10 (2.0%) 2 (0.4%)
1A treatment-emergent adverse event was defined as any event satisfying one of the following criteria:
  • The adverse event occurred for the first time after initial dosing with double-blind study medication.
  • The adverse event was present prior to or at the time of initial dosing with double-blind study medication and subsequently increased in severity during double-blind treatment; or
  • The adverse event was present prior to or at the time of initial dosing with double-blind study medication, disappeared completely, and then reappeared during double-blind treatment.
2Coding preferred terms also include cold, common cold, head cold, flu, and flu-like symptoms.
3Coding preferred terms also include nasal congestion, stuffy nose, runny nose, sinus congestion, and hay fever.

Signs and Symptoms of Orthostasis

In the two U.S. studies, symptomatic postural hypotension was reported by 0.2% of patients (1 of 502) in the 0.4 mg group, 0.4% of patients (2 of 492) in the 0.8 mg group, and by no patients in the placebo group. Syncope was reported by 0.2% of patients (1 of 502) in the 0.4 mg group, 0.4% of patients (2 of 492) in the 0.8 mg group, and 0.6% of patients (3 of 493) in the placebo group. Dizziness was reported by 15% of patients (75 of 502) in the 0.4 mg group, 17% of patients (84 of 492) in the 0.8 mg group, and 10% of patients (50 of 493) in the placebo group. Vertigo was reported by 0.6% of patients (3 of 502) in the 0.4 mg group, 1% of patients (5 of 492) in the 0.8 mg group, and by 0.6% of patients (3 of 493) in the placebo group.

Multiple testing for orthostatic hypotension was conducted in a number of studies. Such a test was considered positive if it met one or more of the following criteria: (1) a decrease in systolic blood pressure of ≥ 20 mmHg upon standing from the supine position during the orthostatic tests; (2) a decrease in diastolic blood pressure ≥ 10 mmHg upon standing, with the standing diastolic blood pressure < 65 mmHg during the orthostatic test; (3) an increase in pulse rate of ≥ 20 bpm upon standing with a standing pulse rate ≥ 100 bpm during the orthostatic test; and (4) the presence of clinical symptoms (faintness, lightheadedness/lightheaded, dizziness, spinning sensation, vertigo, or postural hypotension) upon standing during the orthostatic test.

Following the first dose of double-blind medication in Study 1, a positive orthostatic test result at 4 hours post-dose was observed in 7% of patients (37 of 498) who received FLOMAX capsules 0.4 mg once daily and in 3% of the patients (8 of 253) who received placebo. At 8 hours post-dose, a positive orthostatic test result was observed for 6% of the patients (31 of 498) who received FLOMAX capsules 0.4 mg once daily and 4% (9 of 250) who received placebo (Note: patients in the 0.8 mg group received 0.4 mg once daily for the first week of Study 1).

In Studies 1 and 2, at least one positive orthostatic test result was observed during the course of these studies for 81 of the 502 patients (16%) in the FLOMAX capsules 0.4 mg once-daily group, 92 of the 491 patients (19%) in the FLOMAX capsules 0.8 mg once-daily group, and 54 of the 493 patients (11%) in the placebo group.

Because orthostasis was detected more frequently in FLOMAX capsule-treated patients than in placebo recipients, there is a potential risk of syncope [see WARNINGS AND PRECAUTIONS].

Abnormal Ejaculation

Abnormal ejaculation includes ejaculation failure, ejaculation disorder, retrograde ejaculation, and ejaculation decrease. As shown in Table 1, abnormal ejaculation was associated with FLOMAX capsules administration and was dose-related in the U.S. studies. Withdrawal from these clinical studies of FLOMAX capsules because of abnormal ejaculation was also dose-dependent, with 8 of 492 patients (1.6%) in the 0.8 mg group and no patients in the 0.4 mg or placebo groups discontinuing treatment due to abnormal ejaculation.

Laboratory Tests

No laboratory test interactions with FLOMAX capsules are known. Treatment with FLOMAX capsules for up to 12 months had no significant effect on prostate-specific antigen (PSA).

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of FLOMAX capsules. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Decisions to include these reactions in labeling are typically based on one or more of the following factors: (1) seriousness of the reaction, (2) frequency of reporting, or (3) strength of causal connection to FLOMAX capsules.

