Avodart [Dutasteride], marketed by GSK, is a 5-alpha-reductase inhibitor used in the treatment of benign prostatic hypertrophy in men with enlarged prostate. Avodart [Dutasteride], blocks the action of the 5-alpha-reductase enzymes that convert testosterone into dihydrotestosterone (DHT)
Avodart [Dutasteride], marketed by GSK, is a 5-alpha-reductase inhibitor used
in the treatment of benign prostatic hypertrophy in men with enlarged prostate.
Avodart [Dutasteride], blocks the action of the 5-alpha-reductase enzymes that
convert testosterone into dihydrotestosterone (DHT). Avodart [Dutasteride]
inhibits both isoforms of 5-alpha reductase [Type 1 and Type 2] unlike
finasteride, a drug belonging to the same class of drugs but inhibiting only
one form of 5-alpha reductase. It is a competitive and specific inhibitor of
5-alpha-reductase enzyme.
Avodart [Dutasteride] helps improve urinary flow and may also reduce for a
prostatic surgery later on.
It also helps in decreasing the chances of carcinoma prostate.
Benign Prostate Hypertrophy:
Benign prostate hypertrophy also known as benign enlargement of prostate is a
condition seen in middle aged men and elder men in which there is increase in
the size of prostate.
There is hyperplasia of prostatic stromal cells and epithelial cells leading to
formation of large nodules in the peri-urethral area of the prostate.
Hence if these nodules are large enough then they can suppress the urethral
canal completely or partially leading to obstruction in urine flow leading to
- urinary hesitancy,
- frequent urination
- increased risk of urinary tract infections due to stasis of bacteria in the
bladder residue
- incomplete voiding
- Post-urination dribble
- Nocturia– need to urinate during the night
- Intermittency
- Dysuria: painful urination
- weak urinary stream,
- straining
- Urinary retention which may be acute [inability to void] or chronic in which
there is gradual increase in the residual urinary volume, distending the
bladder. This may lead to renal failure termed as obstructive uropathy.
- Urinary bladder stone formation.
Dihydrotestosterone, a metabolite of testosterone plays a critical role in the
growth of prostate. Dihydrotestosterone is synthesized under the action of the
enzyme 5α-reductase, type 2 in the prostate from the circulating testosterone.
Since this enzyme is localized primarily in the stromal cells; hence, these
cells are the main site for the synthesis of dihydrotestosterone.
Although all men show prostate hypertrophy as they age, especially after 70
years, the incidence of symptomatic prostatic hypertrophy is observed more in
men have a western lifestyle than in men from rural areas.
Benign hypertrophy of prostate is associated with increased levels of serum
‘prostate specific antigen [PSA]’ which is a marker for carcinoma prostate, it
is not considered to be a pre-malignant condition.
This condition is diagnosed mainly by rectal examination and by
ultrasonography.
Indications and dosage:
Indications:
- Monotherapy: Symptomatic treatment of benign prostatic hyperplasia in men
with enlarged prostate by improving symptoms, reducing the risk of acute
retention of urine and reduce the risk of benign prostatic hyperplasia related
surgery.
- In combination with an alpha blocker: Avodart [Dutasteride] along with
tamsulosin is indicated for the treatment of symptomatic BPH in men with an
enlarged prostate.
- Clinical trials for dutasteride as a hair loss drug were undertaken, but
called off in late 2002. Industry sources speculate that Avodart would have
been seen as too similar to Propecia to have proved profitable as a hair loss
treatment. However, phase II results indicated that dutasteride 2.5mg generated
a superior hair count to finasteride 5mg at 12 and 24 weeks. Phase III trials
have been started in Korea,
however the future of this drug for male pattern baldness depends upon the
clearance by the FDA.
Avodart [Dutasteride] is used to treat urinary symptoms of Enlarging Prostate,
and to reduce the risk of acute urinary retention (AUR) and prostate surgery.
Dosage: available in capsule form of 0.5 mg each
- Monotherapy : the recommended daily dose of Avodart [Dutasteride] is 0.5mg
- Along with an alpha blocker: the recommended dose is Avodart [Dutasteride]
0.5 mg once daily and tamsulosin 0.4 mg once daily.
- Special precautions:
- presence of other urological disorders: especially carcinoma prostate
- Blood donation: patients who were on Avodart [Dutasteride] should refrain
from donating blood for 6 months since there is a possibility of the blood
being transfused to a pregnant female who might be carrying a male fetus.
- There have not been conclusive studies in the event of taking Avodart
[Dutasteride] in the presence of hepatic failure or renal failure. This drug is
highly metabolized in the liver and hence advisable to be avoided in hepatic
failure.
- Avodart [Dutasteride] can be used safely in geriatric population.
- Avodart [Dutasteride] is secreted in the semen. It does not alter the sperm
concentration and sperm morphology. However the clinical significance of its
effect on semen characteristics for an individual patient's fertility is not
known.
Contraindications:
- Patients who present with hypersensitivity to Avodart [Dutasteride] or other
5 alpha reductase inhibitors.
- Pregnancy: Dutasteride inhibits the activity of 5α-reductase, which prevents
conversion of testosterone to dihydrotesterone which is necessary for normal
development of male genitalia. Hence male fetuses of pregnant females taking
Avodart [Dutasteride] are at increased risk of abnormal external genitalia. It
is advised that pregnant females should not even touch the capsule of Avodart
[Dutasteride] since it is speculated that there may be some absorption through
skin. The contact area should be immediately washed with soap and water.
- Women of child bearing age
- Children
Side Effects:
On Monotherapy:
- impotence
- decreased libido
- ejaculatory defects
- Breast disorders (like breast enlargement and tenderness)
Long-Term Treatment (Up to 4 Years): Long term treatment with Avodart
[Dutasteride] is not found to be associated increased incidence of drug-related
sexual adverse reactions (impotence, decreased libido, and ejaculation
disorder) or breast disorders. No relationship between long-term use of Avodart
[Dutasteride] and male breast neoplasia has been found out till date.
In combination with alpha blocker tamsulosin:
- impotence
- decreased libido
- defect in ejaculation
- breast disorders (like breast enlargement and tenderness)
- dizziness
Hypersensitivity reactions like uritacaria, rash, pruritis, angioneurotic
edema, etc.
Drug interactions:
- Calcium Channel Antagonists: they decrease the clearance of Avodart
[Dutasteride]
- HIV /AIDS medicine such as nelfinavir or ritonavir
- Antibiotics such as clarithromycin, erythromycin, itraconazole, ketoconazole,
or troleandomycin.
- Selective serotonin reuptake inhibitor like fluoxetine, fluvoxamine, or
paroxetine
- tricyclic antidepressant such as amitriptyline, amoxapine, clomipramine,
desipramine, doxepin, imipramine, nortriptyline, protriptyline, or trimipramine