A Holstein cow-calf model for the transfer of ciprofloxacin through milk after a long-term intravenous infusion.

This study is part of an ongoing effort to develop animal models that provide milk and sufficient infant (offspring) plasma samples to fully describe a drug's pharmacokinetics to quantitate the risk to the nursing infant. Ciprofloxacin was administered to six healthy Holstein cows as a constant rate intravenous infusion (flow rate was weight adjusted) to achieve a steady-state concentration of approximately 300 ng/mL for 7 days. Plasma and milk samples were collected from the cow at regular intervals over the course of the 7 days. The plasma and milk samples were analyzed for ciprofloxacin by high-performance liquid chromatography. The milk was fed to calves, and calf plasma samples were analyzed to study the lactational transfer of ciprofloxacin from dam to nursing neonate. Remarkably, concentrations of ciprofloxacin in milk were 45 times higher than plasma drug concentrations in the dam. Approximately 6% of the administered dose was transferred to the milk, resulting in an average oral dose of 0.5 mg/kg to the calves with every feeding. The drug did not accumulate in the calves, and plasma concentrations were between one-tenth and one-fifth the plasma concentrations of the dam.

The reaction of N-nitrosamines with pyridinium salts.

N-Nitrosamines react readily with pyridinium salts containing an activated methylene group to give hydrazones. This reaction may serve as the basis for the routine determination of N-nitrosamines.

New derivatives of N-nitrosamines.

Two new derivatives are proposed for determination of nitrosamines by GLC. One is formed by reaction with di(2-chloroethyl) phosphochloridate and the other by reaction with m-trifluorotoluene sulphonyl chloride.

Detection and estimation of antimalarial drugs in body fluids--I. Field test for amodiaquine in urine and saliva.

Simple and specific tests for the detection of antimalarial drugs are required during clinical studies on the sensitivity of Plasmodium falciparum to these drugs. A specific colour test has been developed for amodiaquine which is sensitive enough to permit the visual detection of the drug, following the oral administration of a single 600 mg dose, for up to 10 days in saliva and up to seven weeks in urine. The test is based on the oxidation of amodiaquine to a yellow-coloured derivative using an aqueous solution of potassium persulphate and disodium hydrogen orthophosphate as oxidant. The colour has also been determined spectrophotometrically at 560 nm to achieve a lower detection limit of 0.5 microg amodiaquine in 10 ml biological fluid.

Comparative pharmacokinetics of enrofloxacin and ciprofloxacin in lactating dairy cows and beef steers following intravenous administration of enrofloxacin.

The comparative pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin were investigated in lactating cows and beef steers. The plasma elimination half-life of either enrofloxacin or ciprofloxacin was shorter in cows than in steers. The overall production of ciprofloxacin was slightly higher in steers than in cows (metabolite ratio: 64% and 59%, respectively). There was no significant difference in plasma protein binding of enrofloxacin between cows (percent bound: 59.4%) and steers (percent bound: 60.8%). Ciprofloxacin was more extensively bound to plasma proteins in steers (percent bound: 49.6%) than in cows (percent bound: 33.8%). The steady state volume of distribution of enrofloxacin is comparable in cows (1.55 L/kg) and steers (1.59 L/kg). Within either bovine class, plasma elimination half-life of enrofloxacin and ciprofloxacin are comparable, while plasma protein binding was higher for enrofloxacin than for ciprofloxacin. Ciprofloxacin was more concentrated in milk than enrofloxacin.

Failure to detect amodiaquine in the blood after oral administration.

Plasma and red blood cell concentrations of amodiaquine (AM) and its metabolite, desethylamodiaquine (DAM), were monitored at intervals up to 21 days after a single oral dose of 600 mg amodiaquine in five normal African subjects. Concentrations of AM and DAM were determined using a high performance liquid chromatography technique with a lower limit of sensitivity of 10 ng ml-1 for both compounds. AM was not detectable in plasma and red blood cell samples withdrawn from any of the subjects. DAM was detectable in both media. It appeared in the blood 0.5-1 h after administering AM, reached a peak in 1.5-2 h and subsequently declined slowly. We conclude that AM is rapidly converted to DAM and its blood concentration, compared with that of DAM, is very low if not negligible.

