Characterisation of progestins used in hormonal contraception and progesterone via the progesterone receptor.

Different progestogens are widely used in hormonal therapy and mediate their therapeutic actions via the progesterone receptor (PR). Little published data exist on their relative efficacies and potencies via the PR, while those available may be confounded by off-target receptors, different methodologies and model systems. We performed dose-response analysis to investigate the efficacies and potencies for transcription of progesterone and several progestins widely used in contraception via the B isoform of human PR (PR-B). We compared responses using three different cell lines and two different transient transfection conditions. Results show that in vitro biological responses via PR-B for the select progestogens can vary significantly in biocharacter, rank order and absolute values for efficacies and potencies, depending on the cell line and transfection condition. Progestogen rank orders for published relative binding affinities are mostly different to those for relative efficacies and potencies. These in vitro differences suggest that rank orders and absolute values of the efficacies and potencies of the progestogens are likely to vary in vivo in a cell-specific and progestogen-specific manner, and cannot easily be extrapolated from in vitro data, as is usually the practice. While obtaining such data in vivo is not possible, these in vitro data show proof of concept for likely significant cell- and progestogen-specific PR-B effects.

Forced degradation studies of medroxyprogesterone acetate injectable suspensions (150 mg/ml) with implementation of HPLC, mass spectrometry, and QSAR techniques.

Medroxyprogesterone acetate (MPA) injectable products are a key commodity for reproductive health and are available in the global market from a variety of manufacturing sources. Depending on the climatic zone conditions of the destination country for product use, MPA injectables are at risk of exposure to adverse transport and storage conditions. Analytical methods are available that quantify impurity levels in MPA and MPA injectable products, but minimal information is publicly available on the source of impurity and degradation product generation or the safety risk of these compounds. Forced degradation studies were conducted on MPA and MPA injectables to gain a better understanding of potential sources of impurities and degradation products. Furthermore, QSAR analysis was conducted to assess the toxicity risk of known impurities. More impurities were generated under acidic, basic, light, and oxidative forced degradation conditions relative to thermal degradation, however thermal exposure is the most likely adverse condition to be experienced by these products. Even if impurities are present in MPA injectables, QSAR analysis found that known impurities for MPA are apparently no more of a safety risk than MPA.