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Details with Side Effects
The signs and symptoms of orthostasis (postural hypotension, dizziness, and vertigo) were detected more frequently in FLOMAX capsule-treated patients than in placebo recipients. As with other alpha adrenergic blocking agents there is a potential risk of syncope [see ADVERSE REACTIONS]. Patients beginning treatment with FLOMAX capsules should be cautioned to avoid situations in which injury could result should syncope occur [see PATIENT INFORMATION].
Tamsulosin is extensively metabolized, mainly by CYP3A4 and CYP2D6. FLOMAX capsules 0.4 mg should not be used in combination with strong inhibitors of CYP3A4 (e.g., ketoconazole) [see DRUG INTERACTIONS and CLINICAL PHARMACOLOGY]. FLOMAX capsules should be used with caution in combination with moderate inhibitors of CYP3A4 (e.g., erythromycin), in combination with strong (e.g., paroxetine) or moderate (e.g., terbinafine) inhibitors of CYP2D6, in patients known to be CYP2D6 poor metabolizers particularly at a dose higher than 0.4 mg (e.g., 0.8 mg) [see DRUG INTERACTIONS and CLINICAL PHARMACOLOGY].
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 DRUG INTERACTIONS and CLINICAL PHARMACOLOGY].
Rarely (probably less than 1 in 50,000 patients), tamsulosin, like other alpha1 antagonists, has been associated with priapism (persistent painful penile erection unrelated to sexual activity). Because this condition can lead to permanent impotence if not properly treated, patients must be advised about the seriousness of the condition [see PATIENT INFORMATION].
Screening for Prostate Cancer
Prostate cancer and BPH frequently co-exist; therefore, patients should be screened for the presence of prostate cancer prior to treatment with FLOMAX capsules and at regular intervals afterwards [see PATIENT INFORMATION].
Intraoperative Floppy Iris Syndrome
Most reports were in patients taking the alpha1 blocker when IFIS occurred, but in some cases, the alpha1 blocker had been stopped prior to surgery. In most of these cases, the alpha1 blocker had been stopped recently prior to surgery (2 to 14 days), but in a few cases, IFIS was reported after the patient had been off the alpha1 blocker for a longer period (5 weeks to 9 months). IFIS is a variant of small pupil syndrome and is characterized by the combination of a flaccid iris that billows in response to intraoperative irrigation currents, progressive intraoperative miosis despite preoperative dilation with standard mydriatic drugs and potential prolapse of the iris toward the phacoemulsification incisions. The patient's ophthalmologist should be prepared for possible modifications to their surgical technique, such as the utilization of iris hooks, iris dilator rings, or viscoelastic substances.
IFIS may increase the risk of eye complications during and after the operation. The benefit of stopping alpha1 blocker therapy prior to cataract surgery has not been established. The initiation of therapy with tamsulosin in patients for whom cataract surgery is scheduled is not recommended.
In patients with sulfa allergy, allergic reaction to FLOMAX capsules has been rarely reported. If a patient reports a serious or life-threatening sulfa allergy, caution is warranted when administering FLOMAX capsules.
Patient Counseling Information
See FDA-Approved Patient Labeling
Patients should be told about the possible occurrence of symptoms related to postural hypotension, such as dizziness, when taking FLOMAX capsules, and they should be cautioned about driving, operating machinery, or performing hazardous tasks [see WARNINGS AND PRECAUTIONS].
Patients should be advised about the possibility of priapism as a result of treatment with FLOMAX capsules and other similar medications. Patients should be informed that this reaction is extremely rare, but if not brought to immediate medical attention, can lead to permanent erectile dysfunction (impotence) [see WARNINGS AND PRECAUTIONS].
Screening for Prostate Cancer
Prostate cancer and BPH frequently co-exist; therefore, patients should be screened for the presence of prostate cancer prior to treatment with FLOMAX capsules and at regular intervals afterwards [see WARNINGS AND PRECAUTIONS].
Intraoperative Floppy Iris Syndrome
Patients considering cataract surgery should be advised to tell their ophthalmologist that they have taken FLOMAX capsules [see WARNINGS AND PRECAUTIONS].
Patients should be advised not to crush or chew the FLOMAX capsules.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Rats administered doses up to 43 mg/kg/day in males and 52 mg/kg/day in females had no increases in tumor incidence, with the exception of a modest increase in the frequency of mammary gland fibroadenomas in female rats receiving doses ≥ 5.4 mg/kg (P < 0.015). The highest doses of tamsulosin hydrochloride evaluated in the rat carcinogenicity study produced systemic exposures (AUC) in rats 3 times the exposures in men receiving the maximum therapeutic dose of 0.8 mg/day.
