From the Guidelines
The half-life of topical bioidentical progesterone concentrations is not explicitly stated in the provided evidence, but based on general knowledge, it is approximately 24-48 hours in the bloodstream after application to the skin. When applied topically, progesterone cream is absorbed through the skin, enters the bloodstream, and distributes to target tissues. The relatively long half-life allows for once or twice daily dosing regimens, typically 20-40 mg per application depending on the specific formulation and clinical indication.
- Absorption rates can vary based on application site, with thinner skin areas like the inner wrists, inner arms, or neck providing better absorption than thicker skin areas.
- The lipophilic nature of progesterone allows it to be stored in adipose tissue, which contributes to its extended half-life compared to oral administration 1.
- This storage effect creates a reservoir that helps maintain more stable hormone levels over time.
- Factors that can affect the half-life include individual metabolism, skin thickness, blood flow to the application site, and the specific carrier base used in the formulation.
- For optimal effectiveness, it's essential to rotate application sites and follow a consistent application schedule, as noted in the context of menopausal hormone therapy 1.
- However, it is crucial to note that the use of compounded bioidentical hormones is not recommended due to the lack of evidence supporting their safety and effectiveness 1.
From the Research
Half-Life of Topical Bioidentical Progesterone Concentrations
- The half-life of topical bioidentical progesterone concentrations is not directly stated in the provided studies 2, 3, 4, 5, 6.
- However, a study on the transdermal delivery of bioidentical progesterone using dutasteride (a 5α-reductase inhibitor) measured serum and salivary progesterone levels over 12 hours 5.
- The study found that the average serum progesterone concentration was 1.40 ng/ml and 1.15 ng/ml in the progesterone and dutasteride groups, respectively, after 2 weeks of treatment 5.
- Salivary progesterone concentrations were increased by seven fold, from 0.40 ng/ml to 2.9 ng/ml, and were four times the serum levels 5.
- Another study evaluated the efficacy of bioidentical progesterone cream in the treatment of menopause-related vasomotor symptoms, but did not report on the half-life of topical bioidentical progesterone concentrations 6.
Pharmacokinetics of Topical Bioidentical Progesterone
- A study on the effectiveness of sublingual and topical compounded bioidentical hormone replacement therapy in postmenopausal women found that topical therapy did not improve symptoms as extensively or rapidly as sublingual therapy 4.
- The study suggests that the pharmacokinetics of topical bioidentical progesterone may be different from those of sublingual progesterone, which could affect the half-life of topical bioidentical progesterone concentrations 4.
- Further research is needed to determine the half-life of topical bioidentical progesterone concentrations and to fully understand its pharmacokinetics 2, 3, 4, 5, 6.