Dutasteride and tamsulosin (Jalyn): A combination of dutasteride, a 5α-reductase inhibitor, and tamsulosin, an alpha-adrenergic antagonist for the treatment of symptomatic benign prostatic hyperplasia

Dutasteride 0.5 mg and tamsulosin hydrochloride 0.4 mg capsules were approved by FDA for the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate. Dutasteride, a 5α-reductase inhibitor, inhibits the conversion of testosterone to dihydrotestosterone, the androgen primarily responsible for enlargement of the prostate gland. Tamsulosin acts primarily as an alpha 1-receptor-blocking agent. Blockade of these receptors causes smooth muscles in the bladder neck and prostate to relax, resulting in an improvement in urine flow rate and a reduction in BPH symptoms.

Efficacy. The efficacy of dutasteride and tamsulosin was evaluated in the multicenter, randomized, double-blind, parallel group study dubbed CombAT (or Combination of Avodart and Tamsulosin). The CombAT trial enrolled 4,844 men aged ≥50 years who had a serum prostate-specific antigen (PSA) ≥1.5 ng/mL and <10 ng/mL and diagnosed BPH, including enlarged prostate (≥30 cc) and BPH symptoms that were moderate-to-severe according to the International Prostate Symptom Score (IPSS). Patients were randomly assigned to receive co-administration of dutasteride 0.5 mg/d and tamsulosin hydrochloride 0.4 mg/d (n=1,610) compared with dutasteride alone (n=1,623) or tamsulosin alone (n=1,611). After 2 years of treatment, the mean changes from baseline (±SD) in IPSS symptom scores were –6.2 (±7.14) for the co-administration group, –4.9 (±6.81) for dutasteride, and –4.3 (±7.01) for tamsulosin, with a mean difference between co-administration and dutasteride of –1.3 units (P<.001; [95% CI, –1.69 to –0.86]), and between co-administration and tamsulosin of –1.8 units (P<.001; [95% CI, –2.23 to –1.40]). In addition, maximum urinary flow rate was improved to a greater extent with co-administration compared with each of the monotherapies (P≤.003 for all) and prostate volume was decreased with co-administration compared with tamsulosin alone (P<.001).

Safety. The most common adverse reactions when co-administering dutasteride and tamsulosin (occurring in ≥1% of treated patients) included impotence, decreased libido, breast enlargement and tenderness, ejaculation disorders, and dizziness. More serious adverse reactions associated with dutasteride and tamsulosin included orthostatic hypotension and/or syncope, especially when the combination is co-administered with an alpha-blocker or a phosphodiesterase-5 inhibitor (eg, sildenafil). Dutasteride and tamsulosin use can reduce total serum PSA concentration by approximately 50%, potentially masking detection of prostate cancer.