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Introduction: More than one-third of women experience abnormal uterine bleeding (AUB) during their lifetime. One of the treatment methods of this disease is hormone therapy. Vaginal rings (VRs) containing progesterone hormones could be a good choice for treatment. In this study, the design and construction of a reservoir ring with the ability to release levonorgestrel hormone has been investigated.
Methods: In this experimental study, to make vaginal rings containing levonorgestrel, biocompatible silicone fibers were used, the two ends of which were connected with special caps. Different amounts of LNG including 0.1, 0.2 and 0.4 weight percent relative to paraffin were loaded into the fibers. These three prototypes were named RSC1, RSC2, and RSC3, respectively. The daily and cumulative release of LNG from these rings was measured by spectrophotometer and compared using SPSS software version 16 and analyzed by one-way ANOVA method.
Results: On the first day, there was a burst release that was different for these three prototypes depending on the drug loading percentage. From the second until thirtieth day for RSC3 and from forth until thirtieth day for RSC1 and RSC2, prolonged release was achieved and average daily release for RSC1, RSC2, and RSC3 were 24.10 ± 8.22, 41.77 ± 9.02 and 83.29 ± 5.07µg, respectively.
Conclusion: According to the findings, it is possible to design VRs capable of prolonged and sustained release of LNG for up to 30 days and control their daily release rate based on initial drug loading. This method may be a suitable alternative to oral hormonal pills in the treatment of AUB. 

Introduction: Among 3 to 30 percent of women of reproductive age, experience abnormal uterine bleeding (AUB). Vaginal rings are one of the systems of interest for the local delivery of hormones that due to their polymeric structure allow prolonged release of drug. In this study, the design and fabrication of matrix vaginal rings containing levonorgestrel (LNG) were investigated.
Methods: In this experimental study, at first, two pieces of aluminum mold were designed, then base (A) and cross-linker parts (B) of polymer with LNG were mixed and 48 polymeric rings containing LNG were manufactured by injection molding method. To achieve the desired drug release values in a given time, the effect of temperature, rpm, release environment, different initial loading, cross-linker percentage and a mathematical model to predict release and swelling test were investigated.
Results:  As a result of the experiments, it was revealed that with increasing drug loading, the release rate rises, while increasing the cross-linker percentage reduced the drug release. Finally, the ring A:B=100:9.5 with an initial loading of 0.2 % LNG relative to silicon was selected as an appropriate ring, and release experiments were performed at 37 °C, shaker speed of 80 rpm, and release medium containing 10 % ethanol. Drug release values were measured by spectrophotometer and analyzed by SPSS statistical software version 16.
Conclusion: Based on the results, it can be deduced that matrix vaginal ring containing LNG is a suitable drug delivery system for prolonged release of LNG for treatment of AUB that depending on the drug initial loading and cross-linker percentage, the required diffusion coefficient, and release rate can be achieved in a certain time.