Chemical Stability of Tramadol Hydrochloride Injection Admixed with Selected Pain Drugs

Background: Tramadol hydrochloride (HCl) and ketorolac tromethamine are analgesic drugs, which are commonly used in combination in postoperative pain management. According to some studies, metoclopramide and magnesium sulfate (MgSO₄) as adjuvant agents can improve analgesia and decrease the need for other pain drugs. Materials and Methods: The chemical stability of tramadol HCl combined with ketorolac tromethamine and metoclopramide HCl has been studied using a stability-indicating high-performance liquid chromatographic assay method. Calibration curves were produced using linear regression of the peak area against concentration of each drug, with an r² value ≥ 0.96. Our aim was to investigate the stability of admixture solution of tramadol HCl combined with ketorolac tromethamine and metoclopramide HCl for 48 h (25°C) and 5 days (5°C), with MgSO₄, which has never been assessed. Results: Data obtained for admixtures prepared and stored at temperatures of 25°C and 5°C, show that all drugs have reached at least 98% of the initial concentration. Conclusions: For the purpose of pre-preparing drug admixtures to use with confi dence, tramadol HCl infusions may be prepared in advance and then thawed before use in clinical units. On the basis of our results, the intravenous mixture of tramadol (7.69 mg/mL), metoclopramide (0.19 mg/mL), ketorolac (1.15 mg/mL), and magnesium sulfate (77 mg/mL) may be considered for a possible commercial formulation.