Dutasteride and Tamsulosin

Uses

Dutasteride & Tamsulosin combination capsules are used for the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate.

Dutasteride and Tamsulosin is also used to associated treatment for these conditions: Benign Prostatic Hyperplasia (BPH), Symptomatic Benign Prostatic HyperplasiaBenign Prostatic Hyperplasia (BPH), Benign Prostatic Hypertrophy, Bladder Outlet Obstruction, Ureteral Calculus

How Dutasteride and Tamsulosin works

The 5α-reductase is a nuclear-bound steroid intracellular enzyme primarily located in the prostatic stromal cell that converts the androgen testosterone into the more active metabolite, 5α-dihydrotestosterone (DHT). DHT is considered to be the primary androgen playing a role in the initial development and subsequent enlargement of the prostate gland. It serves as the hormonal mediator for the hyperplasia upon accumulation within the prostate gland. DHT displays a higher affinity towards androgen receptors in the prostate gland compared to testosterone and by acting on the androgen receptors, DHT modulates genes that are responsible for cell proliferation. Responsible for the synthesis of approximately one-third of circulating DHT, type I 5α-reductase is predominant in the sebaceous glands of most regions of skin, including the scalp, and liver. The type II 5a-reductase isozyme is primarily found in the prostate, seminal vesicles, epididymides, and hair follicles as well as liver, and is responsible for two-thirds of circulating DHT. Due to its dual inhibition of both isoenzymes of 5α-reductase, dutasteride causes a near-complete suppression of DHT. Compared to a 70% reduction of serum DHT levels caused by finasteride, a near-complete suppression of serum DHT-more than 90% is seen with dutasteride.

By forming a stable complex with both type II and type II 5α-reductase, dutasteride inhibits its enzymatic action of converting testosterone to 5α-dihydrotestosterone (DHT), which is the androgen primarily responsible for the initial development and subsequent enlargement of the prostate gland. It is proposed that DHT is the principal androgen responsible for prostatic growth in later life-normal masculinization of the external genitalia and maturation of the prostate gland during development-thus reducing the serum DHT levels results in reduced prostatic volume and increased epithelial apoptosis. Dutasteride is a competitive and specific inhibitor of both Type I and Type II 5α-reductase isoenzymes and when evaluated under in vitro and in vivo conditions, the dissociation of the drug from the drug-enzyme complex is reported to be extremely slow. Dutasteride does not bind to the human androgen receptor.

Tamsulosin is a blocker of alpha-1A and alpha-1D adrenoceptors. About 70% of the alpha-1 adrenoceptors in the prostate are of the alpha-1A subtype. By blocking these adrenoceptors, smooth muscle in the prostate is relaxed and urinary flow is improved. The blocking of alpha-1D adrenoceptors relaxes the detrusor muscles of the bladder which prevents storage symptoms. The specificity of tamsulosin focuses the effects to the target area while minimizing effects in other areas.

Dosage

Dutasteride and Tamsulosin dosage

The recommended dosage is 1 capsule (0.5 mg Dutasteride and 0.4 mg Tamsulosin Hydrochloride) taken once daily approximately 30 minutes after the same meal each day.

The capsules should be swallowed whole and not chewed or opened. Contact with the contents of the capsule may result in irritation of the oropharyngeal mucosa.

Side Effects

Impotence, decreased libido, breast disorders (including breast enlargement and tenderness), ejaculation disorders, erectile dysfunction and dizziness etc. may occur. Again, infection, asthenia, back pain, chest pain, somnolence, insomnia, rhinitis, pharyngitis, cough, sinusitis, and diarrhea etc. may occur.

Toxicity

LD50 values

The estimated dermal LD50 of dutasteride in rabbits is > 2,000 mg/kg.

Overdose

In studies of volunteers receiving single doses of dutasteride up to 40 mg (which is 80 times the therapeutic dose) for 7 days, there were no reports of clinically significant adverse events. Low incidences of impotence, reduced libido, gynecomastia, and ejaculation disorder occurred significantly more often in dutasteride than placebo recipients. There are no known antidotes for dutasteride. In case of overdose, appropriate symptomatic and supportive treatment should be given.

