Finasteride is a medication frequently used to address pattern hair loss. Many individuals considering topical formulations often inquire whether the active compound is absorbed into the bloodstream. Understanding this absorption is important for those exploring hair loss treatment options. This article explores systemic absorption of topical finasteride.
What “Systemic Absorption” Means for Medications
When a medication is applied topically, it is intended to act primarily at the site of application. However, some portion of the drug can pass through the skin layers and enter the bloodstream, a process known as systemic absorption. Once in the bloodstream, the medication circulates throughout the body, potentially affecting areas beyond the localized application site.
In contrast, an oral drug is absorbed directly into the bloodstream from the digestive system, leading to widespread distribution. The goal with topical medications is often to maximize local effect while minimizing systemic exposure. Various factors, including the drug’s properties and skin condition, influence systemic absorption.
The Evidence: Does Topical Finasteride Go Systemic?
Scientific studies confirm topical finasteride undergoes some systemic absorption after scalp application. However, this absorption is significantly less than with oral finasteride. Research indicates approximately 1-5% of the applied topical dose may enter the bloodstream, leading to plasma concentrations over 100 times lower than oral finasteride.
For example, topical finasteride plasma concentrations are around 48.0 pg/mL, compared to approximately 5029 pg/mL for oral finasteride after 24 weeks. While topical finasteride reduces scalp DHT, its impact on serum (blood) DHT is less pronounced than oral finasteride. Studies show serum DHT reductions of 25-50% with topical formulations, versus around 70% with oral administration. Even small amounts of finasteride in the bloodstream can still reduce systemic DHT, given the drug’s potency.
Implications of Systemic Absorption
Reduced systemic absorption of topical finasteride diminishes the potential for systemic side effects. This is a primary reason many consider it an alternative to the oral tablet.
Minimal absorption contributes to the drug’s efficacy by influencing DHT levels in the scalp and, to a lesser extent, systemically. Clinical trials show topical finasteride is effective in improving hair count, with results often comparable to oral finasteride but with less systemic exposure. This balance between local effect and reduced systemic impact is important for its use.
Minimizing Systemic Exposure and Maximizing Local Effect
Several factors influence systemic absorption of topical finasteride, offering ways to minimize unwanted exposure. Lower concentrations (e.g., 0.05-0.1%) generally lead to less systemic absorption. The formulation’s vehicle also affects penetration, with solutions often penetrating better than gels.
Skin condition is another factor, as damaged or irritated skin can increase absorption. Applying the medication to a dry scalp, avoiding application immediately after showering, and using small amounts (e.g., 0.5-1mL) can help limit systemic uptake. Adhering to the prescribed dosage and application method, including frequency, is important to optimize local effect while keeping systemic absorption low.