What is Dutasteride Made Of?
Dutasteride is a synthetic 4-azasteroid compound chemically designated as (5α,17β)-N-{2,5 bis(trifluoromethyl)phenyl}-3-oxo-4-azaandrost-1-ene-17-carboxamide with the molecular formula C27H30F6N2O2 and a molecular weight of 528.5. 1
Chemical Composition and Physical Properties
- Dutasteride appears as a white to pale yellow powder with a melting point of 242° to 250°C 1
- It is soluble in ethanol (44 mg/mL), methanol (64 mg/mL), and polyethylene glycol 400 (3 mg/mL), but is insoluble in water 1
- Each dutasteride capsule contains 0.5 mg of dutasteride dissolved in a mixture of mono-di-glycerides of caprylic/capric acid and butylated hydroxytoluene 1
Capsule Formulation Components
- Active ingredient: 0.5 mg dutasteride 1
- Inactive excipients in the capsule shell:
- Gelatin (from certified BSE-free bovine sources)
- Glycerin
- Medium chain triglycerides
- Opatint white (contains glycerin and titanium dioxide)
- Opatint yellow (contains ferric oxide yellow and glycerin)
- Soy lecithin 1
- Printing ink components:
- Ferric oxide red
- Isopropyl alcohol
- Propylene glycol
- Simethicone 1
Mechanism of Action
- Dutasteride is a selective inhibitor of both type 1 and type 2 isoforms of steroid 5 alpha-reductase, an intracellular enzyme that converts testosterone to dihydrotestosterone (DHT) 1
- Unlike finasteride which only inhibits the type 2 isoenzyme, dutasteride inhibits both isoenzymes, resulting in greater and more consistent DHT suppression 2, 3
- By inhibiting both isoenzymes, dutasteride treatment reduces serum DHT levels by >90% in most patients after 1 year of treatment 4
Clinical Significance
- Dutasteride is primarily used for treatment of benign prostatic hyperplasia (BPH) to improve symptoms and reduce the risk of acute urinary retention and BPH-related surgery 3
- It is also used off-label for male pattern baldness treatment, with some studies suggesting superior efficacy compared to finasteride in hair regrowth 5
- The medication affects PSA levels, typically causing a 50-60% reduction after 12 months of therapy, which must be considered when interpreting PSA results for prostate cancer screening 2
Adverse Effects
- Common side effects include sexual dysfunction (decreased libido, erectile dysfunction, ejaculation disorders) and gynecomastia 2, 6
- The sexual side effects tend to decrease over time with continued use 4
- Dutasteride can affect sperm parameters, with studies showing reductions in total sperm count (23%), semen volume (26%), and sperm motility (18%) after 52 weeks of treatment 1
Understanding the chemical composition and formulation of dutasteride is important for identifying potential allergies or contraindications, while recognizing its dual inhibition mechanism helps explain its clinical effects and potential advantages over single-isoenzyme inhibitors like finasteride.