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The effect of pH on release of PGE 2 from vaginal and endocervical preparations for induction of labour: an in‐vitro study
Author(s) -
JOHNSON T. A.,
GREER I. A.,
KELLY R. W.,
CALDER A. A.
Publication year - 1992
Publication title -
bjog: an international journal of obstetrics and gynaecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.157
H-Index - 164
eISSN - 1471-0528
pISSN - 1470-0328
DOI - 10.1111/j.1471-0528.1992.tb14433.x
Subject(s) - triacetin , chemistry , in vitro , chromatography , biochemistry
Objective To study the effect of pH and precoating with obstetric cream on the release of prostaglandin E 2 (PGE 2 ) from commercially available triacetin and starch based gels, lactose based vaginal tables and sustained release hydrogel polymer pessaries in‐vitro. Design A prospective observational study. Methods PGE 2 preparations held in dialysis bags were placed in Ringers lactate buffer and release of PGE 2 into the buffer was measured over 8–12 h by radio‐immunoassay. The hydrogel polymer pessary was also assessed after precoating with obstetric cream. Main outcome measures In‐vitro PGE 2 release at pH 7.4, pH 5.4 and pH 3.4. Results The gel preparations provided rapid and reliable release, while the lactose based vaginal tablet provided much lower release of PGE 2 with sudden and variable release occurring after 5–8 h, an effect which was enhanced at low pH. With the triacetin gel preparation, release of PGE 2 was reduced at lower pH, while the starch based gel appeared to provide optimal release at pH 5.4. The hydrogel polymer pessaries provided linear release in‐vitro and this was reduced at pH 3.4. In addition, precoating the sustained release hydrogel polymer pessaries with obstetric cream virtually abolished release of PGE 2 . Conclusions As the vagina is normally acid, these results suggest that vaginal pH could influence PGE 2 release and this may result in variable clinical responses. In view of this, pH should be taken into account in the development of preparations for clinical use. Furthermore, the use of obstetric cream should be avoided when administering PGE 2 preparations for induction of labour.