Mice were administered doses up to 127 mg/kg/day in males and 158 mg/kg/day in females. There were no significant tumor findings in male mice. Female mice treated for 2 years with the two highest doses of 45 and 158 mg/kg/day had statistically significant increases in the incidence of mammary gland fibroadenomas (P < 0.0001) and adenocarcinomas (P < 0.0075). The highest dose levels of tamsulosin hydrochloride evaluated in the mice carcinogenicity study produced systemic exposures (AUC) in mice 8 times the exposures in men receiving the maximum therapeutic dose of 0.8 mg/day.
The increased incidences of mammary gland neoplasms in female rats and mice were considered secondary to tamsulosin hydrochloride-induced hyperprolactinemia. It is not known if FLOMAX capsules elevate prolactin in humans. The relevance for human risk of the findings of prolactin-mediated endocrine tumors in rodents is not known.
Tamsulosin hydrochloride produced no evidence of mutagenic potential in vitro in the Ames reverse mutation test, mouse lymphoma thymidine kinase assay, unscheduled DNA repair synthesis assay, and chromosomal aberration assays in Chinese hamster ovary cells or human lymphocytes. There were no mutagenic effects in the in vivo sister chromatid exchange and mouse micronucleus assay.
Studies in rats revealed significantly reduced fertility in males dosed with single or multiple daily doses of 300 mg/kg/day of tamsulosin hydrochloride (AUC exposure in rats about 50 times the human exposure with the maximum therapeutic dose). The mechanism of decreased fertility in male rats is considered to be an effect of the compound on the vaginal plug formation possibly due to changes of semen content or impairment of ejaculation. The effects on fertility were reversible, showing improvement by 3 days after a single dose and 4 weeks after multiple dosing. Effects on fertility in males were completely reversed within nine weeks of discontinuation of multiple dosing. Multiple doses of 10 and 100 mg/kg/day tamsulosin hydrochloride (1/5 and 16 times the anticipated human AUC exposure) did not significantly alter fertility in male rats. Effects of tamsulosin hydrochloride on sperm counts or sperm function have not been evaluated.
Studies in female rats revealed significant reductions in fertility after single or multiple dosing with 300 mg/kg/day of the R-isomer or racemic mixture of tamsulosin hydrochloride, respectively. In female rats, the reductions in fertility after single doses were considered to be associated with impairments in fertilization. Multiple dosing with 10 or 100 mg/kg/day of the racemic mixture did not significantly alter fertility in female rats.
Use In Specific Populations
Teratogenic Effects - Pregnancy Category B
Administration of tamsulosin hydrochloride to pregnant female rats at dose levels up to approximately 50 times the human therapeutic AUC exposure (300 mg/kg/day) revealed no evidence of harm to the fetus. Administration of tamsulosin hydrochloride to pregnant rabbits at dose levels up to 50 mg/kg/day produced no evidence of fetal harm. FLOMAX capsules are not indicated for use in women.
FLOMAX capsules are not indicated for use in women.
FLOMAX capsules are not indicated for use in pediatric populations.
Efficacy and positive benefit/risk of tamsulosin hydrochloride was not demonstrated in two studies conducted in patients 2 years to 16 years of age with elevated detrusor leak point pressure ( > 40 cm H2O) associated with known neurological disorder (e.g., spina bifida). Patients in both studies were treated on a weight-based mg/kg schema (0.025 mg, 0.05 mg, 0.1 mg, 0.2 mg, or 0.4 mg tamsulosin hydrochloride) for the reduction in detrusor leak point pressure below 40 cm H2O. In a randomized, double-blind, placebo-controlled, 14-week, pharmacokinetic, safety and efficacy study in 161 patients, no statistically significant difference in the proportion of responders was observed between groups receiving tamsulosin hydrochloride and placebo. In an open-label, 12-month safety study, 87 patients were treated with tamsulosin hydrochloride. The most frequently reported adverse events ( ≥ 5%) from the pooled data of both studies were urinary tract infection, vomiting, pyrexia, headache, nasopharyngitis, cough, pharyngitis, influenza, diarrhea, abdominal pain, and constipation.
Of the total number of subjects (1783) in clinical studies of tamsulosin, 36% were 65 years of age and over. No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and the other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out [see CLINICAL PHARMACOLOGY].
Patients with renal impairment do not require an adjustment in FLOMAX capsules dosing. However, patients with end-stage renal disease (CLcr < 10 mL/min/1.73 m²) have not been studied [see CLINICAL PHARMACOLOGY].
Patients with moderate hepatic impairment do not require an adjustment in FLOMAX capsules dosage. FLOMAX has not been studied in patients with severe hepatic impairment [see CLINICAL PHARMACOLOGY].
Last reviewed on RxList: 8/8/2011
This monograph has been modified to include the generic and brand name in many instances.
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