Objective: Injection diclofenac sodium available at present as a 3-ml formulation is administered intragluteally. Standard needles may not reach the gluteus maximus muscle in many cases, especially in obese patients. Alternative sites like the deltoid have been suggested to be more suitable for these patients. Diclofenac sodium 75 mg/ml was prepared to facilitate intradeltoid administration. The objective of this study was to determine pharmacokinetic parameters and to compare the bioavailability of the new formulation of injection diclofenac sodium (75 mg/ml), given as an intradeltoid injection, with the reference formulation (75 mg/3 ml) given intragluteally.
Research design/methods: A single-dose, two-way bioequivalence study was carried out in 18 healthy, Indian, male volunteers with a washout period of 5 days. Blood samples were collected up to 6 h after drug administration and analyzed using a prevalidated HPLC method.
Results: The mean C(max) and T(max), for the test and reference formulations were 1.95 microg/ml, 1.89 microg/ml and 0.39 h, 0.43 h respectively. AUC values from 0 to last measurable time point 't' observed for test and reference formulations were 3.37 microg.h/ml and 3.28 microg.h/ml respectively. The mean AUC 0 - infinity for test and reference formulations was 3.57 microg.h/ml and 3.52 microg.h/ml.
Conclusion: Results suggest that the test and reference formulations of injection diclofenac sodium 75 mg given intradeltoid and intragluteally are bioequivalent. The test formulation would be especially helpful in the management of obese/overweight patients and patients with thick subcutaneous fat in the gluteal region. It would increase the success rate of intramuscular deposition of the medication.