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N PROFGUANTAIA. "SE OF ELISA METHOD TO DETERMINE CHLORAMPHENICOL KINETICS IN RED MASAAI SHEEP AFTER INTRAMUSCULAR INJECTION.". In: j. VET PHARMACO. THERAP. O Wesongah*l, GA Murilla, AN Guantai, RE Mdachi I, WM Karanja and TE Maitho; 2007. Abstract

hloramphenicol is a broad-spectrum antibiotic widely used in human and veterinary medicine due to its low cost and ready availability. However its use has been associated with serious adverse effects, (bone marrow suppression, hemolytic anaemia and aplastic anaemia) that may or may not be dose related. Consequently chloramphenicol is currently banned for use in food producing animals and restricted to non-food producing animals and management of life threatening infections in humans in absence of alternative therapy. Exposure to chloramphenicol can occur after regular consumption of animal foods from treated animals. Therefore the pharmacokinetic of chloramphenicol should be determined using a highly sensitive and specific assay method that can detect residue levels at the lowest concentration possible. Previous methods were limited due to low sensitivity (10 ng/m1-50Ong/mi). Therefore the aim of this study was to determine pharmacokinetics of chloramphenicol and potential residue levels in food producing animals using a published highly sensitive detection method; Chloramphenicol enzyme-linked immunosorbent assay, with a detection limit of 0.1 ng/ml. Methods: Eight male red Maasai sheep aged 9 to 12 months and weighing between 21kg to 25 kg, were weaned and allowed to acclimatize for three weeks. Pre-treatment blood samples (10m1) was collected from each animal and then 25mg/kg chloramphenicol sodium succinate administered by deep intramuscular injection. Post treatment blood samples were collected at 5, 10, 15 and 30minutes, I, 2, 4, 6 8, 12, 24 and 32 hour intervals then twice a day (week 1), once daily (week 2) thrice daily (week 3) twice daily (week 4). Phannacokinetic parameters were measured using chloramphenicol ELISA method. Data was analyzed by fitting four, parameter logistics regression curve of calibration standards and sample chloramphenicol concentration calculated from optical densities using ELISA data Eiaquik program (MC. Eisler, 1995). Samples were analyzed in duplicate. Results from these assays were compared with those from published data with respect to elimination half life, species variation, and minimum retention time. Results: Chlorarnphenicol elimination half life (36.4+3.66 h) obtained in the present study was significantly (P<0.05) longer than that of 5.75+1.25 h reported in similar species using colorimetric method. The method was able to detect the drug 7 days post administration. The area under the curve of 124,487.8 ng.h/m1 observed in sheep in the present study was significant higher than that of 31.220+3.25 rig.himl reported in literature in goats using similar treatment route and dose but different assay method. Conclusion: Chloramphenicol pharmacokinetic parameters are significantly influenced by animal species and analytical assay methods used in their determination and care must be taken when reporting the residue levels in food producing animals.

N PROFGUANTAIA. "SELF MEDICATION IN MANAGEMENT OF MINOR HEALTH PROBLEMS IN KENYA.". In: THE EAST AFRICAN MEDICAL JOURNAL. C.K. Maitai, AN Guantai, Mwangi; 1981. Abstract
A survey of proprietary pharmaceutical products used inslf-medication, in Kenya, has been undertaken. Out of 472 products covered in the survey, 32% were those used for gastrointestinal disorders and 18% for respiratory disorders. The significance and limitations of self-medication as they relate to management of minor health problems are discussed.
Ebeshi BU, Bolaji OO, Oluka MN, Edebi VN, Soyinka JO, Guantai AN. "Simple Reversed-Phase High Performance Liquid Chromatographic Estimation of the Antiretroviral Agent Efavirenz from Human Plasma." British Journal of Pharmaceutical Research. 2014;4(1):145-157. Abstract2014_-_simple_reversed-phase_high_performance.pdf

Aims: Sequel to the resurgence of TB co-infection in HIV/AIDS patients in sub-Saharan Africa, efavirenz has become an important component of the highly active antiretroviral treatment (HAART). The objective of this study therefore is to provide a simple reversedphase high performance liquid chromatographic (HPLC) method for the determination of efavirenz in human plasma.

Study Design: Method development and experimental study.
Place and Duration of Study: School of Pharmacy, University of Nairobi, Nairobi, Kenya, between October 2009 and September 2010.

Methodology: A 500μl drug-free plasma sample was each placed in six different centrifuge tubes (2ml) and varying aliquots of the stock solution (100μg/ml) of efavirenz were spiked and vortexed for 60sec to give concentrations of 0.5, 1.0, 2.0, 4.0, 8.0 and 16μg/ml for calibration standards and 2.0, 4.0, 8.0 and 16.0μg/ml for quality control samples. The off-column sample pretreatment was carried out by protein precipitation
using ice-cold acetonitrile. The samples were chromatographed in a phenomenex (C18) 5μm particle size column with 250x4.6mm I.D and UV detection at 254nm using a mobile phase, which was made up of a mixture of solutions A and B. Both consisted of acetonitrile, 25mM ammonium acetate buffer and glacial acetic acid in proportions of 90:10:0.1 and 10:90:0.1(v/v), respectively. The analytical technique was validated for precision, accuracy and analyte recovery.

Results: The calibration plot for efavirenz was found to be linear over the concentration range of 0.5 to 16.0μg/ml with the regression line equation obtained as y=26842x–409.4 and the regression coefficient (R2=0.999), which allows for accurate reading of the concentrations of the test samples. The RSD (%) in intraday and interday assays ranged from 0.44 to 0.78%. Accuracy ranged from 92 to 110% and the recovery was >97%.

Conclusion: This new HPLC method is simple, reproducible and cost-effective and can be used for therapeutic drug monitoring of efavirenz in HIV/AIDS patients on HAART as demonstrated in this study.

Kamau FN, Kibwage IO, Muriuki G, Guantai, A N, Chepkwony H, Hoogmartens J, Roets E, Busson R. "Steroidal Indoxyls: Evaluation of Pk, values and anti-inflammatory activity.". 2006. Abstract

Three steroidal indoxyls, 3-oxo-16,17-seco-16;.nor-l,4-androstadien-15-(7'-methoxy-2-indoxyliden)17-oic acid, 1-(2'-indoxyliden)-2-nor-l,2-secocholestan-3~ oic acid and 1-(5'- chloro-2-indoxyliden)-2-nor-l,2-secocholestan-3-oic acid were synthesized and screened for anti-inflammatory activity. Their pK. values were also determined using a solubility method. The first compound, 3-oxo-16,17- seco-16-nor-l ,4-androstadien-15-(7' -methoxy-2-indoxyliden) 17 -oic acid, had an EDso value of 15.3 mg/kg and a pK. of 7.09. The cholestane derivative, 1-(2'-indoxyliden)-2-nor-l,2-secocholestan-3-oic acid, and its chloro analogue 1-(5'-chloro-2-indoxyliden)-2-nor-l,2-secocholestan-3-oic acid had EDso values of 16.2 and 22.8 mg/kg, while their pK. values were 6.56 and 7.07, respectively, suggesting that these compounds are relatively weak acids.

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