Determination of artelinic acid in blood plasma by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method is described for the analysis of the new antimalarial drug artelinic acid in blood plasma. The influence of mobile phase composition, pH and type of mobile phase modifier on the retention of artelinic acid on the reversed-phase column is reported. Linear calibration curves were obtained in the range 0-500 ng/ml artelinic acid. Intra-assay and inter-assay variability in the analysis of plasma samples spiked with the drug were less than or equal to 15%. Plasma samples of the drug were found to be unstable when stored at -20 degrees C, the concentration of the drug decreasing by over 50% within three days. Plasma samples stored at -70 degrees C remained stable for at least two weeks. Initial pharmacokinetic studies in the rat showed that following intravenous administration, plasma concentrations of artelinic acid declined mono-exponentially. The relatively short elimination half-life (17 +/- 5 min) of artelinic acid is consistent with what is known for qinghaosu and its derivatives.

Side-chain hydroxylation in the metabolism of 8-aminoquinoline antiparasitic agents.

Primaquine, 8-(4-amino-1-methylbutylamino)-6-methoxyquinoline, is an antimalarial 8-aminoquinoline derivative. Although it has been in use since 1952, its metabolism has not been clearly defined. This is due to the instability of the expected aminophenol metabolites and their amphoteric nature, which makes their isolation difficult. Recent studies on the metabolism of WR 238605, a new primaquine analog, has shown that these problems may be solved by extracting the metabolites in the presence of ethyl chloroformate. Subsequent identification of the ethoxycarbonyl derivatives of the metabolites has made it possible to define the in vitro metabolism of primaquine. The primary metabolic pathways of primaquine involved hydroxylation of the phenyl ring of the quinoline nucleus and C-hydroxylation of the 3'-position of the 8-aminoalkylamino side chain. Ring-hydroxylation of primaquine gives rise to 5-hydroxyprimaquine, which on demethylation produces 5-hydroxy-6-demethylprimaquine. Side-chain hydroxylation of primaquine gives rise to 3'-hydroxyprimaquine, which also undergoes O-demethylation to 3'-hydroxy-6-demethylprimaquine. 6-Demethylprimaquine, a putative metabolite of primaquine, also underwent metabolism involving 3'-hydroxylation of the side chain. WR 6026, 8-(6-diethylaminohexylamino)-6-methoxy-4-methylquinoline, is an antileishmanial 8-aminoquinoline derivative. The in vitro metabolism of WR 6026 also results in the formation of side chain-oxygenated metabolites. The present results, together with previous observations on the metabolism of WR 238605 and closely related primaquine analog, suggest that side-chain oxygenation is an important metabolic pathway of antiparasitic 8-aminoquinoline compounds in general.

A high pressure liquid chromatographic procedure for monitoring 1-(2-chloroethyl)-3-(4-trans-methylcyclohexyl)-1-nitrosourea levels in body fluids.

A reverse phase high pressure liquid chromatographic method has been developed for the analysis of 1-(2-chloroethyl)-3-(4-trans-methylcyclohexyl)-1-nitrosourea (methyl-CCNU) levels present in body fluids. A value obtained for the plasma half-life for a single patient indicates that this may be larger than hitherto expected.

The fate of aflatoxins during the production of "Ogiri", a West African fermented melon seed condiment from artificially contaminated seeds.

Twenty-six market samples and four laboratory-prepared samples of "ogiri" were screened for aflatoxin contamination. Aflatoxins were not detected in any of the samples. The fermented product (ogiri) was prepared with Aspergillus flavus-contaminated melon seeds. Losses of 64.7% aflatoxin B1 and 82.9% aflatoxin G1 were observed at the end of the third day of fermentation of the ground melon seeds. The samples were completely detoxified at the fourth day of fermentation. Increase in pH of the mash from 6.2 to 7.2 was observed during fermentation.

