The physicochemical and antibacterial properties of ciprofloxacin-Mg2+ complex.

PURPOSE: Co-administration of quinolone antibiotics with cation-containing medicaments such as, antacids has been reported to influence the overall bioavailability leading to subtherapeutic plasma concentrations of these antibiotics in humans. OBJECTIVES OF THE STUDY: The present work was designed to evaluate the binding constant, binding molar ratio, influence of temperature on the binding constant of ciprofloxacin-Mg2+ and to determine the antimicrobial activity of ciprofloxacin and ciprofloxacin-Mg2+. METHODS: Job's method of continuous variation and Bonesi-Hildebrand equation were adopted to determine the molar ratio and stability constant respectively. The antibacterial activity was determined by the Agar diffusion method. RESULTS: A complexation molar ratio of 1:1 was obtained for ciprofloxacin-Mg2+ complex. The stability constants were 3.59 and 3.50 at 25 degrees C and 60 degrees C respectively. There was a significant difference between the zones of inhibition of ciprofloxacin-Mg2+ complex and that of ciprofloxacin alone against E. coli, P. aeruginosa, and S. aureus (p < 0.05). This difference showed that the complex formed was not as active as ciprofloxacin. CONCLUSION: The present studies have shown that ciprofloxacin readily complex with Mg2+ and that the stability constant was temperature dependent. The antibacterial activity of ciprofloxacin was markedly reduced in the presence of Mg2+. Concomitant administration of ciprofloxacin with Mg2. containing medicaments should be avoided to prevent resistance.

In-Vitro Adsorption of Fluoroquinolones on Some Pharmaceutical Adsorbents

PURPOSE: Drug overdose and poisoning are common clinical problems and could occur with the fluoroquinolones -a new series of synthetic antimicrobial agents. It therefore becomes important to study the adsorption of the fluoroquinolones on pharmaceutical adsorbents which could serve as possible antidotes for the emergency treatment of fluoroquinolone overdose or poisoning when they occur. METHOD: The rate and extent of adsorption of the fluoroquinolones on some pharmaceutical adsorbents; namely activated charcoal; kaolin and bentonite were investigated spectrophotometrically RESULTS: The fluoroquinolones adsorbed on activated charcoal rapidly and attained equilibrium within fifteen minutes. The fluoroquinolones however adsorbed on kaolin and bentonite less rapidly and attained equilibrium within two hours. Activated charcoal and bentonite had high adsorption capacities for the fluoroquinolones while kaolin had low adsorption capacities for them. CONCLUSION: Because of the rapid rate of adsorption and high binding capacities exhibited by activated charcoal for the fluoroquinolones; it could be an effective antidote for the fluoroquinolones in cases of overdose or poisoning. Activated charcoal has shown a superior behaviour to both bentonite and kaolin in the adsorption of the fluoroquinolones

An Alternative Colorimetric Method for the Determination of Chloramphenicol

PURPOSE : To develop a simple; cheap; fast; accurate; sensitive and precise colorimetric method that can be used for the determination of chloramphenicol. METHOD : Chloramphenicol was reduced in a mixture of glacial acetic acid and water using titanium (III) chloride at room temperature within 10 min. The reduced product was then heated for 20 min with p-dimethylaminobenzaldehyde to yield the final product whose absorbance was used for the determination of the concentration of chloramphenicol. Results obtained with this method were compared with those obtained with the microbiological assay of chloramphenicol. RESULT : The final product of the two step reaction was greenish - yellow in colour;; absorbed strongly in the visible region and obeyed Beer's law at ?[max]= 440 nm. The method developed was sensitive and accurately determined chloramphenicol in the presence of common excipients and in different dosage forms. There was statistically no significant difference (p less than 0.05) between the results with the method developed and those obtained with the microbiological assay of chloramphenicol. CONCLUSION: A simple; fast; cheap; precise; sensitive and accurate colorimetric method has been developed that could be routinely used for the determination of chloramphenicol in bulk drug and in different dosage forms. The advantage of the method is its speed and simplicity

Kinetics of absorption and elimination of ofloxacin in humans after oral and rectal administrations.

Ofloxacin pharmacokinetics have been studied in four healthy subjects after a single oral or rectal dose, each of 200 mg. For the oral dose tmax was about 2 h, Cmax 1.96 +/- 0.56 micrograms/ml and AUC1-15 15.22 micrograms/ml.h. Two-phase elimination pharmacol kinetics were observed for the oral dose, t1/2 for the rapid elimination phase was 3.3 h and for the slow phase 10 h. With the rectal dose tmax was 6 h, Cmax 0.71 +/- 0.44 microgram/ml and AUC0-15 7.58 micrograms/ml.h. The relative rectal bioavailability (AUC rectal/AUC oral) was 49.8%. Elimination rate of the rectal dose was generally slow (t1/2 = 9 h), an observation attributable to the sustained-release effect of the rectal suppository base, PEG 6000. The indication is that the rectal formulation cannot be substituted totally for the oral without first increasing the rectal dose; the 200 mg suppository can however be employed as a follow-up therapy to the oral dose in certain situations.

Colorimetric determination of the fluoroquinolones.

Ciprofloxacin, ofloxacin and norfloxacin formed an amber coloured complex with iron(III) nitrate nonahydrate. The complex, which formed instantaneously at room temperature, was stable. The solutions of the complex obeyed Beer's law at 370 nm, the wavelength of maximum absorption of radiation (lambda[max]). The A(1%) for norfloxacin, ofloxacin and ciprofloxacin was 202, 207 and 235 respectively. The formation of the complex was the basis for the quantitative and qualitative determination of the drugs. There was statistically no significant difference (P < 0.05) between the results obtained quantitatively by this colorimetric method and those obtained by the microbiological assay method.

Kinetics and mechanism of hydroxy compound cinnamoylation in acetonitrile catalyzed by N-methylimidazole and 4-dimethylaminopyridine.

The kinetics of reaction of the acylating agents trans-cinnamic anhydride and trans-cinnamoyl chloride with the hydroxy compounds n-propyl alcohol and water in the presence of N-methylimidazole and 4-dimethylaminopyridine were studied spectrophotometrically in acetonitrile solution at 25 degrees. The acid chloride reacted via the intermediate formation of the N-acyl catalyst, which underwent general base-catalyzed reaction with the hydroxy compound. The anhydride did not form the N-acyl intermediate, but instead underwent direct general base catalysis. In the presence of water, all systems formed the N-acyl intermediate. The mechanistic route followed by the system was determined by the nucleophilicity of the catalyst, the ability of the leaving group, and the polarity of the solvent.

Solvent effects on the cinnamoylation of n-propyl alcohol catalyzed by N-methylimidazole and 4-dimethylaminopyridine.

The kinetics of reaction of trans-cinnamic anhydride or trans-cinnamoyl chloride with n-propyl alcohol, catalyzed by N-methylimidazole or 4-dimethylaminopyridine, were studied spectrophotometrically at 25 degrees in methyl ethyl ketone, ethylene dichloride, methylene chloride, and toluene. The acid chloride reacted in all solvents via the intermediate formation of the N-acyl catalyst, which underwent reaction with the alcohol catalyzed by another molecule of the base. The anhydride did not form the intermediate in any of the solvents, but underwent direct general base catalysis. The rate of the anhydride reactions was not sensitive to solvent polarity, whereas the rate of the chloride reactions tended to increase as the solvent polarity decreased. A kinetic analysis is given of the effect of ion-pair formation on the kinetics of acyl transfer in systems where the charged N-acyl catalyst intermediate is formed.