Contraception by Ushercell™ (cellulose sulfate) in formulation:: duration of effect and dose effectiveness

This study evaluated contraception by formulated Ushercell(TM), a uniquely high-molecular-weight form of cellulose sulfate, in the rabbit. Variables included (1) dose effectiveness, (2) duration of effectiveness, and (3) formulation excipients. Vaginally applied carboxymethylcellulose-based Ushercell(TM) gel is contraceptive. A 6% gel is active for at least 18 h; partial activity is observed for at least 24 h. With an application-insemination interval of 0.5 h, Ushercell(TM) as low as 0.1% is contraceptive. Contraception is incomplete with 2% Ushercell(TM) and an application-insemination interval of 24 h. Ushercell(TM) formulations containing a relatively high concentration of Carbopol are ineffective contraceptives, whether the gel is applied before insemination or is premixed with spermatozoa before insemination. Contraceptive activity is restored in Ushercell(TM) formulations with lower Carbopol content. This study shows that formulated Ushercell(TM) is an effective, long-lasting contraceptive and, hence, is bioavailable when vaginally applied. Activity is dependent on the type and relative concentration of formulation excipients. These data support a projected successful outcome of further clinical trials. (C) 2004 Elsevier Inc. All rights reserved.