Evaluation of Dimethylformamide (DMF) as an Organic Modifier in Hydrophobicity Index (R[m]) Determination

PURPOSE: Ideal behaviour of mixtures of organic modifier and water is reflected by a linear relationship between refractive index and fraction of organic modifier in the mixture. This study was carried out to investigate dimethylformamide (DMF) as an organic modifier in hydrophobicity index (Rm) determination. METHOD: We quantitatively evaluated the problem of partial miscibility of phases associated with the reversed phase thin layer chromatographic (RPTLC) system; using liquid paraffin as stationary phase and acetone/water mixtures as mobile phase. Ideality of behaviour of acetone/water mixtures was investigated by refractive index measurements. R[m] values of compounds were determined using mixtures of acetone and water as mobile phase. RESULTS: DMF/water mixture behaved ideally across the whole concentration range investigated (0-100 percent) while acetone/water mixture deviated from ideal behaviour when the concentration of acetone in the mixture was 80 percent. DMF also gave a better extrapolation of R[m] value from linear regression of partition data than acetone for bezafibrate used as a test-drug molecule. CONCLUSION : DMF is a better organic modifier than acetone in this RPTLC system. These findings could be extended to drug-receptor and drug design studies. The use of dimethylformamide (DMF) in preference to acetone as organic modifier is proposed in this study

Comparative in-vitro studies on the efficacy of ivermectin against gastrointestinal sheep nematode

Purpose: This study was designed to evaluate the relative efficacy of various brands of ivermectin injection available for use in clinical veterinary practice in Nigeria. Method: Ivermectin injections were evaluated by a larval development assay (LDVA), using the larvae of Strongyles (predominantly Haemonchus contortus) of sheep. The effect of standard solutions of the drug from the various brands on the transformation of L1 to L3 and survival of L3 larvae was used to assess bioactivity. The 50% lethal concentration (LC50) was determined from regression line obtained by probit transformation of the biological data. The LC50 values for each of the brands were compared with that of the innovator brand (Ivomec Super) for any significant difference. Results: The LC50 values obtained for the five brands varied widely. It ranges from 1.1±0.17 ng/ml for the innovator brand to 2.3±0.3, 3.0±0.3, 8.0±0.2 and 17.0±0.3 ng/ml for the other four brands. The biological assays performed on each of the five brands were of comparable precision. LC50 for Ivomec super was significantly different from those of the other four brands (Student's t test, p < 0.01). Conclusion: The bioactivities of brands of ivermectin injections available in Nigeria are significantly different. This is a probable reason for the varied treatment response to various brands of ivermectin injection in veterinary practice in Nigeria. This justifies the need for drug regulatory bodies in Nigeria to ensure that ivermectin injections registered for use in Nigeria meets approved standards before the drugs are allowed to be imported into the country