FACULTY OF PHARMACY
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Item Heavy Metal Contamination of Paediatric Paracetamol and Ascorbic Acid Drug Products in South-West Nigeria.(West African Postgraduate College of Pharmacists (WAPCP), 2019) Thomas, O. E.; Itopa, M. O.; Adegoke, O. A.Background: Water is a primary contributor to human populations’ heavy metals exposure and industrial contamination of products. Consequently, paediatric medications because of their high-water constitution can contribute significantly to intake of heavy metals in excess of allowable limits. There is therefore a need for effective preventive and control strategies. Unfortunately, studies investigating heavy metal content in paediatric formulations in Nigeria are scarce and often limited in the range of elements assayed. Objective: To evaluate elemental impurities in the two most frequently administered paediatric medications-paracetamol and ascorbic acid marketed in South-west Nigeria. Methods: Thirteen paediatric syrup brands were used for the study. Sample pretreatment involved dry ashing followed by digestion using concentrated aqua regia (nitric acid:hydrochloric acid, 3:1). Chromium, lead, copper, cadmium, zinc, nickel, cobalt and manganese were assayed with the atomic absorption spectrophotometer with the limit of detection set at 0.001. Results: The most abundant metal ions present in all the formulations were chromium (1.16-1290.2 mg/) and nickel (2.37-1289.0 mg/L). Cadmium was detected at low concentration in only two of the brands while lead was detected in three brands at concentrations ranging from 0.09 - 0.12 mg/L. The calculated expected daily exposures of lead in the three brands were in excess of the permissible daily exposure for oral drug products. Conclusion: Some of the paracetamol and vitamin C syrups sold in the South-West of Nigeria are contaminated with cadmium, nickel and lead.Item Two New Spectrophotometric Methods for the Determination of Isoniazid in Bulk Form and Tablet Dosage Form.(Istanbul Medipol University, Faculty of Pharmacy, 2019) Adegoke, O. A.; Thomas, O. E.; Babatunde, D. I.; Oyelami, O.; Adediran, A.; Omotosho, A.To develop two new spectrophotometric methods for the analysis of isoniazid in bulk form and tablets. The methods involved condensation of isoniazid with salicylaldehyde and diazo coupling with diazotized p-nitroaniline. Critical factors were optimised; evidence for new product formation, selection of analytical wavelengths, temperature and time and solvent for dilution. Validation was carried out according to ICH guidelines. The new methods were used for isoniazid tablets. Isoniazid formed an imine and azo adduct readily with the two reagents at 30 ⁰C after 5 and 20 mins, and determined at 405 and 420 nm, respectively. Low LODs were obtained for the two methods and recoveries were generally above 98%. The methods were successfully adopted for the assay of isoniazid in tablets and there were no significant differences in the contents when compared with the official titrimetric method of analysis. The methods could find application as in-process method in pharmaceutical industries.Item A New Method for the Microdetermination of Para Aminophenol in Generic Brands of Paracetamol Tablets(Taylor & Francis Group,, 2019) Adegoke, O. A.; Thomas, O. E.; Amao, S. A.; Agboola, S. O.; Omotosho, A. E.In Nigeria, paracetamol is readily available in several retail outlets where the conditions of storage can be poor leading to elevated levels of para-aminophenol (PAP), which is known to be nephrotoxic and hepatotoxic. However, the routine analysis of PAP is mostly by chromatographic separation which requires expensive instrumentation not often available in developing countries. The objective of this research was to develop a sensitive colorimetric method for the quantification of PAP in paracetamol. The method was based on the diazo coupling reaction between diazotised PAP and chromotropic acid. Various reaction parameters critical for optimal detector response were optimized. The validation of the new method was done following the determination of parameters including repeatability, reproducibility and selectivity using current ICH guidelines. The new method was also applied to the assay of PAP in 14 paracetamol tablet samples. The calibration was linear between 0.0297 and 0.2229 mg/mL at 470nm with limits of detection and quantification of 0.0061 and 0.0185 mg/mL, respectively. The recovery was in the range of 95.96 and 102.21 while intra- and inter-day precisions at three different concentrations did not exceed 4.03%. The new method was successfully applied to quantify PAP in paracetamol with percent content varying from 0.14 to 0.21%w/w. A simple and reliable method for the quantification of PAP has been developed and successfully employed to report, for the first time, the presence of the degradation product at levels beyond the allowable limits in paracetamol dosage forms in Nigeria.Item Preferential Solvation of Mordant Black and Solochrome Dark Blue in Mixed Solvents Systems.