Determination of dose dependence in repeated dose toxicity studies when mid-dose alone is insignificant.

Repeated dose toxicity studies with rodents are regulatory requirements for registering chemical substances like drugs and pesticides with the government regulatory agencies. Usually 4 groups of animals, including a control group, are used in repeated dose toxicity studies. Williams' test, Dunnett's test and Jonckheere's trend test are generally used to evaluate the data obtained from these studies. Selection of a statistical tool is relatively easy, when the data obtained from the groups of animals show a dose-dependency. But, occasionally a significance difference, compared to control, is not seen in the mid-dose group alone, thus losing the dose-dependency. We attempted to find the appropriate statistical tool for analyzing the quantitative data obtained from repeated dose toxicity studies, when the data of the mid-dose group alone do not show a significant difference, compared to control. The commonly used Williams' test to analyse such data has a disadvantage as it assigns an estimated mean value for the mid-dose group, rather than the original mean value, for the analysis. Hence, it is likely that Williams' test may misjudge in establishing a dose dependency, when in reality it does not exists. Therefore, to analyse such data we suggest the use of Dunnett's multiple comparison test, to compare each dose group with the control, followed by Jonckheere's trend test for examining dose dependency.

Development of gelatin microspheres loaded with diclofenac sodium for intra-articular administration.

We have previously reported on the targeting of diclofenac sodium in joint inflammation using gelatin magnetic microspheres. To overcome complications in the administration of magnetic microspheres and achieve higher targeting efficiency, the present work focuses on the formulation of gelatin microspheres for intra-articular administration. Drug-loaded microspheres were prepared by the emulsification/cross-linking method, characterized by drug loading, size distribution, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), gas chromatography, and in vitro release studies. The targeting efficiency of microspheres was studied in vivo in rabbits. The microspheres showed drug loading of 9.8, 18.3, and 26.7% w/w with an average size range of 37-46 µm, depending upon the drug-polymer ratio. They were spherical in nature and free from surface drug as evidenced by the SEM photographs. FT-IR, DSC, and XRD revealed the absence of drug-polymer interaction and amorphous nature of entrapped drug. Gas chromatography confirms the absences of residual glutaraldehyde. The formulated microspheres could prolong the drug release up to 30 days in vitro. About 81.2 and 43.7% of administered drug in the microspheres were recovered from the target joint after 1 and 7 days of postintra-articular injection, respectively, revealing good targeting efficiency.

Targeted delivery of diclofenac sodium via gelatin magnetic microspheres formulated for intra-arterial administration.

In the present work, we have attempted to deliver diclofenac sodium to a target site by intra-arterial injection of gelatin magnetic microspheres and subsequent localization using an external magnet. Drug-loaded magnetic microspheres were prepared by emulsification/cross-linking method, characterized by drug loading, magnetite content, size distribution, optical microscopy, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) analysis, differential scanning calorimetry (DSC), X-ray diffraction (XRD), absence of glutaraldehyde by gas chromatography, and in vitro release studies. The targeting efficiency and the therapeutic efficacy of microspheres were studied in vivo in rabbits. The microspheres showed drug loading of 9.1, 18.7, 24.9% w/w, magnetite content of 27.8-28.9% w/w with an average size range of 25-30.6 mum, depending upon the drug-polymer ratio. They were spherical in nature as evidenced by optical microscopy and SEM. FT-IR, DSC, and XRD studies revealed the absence of drug-polymer interaction. Gas chromatography confirmed the absence of residual glutaraldehyde. The microspheres were able to prolong the drug release over 24-30 days and the application of sonication during in vitro release study has slightly increased the release rate. After intra-arterial administration of microspheres, 77.7% of injected dose was recovered at the target site which revealed good targeting efficiency. The microspheres effectively reduced joint swelling, but lesser extent than the oral diclofenac sodium in high dose, in antigen induced arthritic rabbits without producing gastric ulceration which was observed in rabbits treated with oral diclofenac sodium.

Targeted delivery of diclofenac sodium via gelatin magnetic microspheres formulated for intra-arterial administration.

In the present work, we have attempted to deliver diclofenac sodium to a target site by intra-arterial injection of gelatin magnetic microspheres and subsequent localization using an external magnet. Drug-loaded magnetic microspheres were prepared by emulsification/cross-linking method, characterized by drug loading, magnetite content, size distribution, optical microscopy, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) analysis, differential scanning calorimetry (DSC), X-ray diffraction (XRD), absence of glutaraldehyde by gas chromatography, and in vitro release studies. The targeting efficiency and the therapeutic efficacy of microspheres were studied in vivo in rabbits. The microspheres showed drug loading of 9.1, 18.7, 24.9 per cent w/w, magnetite content of 27.8-28.9 per cent w/w with an average size range of 25-30.6 mum, depending upon the drug-polymer ratio. They were spherical in nature as evidenced by optical microscopy and SEM. FT-IR, DSC, and XRD studies revealed the absence of drug-polymer interaction. Gas chromatography confirmed the absence of residual glutaraldehyde. The microspheres were able to prolong the drug release over 24-30 days and the application of sonication during in vitro release study has slightly increased the release rate. After intra-arterial administration of microspheres, 77.7 per cent of injected dose was recovered at the target site which revealed good targeting efficiency. The microspheres effectively reduced joint swelling, but lesser extent than the oral diclofenac sodium in high dose, in antigen induced arthritic rabbits without producing gastric ulceration which was observed in rabbits treated with oral diclofenac sodium.

Ultrasonically controlled release and targeted delivery of diclofenac sodium via gelatin magnetic microspheres.

In the present work, an attempt was made to target diclofenac sodium to its site of action through magnetic gelatin microspheres. The gelatin magnetic microspheres loaded with 8.9% w/w of diclofenac sodium and 28.7% w/w of magnetite were formulated by emulsification/cross-linking with glutaraldehyde. The formulated microspheres were characterized by particle size distribution, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction and in vitro release studies. The in vivo distribution and targetability of gelatin magnetic microspheres after i.v. administration were studied in rabbits. The formulated microspheres were below 5 microm and spherical in nature as evidenced by the SEM photographs. DSC and X-ray diffraction studies revealed the absence of drug-polymer interaction. Encapsulated diclofenac sodium was released slowly more than 18 days. Application of sonication, as external stimuli to enhance drug release, during release study, has slightly increased the release rate. The formulated microspheres were injected intravenously after keeping a suitable magnet near the target area. The quantity of drug available at the target and non-target area was determined by HPLC. About 5.5% of injected dose localized near the target organ. Majority of injected dose was recovered from lungs, spleen and liver indicating localization of microspheres in these organs. Further studies are required to improve the targeting efficiency of gelatin microspheres by modifying surface properties to overcome phagocytosis and by selecting suitable particle size to avoid the entrapment of microspheres in non-target organs.