Allergic-type reactions such as skin rash, urticaria, pruritus, angioedema, and respiratory symptoms have been reported with positive rechallenge in some cases. Priapism has been reported rarely. Infrequent reports of dyspnea, palpitations, hypotension, atrial fibrillation, arrhythmia, tachycardia, skin desquamation including reports of Stevens-Johnson syndrome, erythema multiforme, dermatitis exfoliative, constipation, vomiting, visual impairment, and epistaxis have been received during the postmarketing period.

During cataract and glaucoma surgery, a variant of small pupil syndrome known as Intraoperative Floppy Iris Syndrome (IFIS) has been reported in association with alpha1 blocker therapy [see WARNINGS AND PRECAUTIONS].

Read the Flomax (tamsulosin hydrochloride) Side Effects Center for a complete guide to possible side effects

DRUG INTERACTIONS

Cytochrome P450 Inhibition

Strong and Moderate Inhibitors of CYP3A4 or CYP2D6

Tamsulosin is extensively metabolized, mainly by CYP3A4 and CYP2D6.

Concomitant treatment with ketoconazole (a strong inhibitor of CYP3A4) resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY]. The effects of concomitant administration of a moderate CYP3A4 inhibitor (e.g., erythromycin) on the pharmacokinetics of FLOMAX have not been evaluated [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].

Concomitant treatment with paroxetine (a strong inhibitor of CYP2D6) resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY]. A similar increase in exposure is expected in CYP2D6 poor metabolizers (PM) as compared to extensive metabolizers (EM). Since CYP2D6 PMs cannot be readily identified and the potential for significant increase in tamsulosin exposure exists when FLOMAX 0.4 mg is co-administered with strong CYP3A4 inhibitors in CYP2D6 PMs, FLOMAX 0.4 mg capsules should not be used in combination with strong inhibitors of CYP3A4 (e.g., ketoconazole) [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].

The effects of concomitant administration of a moderate CYP2D6 inhibitor (e.g., terbinafine) on the pharmacokinetics of FLOMAX have not been evaluated [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].

The effects of co-administration of both a CYP3A4 and a CYP2D6 inhibitor with FLOMAX capsules have not been evaluated. However, there is a potential for significant increase in tamsulosin exposure when FLOMAX 0.4 mg is co-administered with a combination of both CYP3A4 and CYP2D6 inhibitors [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].

Cimetidine

Treatment with cimetidine resulted in a significant decrease (26%) in the clearance of tamsulosin hydrochloride, which resulted in a moderate increase in tamsulosin hydrochloride AUC (44%) [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].

Other Alpha Adrenergic Blocking Agents

The pharmacokinetic and pharmacodynamic interactions between FLOMAX capsules and other alpha adrenergic blocking agents have not been determined; however, interactions between FLOMAX capsules and other alpha adrenergic blocking agents may be expected [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].

PDE5 Inhibitors

Caution is advised when alpha adrenergic blocking agents including FLOMAX are co-administered with PDE5 inhibitors. Alpha-adrenergic blockers and PDE5 inhibitors are both vasodilators that can lower blood pressure. Concomitant use of these two drug classes can potentially cause symptomatic hypotension [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].

Warfarin

A definitive drug-drug interaction study between tamsulosin hydrochloride and warfarin was not conducted. Results from limited in vitro and in vivo studies are inconclusive. Caution should be exercised with concomitant administration of warfarin and FLOMAX capsules [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].

Nifedipine, Atenolol, Enalapril

Dosage adjustments are not necessary when FLOMAX capsules are administered concomitantly with nifedipine, atenolol, or enalapril [see CLINICAL PHARMACOLOGY].

Digoxin And Theophylline

Dosage adjustments are not necessary when a FLOMAX capsule is administered concomitantly with digoxin or theophylline [see CLINICAL PHARMACOLOGY].

Furosemide

FLOMAX capsules had no effect on the pharmacodynamics (excretion of electrolytes) of furosemide. While furosemide produced an 11% to 12% reduction in tamsulosin hydrochloride Cmax and AUC, these changes are expected to be clinically insignificant and do not require adjustment of the FLOMAX capsules dosage [see CLINICAL PHARMACOLOGY].

Read the Flomax Drug Interactions Center for a complete guide to possible interactions

Last reviewed on RxList: 8/4/2014
This monograph has been modified to include the generic and brand name in many instances.

Side Effects
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