(Sami Publishing Company, 2019) Thomas, O. E.; Adegoke, O .A.; Kazeem, A. F.; Ezeuchenne, I. C.In this study, the preferential solvation of Mordant Black and Solochrome Dark Blue were investigated in mixed solvent systems of aqueous methanol, ethanol, propan-1-ol, propan-2-ol, methanol: ethanol, ethanol:propan-1-ol, methanol:propan-2-ol, ethanol:propan-1-ol, ethanol:propan-2-ol, propan-1-ol:propan-2-ol and carbon tetrachloride: dimethylformamide. Results showed a deviation of solvation data from ideality over the majority of composition ranges in all the solvent mixtures. The type and contribution of specific and non-specific solute-solvent interactions were analyzed in the framework of the linear solvation energy relationships. Statistical analysis of single, dual, and multiparametric equations revealed that in pure solvents, spectral behaviours of MB and SDB were affected by the polarity and basicity of the solvent milieu respectively. However in aqueous alcohols, polarity of the solvent milieu was the most significant determinant of spectral patterns with α and β parameters playing secondary contributory roles in the spectral changes of MB and SDB, respectively. Multiparametric equations generally yielded the best fitted model in mixed alcohol systems with polarity remaining the largest contributor, followed by β and α of the solvent milieu in that order. Spectral-structure relationships identified ion-dipole interactions involving the charged sulphonate and hydrazone moieties as well as protondonor-acceptor interactions of the common labile hydroxyl groups as mechanisms for the observed solvation data.Item Preferential Solvation of 4-Carboxyl-2,6-dinitrophenylazohydroxynaphthalenes in Aqueous Dimethylformamide and Dimethylsulfoxide Binary Mixtures by UV-Visible Spectroscopy.(Springer New York / Springer Science+Business Media., 2019) Thomas, O. E.; Adegoke, O. A.; Adenmosun, F. G.; Abiodun, O. J.The objective of this study was to evaluate the influence of partly aqueous solvent mixtures on the solubility and azohydrazone equilibrium processes for a group of phenylazohydroxynaphthalenes, AZ-01, AZ-02, AZ-03, and AZ-04, whose applications as potential color additives and chemosensors have been demonstrated in previous studies. The UV-visible spectrum was acquired between 190-900 nm at concentrations of the dyes that precluded molecular aggregation for each dye in aqueous dimethylformamide and dimethylsulfoxide binary mixtures of varying compositions. The plots of E12 against mole fractions of the co-solvent showed deviation from ideality in the behaviors of the four dyes in the aqueous solvent mixtures. The solvation data were largely influenced by the structural chemistry of the dyes. In particular, AZ-01, which contains a free parahydroxyl group that can donate hydrogen to hydrogen bond acceptor solvents showed substantial bathochromic shifts in the aqueous DMF and DMSO mixtures as well as a local accumulation of the organic solvent in its solvation sphere. Conversely, the positional isomer AZ-02 with its ortho hydroxyl group being involved in intramolecular hydrazone rearrangement exhibited dielectric enrichment in both aqueous solvent mixtures. In addition, synergism through formation of the water-DMSO and water-DMF complexes was observed with all the dyes in the solvent mixtures with AZ-01 being solvated by the more polar component of the complex while AZ-02 and AZ-04 were solvated by the less polar solvent mixture component. Thus, the preferential solvation of the phenylazohydroxynaphthalene series from AZ-01 to AZ-04 in the partly aqueous DMSO and DMF solvent mixtures has been successfully studied using UV-visible spectroscopy.Item Spectrophotometric and thermodynamic studies of the charge-transfer complexation of Tranexamic Acid with Chloranilic Acid(Nigeria Association of Pharmacists in Academia, 2018) Thomas, O. E.; Adedoyin, O.Background: Tranexamic acid is a synthetic analogue of lysine that is clinically