Diclofenac Sodium Lipid Microsphere Injection

Diclofenac sodium (DS), one of the 3rd generation non-steroidal anti-inflammation drugs (NSAIDs), is of potential analgesic and anti-pyretic effects. It is usually applied to suppress pain induced by all kinds of surgeries. DS embodies the characteristics of fast on-set and long-lasting potency. It could remarkably reduce the dosage of opiod after surgeries, and thus decrease the adverse reactions caused by the opoid analgesic. Also, DS is of better efficacy but less adverse reactions and less accumulation for multiple doses, as compared with other NSAIDs. Intraveous injection could avoid the high first-pass effects of DS.Moreover, it also could reduce the adverse effects due to orally administration. Some of DS injections are now commercially available in some countries excluding China. However, vascular irritation of the preparations due to DS is a serious problem that could not be neglected. Thus, the pursuing for a better preparation of DS is highlighted. Lipid microsphere injection (LM) is a suitable carrier for NSAIDs for its capability of targeting on inflammatory sites naturally. Furthermore, the drug is loaded in the inner phase of the LM, and thus is kept from contacting the vessels.In this study, the long-chain triglycerides (LCT) and middle-chain triglycerides (MCT) were applied as oil phase of DS LM. Formulation and procedure screenings were undergone by single factor method based on the physical properties, particle size distribution,ζ-potential and entrapment efficacy (EE) of the LM. The component and composition of oil phase was investigated. Meanwhile, the sort and amount of emulsifiers and co-emulsifiers were also studied. The effects on the stability of LM such as methods of drug incorporation and homogenization condition were tested as well. Besides, the influences of pH value of the coarse LM on EE, physical and chemical stablitiy of the DS LM were studied as well. The low pH value benefits the high EE of DS in LM. However, it demolished either the physical or the chemical stability of the DS LM. The optimism formulation was as follows:LCT 4.00%, MCT 16.00%, lethcin 3.00%, Tween-80 0.40%, F-68 0.40%, oleic acid 0.06% and glycol 2.50%. Prior to being homogenized 8 times under 70 MPa, the pH value of the coarse LM was adjusted to 6.5.After being filled into 10 ml-vials with nitrogen protection, the LM was sterilized in water bath at 100℃for 30 min. The final product was a near white emulsion-like liquid with particle size 137.9nm. The absolute value of zeta-potential was above 20 mV. The EE of the DS LM is higher than 85%. After being stored at 4℃for 6 months, there was no evident change in appearance, pH value, particle size and distribution,ζ-potential, content and EE of DS LM, which showed the DS LM was quite stable.A high performance liquid chromatography (HPLC) method for DS LM assay was established. The method had high sensitivity and selectivity. It showed a good linearity between the DS concentration of 1-100μg/ml.It was suitable for the quality control of the LM. The HPLC method was used to assay the LM following the dissolution of LM by the mixture of isopropyl alcohol and methanol.An ultra performance liquid chromatography tandem mass spectrometric (UPLC-MS/MS) method had been developed for determination of DS in rat plasma. The method was novel time-saving with high selectivity and sensitivity. Samples were treated by a one-step liquid liquid extraction. Separation was performed on an ACQUITY UPLCTM BEH C18 column (50 mm×2.1 mm i.d.,1.7μm).The mobile phase was consisted of acetonitrile-0.1% ammonium hydroxide aqueous solution (20:80, v/v) initially in a gradient mode. The detection was carried out by means of electrospray ionization mass spectrometry in negative ion mode with multiple reaction monitoring (MRM). The developed method was validated and successfully applied to the pharmacokinetics study of DS aqueous injection and LM injection. The Cmax, AUC(0-t) and t1/2 for DS LM and DS aqueous injection were 25292.267±2412.358μg/L and 32438.417±3958.481μg/L,22620.676±5579.585μg/L-h and 25471.640±2823.119μg/L·h,3.662±0.606 h and 4.816±1.692 h, respectively.The relative bioavailablity of the DS LM to DS aqueous injection was 98.5%.The two preparations have similar pharmacokinetic profile in rats.