Reduction of aflatoxin content of infected cowpea seeds during processing into food.

Cowpeas have been a major source of protein, especially in developing nations. Despite of the fact that aflatoxin contaminations have been found to be mainly common in substrates such as carbohydrates, detection of the toxins in raw cowpeas has also been reported [7]. It is therefore important and necessary to investigate fate of the aflatoxin when raw cowpeas are processed into various products. In Nigeria, cowpea seeds are usually consumed after boiling to softness and mixed with ingredients such as pepper, salt and palm-oil to form a porridge. Other processing methods involve wet milling the cowpea seeds and either steaming in aluminium cups or in leaves to form 'moinmoin', or frying in oil to form 'akara' balls. In this work therefore, the fate of the aflatoxins as a result of the processing of artificially contaminated cowpeas was investigated.

Determination of arteether in blood plasma by high-performance liquid chromatography with ultraviolet detection after hydrolysis acid.

A reversed-phase high-performance liquid chromatographic method is described for determination of the antimalarial agent arteether in blood plasma based on its decomposition in acidic medium and measurement of the major decomposition product, which has been identified as an alpha,beta-unsaturated decalone. Linear calibration curves were obtained in the range 0-250 ng/ml arteether and the recovery of the drug from plasma was found to be quantitative. There is no interference from desoxyarteether, the putative major metabolite of arteether. The method has been applied to the measurement of arteether in the plasma of rats given 110 mg/kg by intramuscular injection of the drug as a solution in sunflower oil.

Biomimetic metabolism of artelinic acid by chemical cytochrome P-450 model systems.

PURPOSE: To study the reaction of artelinic acid with chemical model systems of cytochrome P-450 as a means of obtaining authentic samples of the putative metabolites necessary for identification of the mammalian metabolites of artelinic acid. METHODS: Artelinic acid was reacted with different organic complexes of iron(II). The reaction products were isolated and characterized by NMR and thermospray mass spectroscopy. RESULTS: Five compounds which are putative metabolites of artelinic acid were isolated from these reactions and unambiguously identified, while the identity of two other compounds await final confirmation. CONCLUSIONS: Standards of possible metabolites of artelinic acid can be produced by the reaction of the compound with ferrous complexes that may simulate cytochrome P-450 catalyzed metabolism of xenobiotics. This approach may provide a simple and versatile method for the formation of metabolites of artemisinin compounds which is more advantageous than previous approaches with fungal-based systems.

Metabolism of a candidate 8-aminoquinoline antimalarial agent, WR 238605, by rat liver microsomes.

The in vitro metabolism of the 8-aminoquinoline, 8-(4-amino-1- methylbutylamino-2,6-dimethoxy-4-methyl-5-(3-trifluromethyl- phenoxy)quinoline (WR 238605), by rat liver microsomes was studied. After incubation of WR 238605 with rat liver microsomes, the metabolites were isolated either by direct solvent extraction or by extraction in the presence of ethyl chloroformate. WR 238605 was extensively metabolized to aminophenolic compounds, which underwent air oxidation during the isolation process to a mixture of quinones and quinoneimines. Because of the instability of the metabolites toward air oxidation, most of them could only be isolated as the ethoxycarbonyl derivatives by in situ derivatization with ethyl chloroformate. The metabolism of WR 238605 involved the expected metabolic pathways, such as O-demethylation, N-dealkylation, N-oxidation, and oxidative deamination. In addition, C-hydroxylation involving the 8-aminoalkylamino side chain, which was previously unknown for 8-aminoquinoline analogs, was found to be an important metabolic pathway for WR 238605. Most of the metabolites retained the 5-(m-trifluoromethyl)phenoxy group of WR 238605. Direct and indirect supporting evidence for the structure of the metabolites of WR 238605 came from the concomitant study of the in vitro metabolism of six other compounds that are putative metabolites of WR 238605.