Finasteride (Propecia) Flashcards

Drug Class

• Finasteride is classified as a 5-alpha reductase inhibitor and an alopecia agent.

Uses

• Commonly prescribed for Benign Prostatic Hypertrophy (BPH) and Male Pattern Alopecia.

Administration

• Administered orally; can be taken with or without food.
• Pregnant women should avoid handling crushed/broken tablets due to possible absorption risks to a male fetus.

Dosage Adjustments

• No dosage adjustments needed for chronic renal impairment or geriatric patients.

Contraindications

• Hypersensitivity to any component is a contraindication.
• Not indicated during pregnancy, whether known or suspected.

Precautions

• Use with caution in cases of hepatic impairment; finasteride is extensively metabolized.
• Potentially increased risk of high-grade prostate cancer reported.
• Serum PSA levels may decrease; regular monitoring recommended.
• Not indicated for pediatric or female patients.

Adverse Effects

• Common: Abnormal ejaculation (1.2% to 7.2%), breast tenderness (0.4% to 0.7%), reduced libido (1.8% to 10%).
• Serious: Potential neoplasms in the male breast and high-grade prostate cancer (1.8%).

Pregnancy Category

• Category X, indicating significant risks during pregnancy.

Monitoring

• A reduction in baseline PSA concentration by approximately 50% within 6 months indicates efficacy.
• Improvements in BPH symptoms (e.g., urinary flow and volume) also signal effectiveness.
• Monitor PSA periodically after setting a new baseline at least 6 months post-initiation.
• Regular checks for prostate cancer and other urological issues, especially in high-risk patients.

Mechanism of Action (MOA)

• Finasteride inhibits the activity of 5-alpha reductase type 2, preventing the conversion of testosterone to dihydrotestosterone (DHT).
• This reduction in DHT levels helps alleviate prostate enlargement in BPH and disrupts male-pattern balding in alopecia.

Pharmacokinetics

• Absorption: Peak concentration (Tmax) occurs within 1.3 to 1.8 hours; bioavailability is approximately 65% to 63% based on the tablet dosage.
• Distribution: Volume of distribution is 76 L with 90% protein binding.
• Metabolism: Extensively processed in the liver via the CYP3A4 pathway, yielding active metabolites.
• Excretion: Roughly 57% is eliminated through feces and 39% through urine as metabolites.
• Elimination half-life ranges from 4.5 to 8.2 hours based on age.

Medication Counseling

• Advise pregnant women to avoid contact with crushed or broken tablets.
• Inform patients of potential side effects such as erectile dysfunction and lowered libido.
• Encourage immediate reporting of breast changes, such as lumps or tenderness.
• Clarify that hair loss treatment benefits may take 3 months or longer to notice.