Objective: The drug use-results survey of Metronidazole gel (Rozex® gel 0.75%: hereinafter, this is called “this medicine”) was conducted for the purpose of assessing the safety and effectiveness of this medicine in clinical practice including long-term use. Methods: Patients who initiated treatment with this medicine for sterilization and reduction of odor at cancerous skin ulcer for the first time were registered by the central registration method. The longest period of observation was 1 year. Results: The safety analysis set included 301 patients. The incidence proportion of adverse drug reaction was 3.32% (in 10 of 301 patients), with no serious events. The overall improvement rate was 73.7% (in 205 of 278 patients). At the final observation, the improvement rate of odor by physician's assessment was 80.2% (in 203 of 253 patients) and the improvement rate of patient's satisfaction was 70.1% (in 82 of 117 patients), respectively. Conclusion: The present study demonstrated that this medicine is safe and effective for sterilization and reduction of odor at cancerous skin ulcer, and leads to high treatment satisfaction of patients.

In Japan, a re-examination system was introduced in the 1970s, and Post-marketing surveillance (PMS) has been conducted in many cases after the launch of new drugs or the approval of new indications for existing drugs. The revised Good Post-marketing Study Practice (r-GPSP) was enacted in 1 April 2018, and more scientific approach has been required for PMS. The survey aims to identify what kinds of change occurred in the PMS planned after r-GPSP enacted. As for the study method, after confirming the review report of each product, Risk Management Plan (RMP), and the package insert, and extracting necessary items, tabulation and analysis were performed. As a result of analysis, Drug Use Investigations (DUI) still accounted for more than 60％ of the total in PMS. Regarding the target number of DUI, Fifty-eight out of 90 had a sample size of 500 or fewer, only 3 studies exceeded 3,000. Regarding the newly introduced Post-marketing database surveillance (DB study) after r-GPSP enacted, 13 products and 18 surveillances were confirmed, although the number was not as large as the number of DUI. The most used database was Medical Data Vision Co., Ltd. (MDV), which were used in twelve DB studies, and cardiovascular disease and interstitial pneumonia were set as survey targets for safety considerations in multiple studies. There was no Drug Use Comparative Investigation. Furthermore, there were two products which were approved on the condition with re-examination period but did not required additional Pharmacovigilance activities. In terms of sample size calculation, 88 out of 135 studies mentioned rationales for setting the number of samples. Of which, 58 studies had statistical rationales. In many studies, the sample size calculation method that was commonly used in conventional PMSs, called ‘Rule of three’ was described as the statistical rational. After r-GPSP enacted, newly introduced Post-marketing surveillance, including DB surveys, and the scientific approach recommended by PMDA have been adopted in companies gradually. In the future, in order to further promote the scientific approach, it is necessary to further improve the capability of human resources of companies involved in PMS.