Nonclinical Toxicology

In a 2-year carcinogenicity mouse study, there was an increased incidence of benign hepatocellular adenomas in female mice receiving 250 mg/kg/day. An increased incidence of Leydig cell hyperplasia was observed in male rats receiving doses of 7.5 mg/kg/day and greater. At tumorogenic doses, the luteinizing hormone (LH) levels in rats were increased by 167%. There was no demonstrated a genotoxic potential of dutasteride or its metabolites in a bacterial mutagenesis assay, a chromosomal aberration assay in CHO cells, and a micronucleus assay in rats. At much higher doses than the maximum recommended human dose (MRHD) in sexually mature male rats, dutasteride caused a dose- and time-dependent decrease in fertility, reduced cauda epididymal (absolute) sperm counts but not sperm concentration (at 50 and 500 mg/kg/day), reduced weights of the epididymis, prostate, and seminal vesicles, and microscopic changes in the male reproductive organs. At exposures 425- and 315-fold the expected clinical exposure of dutasteride in rats and dogs, respectively, there were some signs of non-specific, reversible, centrally-mediated toxicity without associated histopathological changes.

Pregnancy and Lactation

As DHT is a necessary hormone for the development of male genitalia, exposure to dutasteride in pregnant women bearing male fetuses may cause fetal harm. In animal reproduction and developmental toxicity studies, dutasteride inhibited normal development of external genitalia in male fetuses. Although it is not known whether dutasteride is excreted in human milk, the use of dutasteride in women of childbearing potential, including nursing women. In elderly patients, the half-life of dutasteride may increase. As the renal elimination of dutasteride is very minimal, the use of dutasteride in patients renal insufficiency is reported to be safe. There are no specific dosage adjustment recommendations for use in elderly patients or patients with renal impairment.

In the event of overdose, patients may experience hypotension and should lie down in a supine position to maintain blood pressure and heart rate. If further measures are required intravenous fluids should be considered. If further progression is required, vasopressors may be used and renal function should be monitored. Dialysis is unlikely to assist in treating overdose because tamsulosin is extensively protein bound.

The oral LD50 in rats is 650mg/kg.

Tamsulosin is not indicated for use in women and no studies have been performed in pregnancy, though animal studies have not shown fetal harm. Tamsulosin is excreted in the milk of rats but there is no available data on what the effect of this tamsulosin exposure may be. Animal studies have shown male and female rat fertility is affected by tamsulosin due to impairment of ejaculation and fertilization. In men, tamsulosin is associated with abnormal ejaculation. Tamsulosin is not mutagenic but may be carcinogenic at levels above the maximum recommended human dose. Female rats experience a slight increase in the rates of mammary gland fibroadenomas and adenocarcinomas.

Precaution

Dutasteride-Tamsulosin combination capsules are used with caution because it-

• Can occur orthostatic hypotension and syncope
• Reduces serum prostate-specific antigen (PSA) concentration by approximately 50%
• Do not use with strong inhibitors of cytochrome P450 (CYP) 3A4 (e.g. Ketoconazole)
• Exercise caution with concomitant use of PDE-5 inhibitors, as this may increase the risk of hypotension
• Drugs that contain Dutasteride, may increase the risk of high-grade prostate cancer
• Women who are pregnant or could become pregnant should not handle due to potential risk to a male fetus
• Advise patients about the possibility and seriousness of priapism
• Patients should not donate blood until 6 months after their last dose
• Intraoperative Floppy Iris Syndrome has been observed during cataract surgery after alpha adrenergic antagonist exposure
• Exercise caution with concomitant use of Warfarin

Interaction

Dutasteride-Tamsulosin combination capsules are used with caution because it-

• Can occur orthostatic hypotension and syncope
• Reduces serum prostate-specific antigen (PSA) concentration by approximately 50%
• Do not use with strong inhibitors of cytochrome P450 (CYP) 3A4 (e.g. Ketoconazole)
• Exercise caution with concomitant use of PDE-5 inhibitors, as this may increase the risk of hypotension
• Drugs that contain Dutasteride, may increase the risk of high-grade prostate cancer
• Women who are pregnant or could become pregnant should not handle due to potential risk to a male fetus
• Advise patients about the possibility and seriousness of priapism
• Patients should not donate blood until 6 months after their last dose
• Intraoperative Floppy Iris Syndrome has been observed during cataract surgery after alpha adrenergic antagonist exposure
• Exercise caution with concomitant use of Warfarin

Volume of Distribution

Dutasteride displays a large volume of distribution ranging from 300 to 500 L. Following daily oral administration of 0.5 mg dutasteride healthy subjects for 12 months, the semen dutasteride concentrations averaged 3.4 ng/mL (range: 0.4 to 14 ng/mL) with 11.5% of serum dutasteride concentrations being partitioned into semen.

16L after intravenous administration.