useful as an antifibrinolytic agent. Due to its lack of chromophores and aromaticity, chemical derivatization is necessitated and outcomes are often poor and/or associated with low sensitivity and poor stability. Objective: To develop a colorimetric method for the determination of tranexamic acid (TXA) following the optimization and parameterization of the charge-transfer (CT) complexation of the drug with chloranilic acid (CAA). Method: The method involved the utilization of TXA as n-electron donor and CAA as π-acceptor in methanol to generate a CT complex. Factors contributory to the formation and stabilization of the complex were optimized. The Benesi-Hilderbrand equation was used to estimate the molar absorptivity and formation constant of the CT band before its application to dosage form analysis. Results: The CT band which absorbed maximally at 520 nm was associated with molar absorptivity of 807 Lmol- 1cm-1 and a large formation constant (1.14x104). The calculated physicochemical properties including transition energy (2.303eV), oscillator strength (0.267), transition dipole moment (5.455 Debye), resonance energy (1.159 eV), ionization potential (8.679 eV) and dissociation energy (5.276 eV) as well as the thermodynamic parameters were indicative of a highly stable charge-transfer complex. Under optimal conditions, the assays of the drug were linear over the range 10-100 μg/mL and the method was accurate and reproducible (inter-day relative errors and standard deviations not greater than 2.92% and 3.40% respectively). When applied to dosage forms, there was no statistical difference in the mean recoveries of the new method when compared to reference method. Conclusion: The new method is rapid, accurate and precise. It can serve as alternative to the routine analysis of tranexamic acid in bulk and dosage forms.Item A new spectrophotometric method for the determination of gabapentin usingchromotropic acid(Istanbul Medipol University, 2018) Adegbolagun, O. M.; Thomas, O. E.; Aiyenale, E. O.; Adegoke, O.A.The purpose was to develop a colorimetric method for determining gabapentin. The method was based on the diazo coupling reaction between diazotized gabapentin and chromotropic acid. The method was validated using ICH guidelines before its application to generic brands of gabapentin. Coupling reaction generated an orange azo adduct whose absorbance was linearly correlated with concentration in the range of 1-6 μg/mL at 470 nm. The method was accurate and precise with recovery range of 97.6-103.1%; intra- and inter-day precisions (%RSD) were less than 0.65% and showed no statistical difference when compared with reference method in the analysis of the dosage forms. The 3D optimization of the adduct revealed an E-type configuration around the azo linkage which would contribute to its stability. The new method can serve as a reliable alternative to the official method for the routine analysis of gabapentin in bulk and dosage forms.Item Colorimetric determination of Olanzapine via charge-transfer complexation with Chloranilic Acid.(Elsevier B.V., 2016) Adegoke, O. A.; Thomas, O. E.; Emmanuel, S. N.The charge-transfer complexation (CTC) formed between olanzapine and chloranilic acid have been studied and used as a sensitive colorimetric method for the determination of olanzapine. Evidence for the formation of the CTC between chloranilic acid (CAA) and olanzapine (OLP) was established by spot tests and TLC. Method development was carried out through selection of analytical wavelength, optimization and validation studies. Physicochemical parameters such as energy of transition, transition dipole, oscillator frequency and ionization energies were estimated and related to the stability of the formed CT band. Thermodynamic properties of the CT band at four temperature levels were also estimated and their inter-relationship established. The reaction was completed at room temperature within 10 min with the evidence of formation of purple-coloured solution with CAA that absorbed maximally at 520 nm. Linearity was obtained in the concentration range of 2–40 µg/mL for OLP (r = 0.9977) with a limit of detection of 1.57 µg/mL. Estimates of accuracies and precisions gave error values less than 2% for both intra- and inter-day assessments. The transition energies were of the order of 2.303 eV. The Gibbs energy varied with the temperature and room temperature values favoured formation of stable complexes. The thermodynamic studies revealed small positive entropy for slightly negative enthalpy change. The method was successfully applied to estimate OLP in tablets and the method was found to be of equivalent accuracy with the Indian Pharmacopoeia’s HPLC method (p > 0.05). The method could find application as a rapid and sensitive determination technique for olanzapine.Item Toxicity of food colours and additives - a review.