The Ins and Outs of Drug-Releasing Vaginal Rings: A Literature Review of Expulsions and Removals

Introduction
There is considerable interest in vaginal ring technology for sustained/controlled release of pharmaceutical drugs to the human vagina. Seven drug-releasing vaginal ring products have reached market and have many other experimental devices are in preclinical/clinical development. Although most women who have use vaginal rings are satisfied and find them acceptable, involuntary ring expulsions and voluntary ring removals are known to occur and are widely reported in the scientific literature. There have been no previous efforts to review the historical data and understand the contributing factors leading to expulsions.

Areas covered
This article is intended to help researchers, clinicians and product developers understand the pertinent factors and issues around ring expulsions and removals, and to inform new research aimed at optimising the design of new ring products. The review contains four sections: (i) introduction to vaginal ring technology; (ii) a discussion of the anatomical, physiological, device, and user factors potentially affecting ring expulsion; (iii) a literature review around involuntary ring expulsions; (iv) a literature review around voluntary ring removals; and (v) concluding remarks and opinions.

Expert Opinion/Commentary
Further research is needed to better understand the factors contributing to involuntary ring expulsions and removals so that rings can be designed from the outset to minimise rates of expulsion and to reduce removals. Determination of optimum ring dimensions and stiffness for each ring product are likely key factors, alongside better counselling around ring removal and reinsertion.

Keywords: silicone elastomer; ethylene vinyl acetate copolymers; thermoplastic polyurethanes; involuntary ring expulsion; voluntary ring removal; mechanical properties; ring dimensions; parity