From the Guidelines
Oral finasteride is approximately 65% absorbed systemically after ingestion, with peak blood levels reached within 1-2 hours, and its effects on hormone levels can persist for several days to weeks after discontinuation due to irreversible enzyme inhibition. When considering the absorption and storage of oral finasteride, it's crucial to understand the pharmacokinetics and pharmacodynamics of the drug. The medication is well absorbed, with about 65% of the dose entering the bloodstream, and it reaches peak levels within a short timeframe 1. The key aspects of finasteride's pharmacology include:
- Peak blood levels are achieved within 1-2 hours of ingestion
- The drug has a half-life of approximately 5-6 hours in men under 70 years old
- Finasteride binds irreversibly to the 5-alpha reductase enzyme, leading to a persistent effect on dihydrotestosterone (DHT) levels
- DHT levels are reduced by about 65-70% with the 1mg dose and up to 85-90% with the 5mg dose
- The medication does not significantly accumulate in body tissues over time, but its hormonal effects can last for several days to weeks after discontinuation
- Finasteride is primarily metabolized in the liver and excreted through both urine and feces Given the information from the study 1, it's essential to consider the clinical implications of finasteride's systemic absorption, particularly in relation to its effects on prostate cancer and mortality, where the evidence suggests a reduction in prostate cancer incidence but with concerns about high-grade cancers.
From the FDA Drug Label
Absorption In a study of 15 healthy young subjects, the mean bioavailability of finasteride 5-mg tablets was 63% (range 34 to 108%), based on the ratio of area under the curve (AUC) relative to an intravenous (IV) reference dose. Distribution Mean steady-state volume of distribution was 76 liters (range, 44 to 96 liters). Approximately 90% of circulating finasteride is bound to plasma proteins.
The amount of oral finasteride that is actually absorbed and stored systemically is 63% of the dose, with a mean steady-state volume of distribution of 76 liters. Approximately 90% of circulating finasteride is bound to plasma proteins 2.
From the Research
Absorption and Storage of Oral Finasteride
- The provided studies do not directly address the question of how much oral finasteride is absorbed and stored systemically 3, 4, 5, 6, 7.
- The studies focus on the efficacy and safety of finasteride in treating benign prostatic hyperplasia (BPH) and its effects on prostate cancer risk, rather than its pharmacokinetics.
- There is no information available in the provided studies on the absorption and storage of oral finasteride, making it impossible to determine the exact amount absorbed and stored systemically.
Related Information
- Finasteride is a 5-alpha-reductase inhibitor used to treat BPH and reduce the risk of prostate cancer 3, 4, 5.
- The drug has been shown to decrease prostate volume and improve symptoms of BPH, as well as reduce the risk of low-grade prostate cancer 4, 5.
- However, the studies do not provide information on the pharmacokinetics of finasteride, including its absorption and storage in the body 3, 4, 5, 6, 7.