(Academic Journals, 2015) Thomas, O. E.; Adegoke, O. A.Majority of consumer goods are required to be presented with good aesthetics in order to improve acceptability in terms of colours and in some instances taste. When related to food, beverages and drug products, additives are usually added to mask un-inviting colours, obscure offensive odours and increase taste. Food additives therefore include colourants, sweeteners, preservatives and anti-caking agents. Admissible daily intake limits are often recommended for these additives. Being food products, the amount consumed over time may be subject to individual preferences and thus negating the desire to regulate and control the amount consumed cumulatively. There have been several concerns about the safety of food additives and several batteries of tests, and reports are available in literature. This review attempted to give an update on reports that have surfaced in literature over recent past on the use and safety of food colours and other additives. Some safety concerns have been related to three determinations; cytotoxicity, genotoxicity and induction or potential of inducing mutagenicity. In order to accomplish these targeted evaluations, several tests have been prescribed by International conference on harmonization (ICH), organization for economic co-operation and development (OECD) and European food safety authority (EFSA). It is observed that no single test can give a full proof of safety of these food colours and additives, hence minimal tests are recommended to be carried out in order to guarantee safety of these products. Survey of literature, revealed that once some approved additives or colours become a subject of safety concerns, comprehensive evaluations are carried out by researchers and these have often led to the de-classification of some hitherto reported agents as being non-genotoxic or non-carcinogenic. The declassifications of some food colors and additives as human carcinogens are regularly done following the comprehensive evaluation of results of mutagenicity and genotoxicity tests in vitro and some in vivo tests in mammalian tissues and whole animals. However, such declassifications are often done with caution and the implication is that regular and more comprehensive tests must be carried out. In addition, the requirements of testing for chronic exposures to this and other agents must be emphasized to prevent occurrence of subtle yet terrible side effects resulting from consuming sub-toxic doses of the additives over time.Item Development of a new visible spectrophotometric method for the analysis of Ganciclovir in bulk sample and dosage form.(Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Nigeria, 2015) Thomas, O. E.; Adegoke, O. A.Purpose: To develop and validate a simple visible spectrophotometric method for the quantitative determination of ganciclovir in bulk sample and dosage form. Method: The method was based on the diazo coupling reaction between diazotized ganciclovir and acidified p-dimethylaminobenzaldehyde. Various analytical parameters for the azo adduct were established. Validation of the new method was carried out using current ICH guidelines with parameters including linearity, repeatability, reproducibility and selectivity determined. The developed method was thereafter applied to determine ganciclovir in a commonly available brand. Results: Coupling reaction generated a yellow-coloured product in an alcohol medium with optimal wavelength at 404 nm. Linear correlation was obtained at concentrations of 10.3 - 25.7 μg/mL. The method was accurate and precise with recovery in the range of 99.37 - 103.15 % while intra- and inter-day precision (% RSD) at three different concentrations was < 2.7 %. The limits of detection and quantification were 0.23 and 0.70 μg/mL, respectively. When applied to the analysis of the dosage form, there was no statistically significant difference between the new method and the official HPLC method. Conclusion: The method is simple, inexpensive, reproducible and fast, and can be employed as a reliable alternative to the official method for the routine analysis of ganciclovir in bulk and dosage forms.