Elimination Route

Following oral administration of a single dose of 0.5 mg dutasteride, the peak serum concentrations were reached within 2 to 3 hours. Following daily oral administration of 0.5 mg dutasteride, the steady-state concentration of 40 ng/mL is expected to be achieved at 6 months following initial administration. In healthy subjects, the absolute bioavailability was 60%, ranging from 40% to 94%. While food intake reduced the maximum serum concentrations by 10 to 15%, food intake is reported to have a negligible effect on the bioavailability of the drug.

Oral tamsulosin is 90% absorbed in fasted patients. The area under the curve is 151-199ng/mL*hr for a 0.4mg oral dose and 440-557ng/mL*hr for a 0.8mg oral dose. The maximum plasma concentration is 3.1-5.3ng/mL for a 0.4mg oral dose and 2.5-3.6ng/mL for a 0.8mg oral dose. Taking tamsulosin with food increases the time to maximum concentration from 4-5 hours to 6-7 hours but increases bioavailability by 30% and maximum plasma concentration by 40-70%.

Half Life

The terminal elimination half-life of dutasteride is approximately 5 weeks at steady state. This long half-life accounts for the serum concentrations remaining detectable for up to 4 to 6 months after discontinuation of treatment.

The half life in fasted patients is 14.9±3.9 hours. The elimination half life is 5-7 hours and the apparent half life is 9 to 13 hours in healthy subjects. In patients who require tamsulosin, the apparent half life is 14-15 hours.

Clearance

In a study of healthy volunteers receiving single oral doses of dutasteride ranging from 0.01 to 40 mg, dutasteride displayed a low linear clearance of 0.58 L/h. The estimated inter-individual variability for the linear clearance was high.

2.88L/h.

Elimination Route

Dutasteride and its metabolites mainly undergo fecal excretion. About 1-15% of the dose is excreted as the unchanged parent compound, while 2-90% of the total dose is excreted in the form of dutasteride-related metabolites in the feces. Trace amounts of unchanged dutasteride, with less than 1%, can also be detected in the urine. Therefore, on average, the dose unaccounted for approximated 55%, with a range between 5% and 97%.

97% of an orally administered does is recovered in studies, which 76% in the urine and 21% in the feces after 168 hours. 8.7% of the dose is excreted as unmetabolized tamsulosin.

Pregnancy & Breastfeeding use

Tamsulosin & Dutasteride combination is contraindicated for use by women. There have been no studies to investigate the effect of Tamsulosin & Dutasteride combination on pregnancy, lactation and fertility. The following statements reflect the information available from studies with the individual components.

Fertility: Dutasteride has been reported to affect semen characteristics (reduction in sperm count, semen volume, and sperm motility) in healthy men. The possibility of reduced male fertility cannot be excluded. Effects of Tamsulosin Hydrochloride on sperm counts or sperm function have not been evaluated.

Pregnancy: As with other 5 alpha reductase inhibitors, Dutasteride inhibits the conversion of testosterone to dihydrotestosterone and may, if administered to a woman carrying a male foetus, inhibit the development of the external genitalia of the foetus. Small amounts of Dutasteride have been recovered from the semen in subjects receiving Dutasteride. It is not known whether a male foetus will be adversely affected if his mother is exposed to the semen of a patient being treated with Dutasteride. As with all 5 alpha reductase inhibitors, when the patient’s partner is or may potentially be pregnant it is recommended that the patient avoids exposure of his partner to semen by use of a condom. Administration of Tamsulosin Hydrochloride to pregnant female rats and rabbits showed no evidence of foetal harm.

Lactation: It is not known whether Tamsulosin or Dutasteride are excreted in human milk.

Contraindication

Tamsulosin-Dutasteride combination is contra-indicated in women and children and adolescents, patients with hypersensitivity to Dutasteride, other 5-alpha reductase inhibitors, Tamsulosin (including Tamsulosin- induced angio-edema), soya, peanut or any of other the excipients, patients with a history of orthostatic hypotension and patients with severe hepatic impairment.

Special Warning

Renal impairment: The effect of renal impairment on Tamsulosin-Dutasteride pharmacokinetics has not been studied. No adjustment in dosage is anticipated for patients with renal impairment.

Hepatic impairment: The effect of hepatic impairment on Tamsulosin-Dutasteride pharmacokinetics has not been studied so caution should be used in patients with mild to moderate hepatic impairment. In patients with severe hepatic impairment, the use of Tamsulosin & Dutasteride capsule is contraindicated.

Acute Overdose

No data are available with regard to over dosage of Tamsulosin-Dutasteride combination.

Storage Condition

Store in a cool and dry place, protected from light.

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