[Shelf-lives of morphine and pethidine solutions stored in patient-controlled analgesia devices: physico-chemical and microbiological stability study].
Morphine and meperidine in Patient-Controlled Analgesic devices are commonly used to treat chronic pain patients. These devices deliver a programmed amount of drug and allow self-administration by the patient depending on the pain. In our department of pharmacy, 300 devices were manufactured in 2003. The aim of this study was to assess their shelf-life. The devices were filled aseptically and without preservatives with 1 and 40 mg/ml morphine solution and 5 and 20 mg/ml meperidine and stored over 30 days at room temperature and protected from light. Culture assay of the solutions showed that they remained sterile for 30 days. No turbidity of any solutions from samples collected twice a week was noticed. pH and osmolarity remained constant. Drug concentrations were determined using stability indicating HPLC method, as we showed that degradation products can be separated from the drugs. Little loss of meperidine occurred within 21 days (<5%) and morphine concentration, which increased, because of solvent evaporation, remained lower than 5% within 21 days but increased up to 10% after 30 days. No traces of degradation products (pseudomorphine or pethidic acid) were detected. The physicochemical and microbiological stability of morphine and meperidine hydrochlorides stored in such devices has been established for 21 days at room temperature and protected from light.