Testosterone-5-alpha-reductase inhibitors - ATC code: G04C B02

Dutasteride

Each capsule contains 0.5 mg dutasteride.

Capsules, soft. The capsules are opaque, yellow, oblong soft gelatin capsules marked with GX CE2.

Treatment of moderate to severe symptoms of benign prostatic hyperplasia (BPH).

Reduction in the risk of acute urinary retention (AUR) and surgery in patients with moderate to severe symptoms of BPH.

Avodart can be administered alone or in combination with the alpha-blocker tamsulosin (0.4mg).

Adults (including elderly):

The recommended dose of Avodart is one capsule (0.5 mg) taken orally once a day. The capsules should be swallowed whole and not chewed or opened as contact with the capsule contents may result in irritation of the oropharyngeal mucosa. The capsules may be taken with or without food. Although an improvement may be observed at an early stage, it can take up to 6 months before a response to the treatment can be achieved. No dose adjustment is necessary in the elderly.

Renal impairment

The effect of renal impairment on 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 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 dutasteride is contraindicated.

Not recommended.

No dose adjustment is necessary in the elderly.

Avodart is contraindicated in:

- women and children and adolescents.

- patients with hypersensitivity to dutasteride, other 5-alpha reductase inhibitors, soya, peanut or any of the other excipients.

- patients with severe hepatic impairment.

Combination therapy should be prescribed after careful benefit risk assessment due to the potential increased risk of adverse events and after consideration of alternative treatment options including monotherapies.

In a 4-year clinical study, the incidence of cardiac failure (a composite term of reported events, primarily cardiac failure and congestive cardiac failure) was higher among subjects taking the combination of Avodart and an alpha blocker tamsulosin, than it was among subjects not taking the combination. No causal relationship between Avodart (alone or in combination with an alpha blocker) and cardiac failure has been established.

Digital rectal examination, as well as other evaluations for prostate cancer, must be performed on patients with BPH prior to initiating therapy with Avodart and periodically thereafter.

Dutasteride is absorbed through the skin, therefore, women, children and adolescents must avoid contact with leaking capsules. If contact is made with leaking capsules, the contact area should be washed immediately with soap and water.

Dutasteride was not studied in patients with liver disease. Caution should be used in the administration of dutasteride to patients with mild to moderate hepatic impairment.

Serum prostate-specific antigen (PSA) concentration is an important component in the detection of prostate cancer. Generally, a total serum PSA concentration greater than 4 ng/mL (Hybritech) requires further evaluation and consideration of prostate biopsy. Physicians should be aware that a baseline PSA less than 4 ng/mL in patients taking Avodart does not exclude a diagnosis of prostate cancer. Avodart causes a decrease in serum PSA levels by approximately 50%, after 6 months, in patients with BPH, even in the presence of prostate cancer. Although there may be individual variation, the reduction in PSA by approximately 50% is predictable as it was observed over the entire range of baseline PSA values (1.5 to 10 ng/mL). Therefore to interpret an isolated PSA value in a man treated with Avodart for six months or more, PSA values should be doubled for comparison with normal ranges in untreated men. This adjustment preserves the sensitivity and specificity of the PSA assay and maintains its ability to detect prostate cancer. Any sustained increases in PSA levels while on Avodart should be carefully evaluated, including consideration of noncompliance to therapy with Avodart.

Total serum PSA levels return to baseline within 6 months of discontinuing treatment. The ratio of free to total PSA remains constant even under the influence of Avodart. If clinicians elect to use percent free PSA as an aid in the detection of prostate cancer in men undergoing Avodart therapy, no adjustment to its value appears necessary.

For information on the decrease of serum PSA levels during treatment with dutasteride and guidance concerning prostate cancer detection, please see Precautions.

Effects of other drugs on the pharmacokinetics of dutasteride

Use together with CYP3A4 and/or P-glycoprotein-inhibitors:

Dutasteride is mainly eliminated via metabolism. In vitro studies indicate that this metabolism is catalysed by CYP3A4 and CYP3A5. No formal interaction studies have been performed with potent CYP3A4 inhibitors. However, in a population pharmacokinetic study, dutasteride serum concentrations were on average 1.6 to 1.8 times greater, respectively, in a small number of patients treated concurrently with verapamil or diltiazem (moderate inhibitors of CYP3A4 and inhibitors of P-glycoprotein) than in other patients.

Long-term combination of dutasteride with drugs that are potent inhibitors of the enzyme CYP3A4 (e.g. ritonavir, indinavir, nefazodone, itraconazole, ketoconazole administered orally) may increase serum concentrations of dutasteride. Further inhibition of 5-alpha reductase at increased dutasteride exposure, is not likely. However, a reduction of the dutasteride dosing frequency can be considered if side effects are noted. It should be noted that in the case of enzyme inhibition, the long half-life may be further prolonged and it can take more than 6 months of concurrent therapy before a new steady state is reached.

Administration of 12g colestyramine one hour after a 5mg single dose of dutasteride did not affect the pharmacokinetics of dutasteride.

Effects of dutasteride on the pharmacokinetics of other drugs

Dutasteride has no effect on the pharmacokinetics of warfarin or digoxin. This indicates that dutasteride does not inhibit/induce CYP2C9 or the transporter P-glycoprotein. In vitro interaction studies indicate that dutasteride does not inhibit the enzymes CYP1A2, CYP2D6, CYP2C9, CYP2C19 or CYP3A4.

In a small study (N=24) of two weeks duration in healthy men, dutasteride (0.5 mg daily) had no effect on the pharmacokinetics of tamsulosin or terazosin. There was also no indication of a pharmacodynamic interaction in this study.

AVODART AS MONOTHERAPY

Approximately 19% of the 2167 patients who received dutasteride in the 2 year Phase III placebo-controlled trials developed adverse reactions during the first year of treatment. The majority of events were mild to moderate and occurred in the reproductive system. No change to the adverse event profile was apparent over a further 2 years in open-label extension studies.

The following table shows adverse reactions from controlled clinical trials and post-marketing experience. The listed adverse events from clinical trials are investigator-judged drug-related events (with incidence more than or equal to 1%) reported with a higher incidence in patients treated with dutasteride compared with placebo during the first year of treatment. Adverse events from post-marketing experience were identified from spontaneous post-marketing reports; therefore the true incidence is unknown:

AVODART IN COMBINATION WITH THE ALPHA-BLOCKER TAMSULOSIN

Data from 4 year CombAT Study, comparing dutasteride 0.5mg (n=1623) and tamsulosin 0.4mg (n=1611) once daily alone and in combination (n=1610) have shown that the incidence of any investigator-judged drug-related adverse event during the first, second, third and forth years of treatment respectively was 22%, 6%, 4% and 2% for dutasteride/tamsulosin combination therapy, 15%, 6 %. 3% and 2% for dutasteride monotherapy and 13%,5%, 2% and 2% for tamsulosin monotherapy. The higher incidence of adverse events in the combination therapy group in the first year of treatment was due to a higher incidence of reproductive disorders, specifically ejaculation disorders, observed in this group.

The following investigator-judged drug-related adverse events have been reported with an incidence of greater than or equal to 1% during the first year of treatment in the CombAT Study; the incidence of these events during the four years of treatment is shown in the table below:

^a Combination = dutasteride 0.5 mg once daily plus tamsulosin 0.4 mg once daily.

^b Includes breast tenderness and breast enlargement.

GlaxoSmithKline UK

(POM)

12 April 2012