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Release-modulating factors strongly affecting steroid diffusion from silicone elastomer.

Harold A Nash1, Dale N Robertson, Simone J Evans

  • 1Center for Biomedical Research, Population Council, 1230 York Avenue, New York, NY 10021, USA. hnash@popcbr.rockefeller.edu

Journal of Pharmaceutical Sciences
|September 7, 2004
PubMed
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Decreased release rates from levonorgestrel (LNG) implants were investigated. A key impurity, 6beta-hydroxy-levonorgestrel (6beta-OH-LNG), was identified as the cause, significantly reducing drug release.

Area of Science:

  • Pharmacology
  • Materials Science
  • Drug Delivery Systems

Background:

  • Levonorgestrel (LNG) implants are widely used for long-term contraception.
  • Over time, a decrease in the drug release rate from these implants has been observed.
  • The exact cause of this release rate modulation has not been fully elucidated.

Purpose of the Study:

  • To identify the factors responsible for the time-dependent decrease in release rate from LNG implants.
  • To understand the chemical nature of these release-modulating factors.
  • To assess the impact of identified factors on LNG release kinetics.

Main Methods:

  • Investigated changes in release rate after emptying and refilling implants.
  • Utilized fractional crystallization to isolate and concentrate release-modulating substances.

Related Experiment Videos

  • Analyzed LNG samples from different production lots using chemical methods.
  • Synthesized and tested the effect of identified compounds on LNG release.

    • Main Results:

    • Partial restoration of release rate was achieved by refilling implants with LNG.
    • Irrigating implant tubing with methanol prior to refilling further increased release rates.
    • Identified 6beta-hydroxy-levonorgestrel (6beta-OH-LNG) as a prominent release-modulating impurity.
    • 6beta-OH-LNG, when added to LNG at 2%, reduced the release rate by 27%.

    Conclusions:

    • The decrease in levonorgestrel release rate from implants is attributed to specific impurities.
    • 6beta-hydroxy-levonorgestrel is a significant factor that modulates and reduces LNG release.
    • Understanding these impurities is crucial for optimizing the long-term performance of LNG implants.