Pharmacokinetics of pentoxifylline in dogs after oral and intravenous administration.

OBJECTIVE: To evaluate the pharmacokinetics of pentoxifylline (PTX) and its 5-hydroxyhexyl-metabolite, metabolite 1 (M1), in dogs after IV administration of a single dose and oral administration of multiple doses. ANIMALS: 7 sexually intact, female, mixed-breed dogs. PROCEDURE: A crossover study design was used so that each of the dogs received all treatments in random order. A drug-free period of 5 days was allowed between treatments. Treatments included IV administration of a single dose of PTX (15 mg/kg of body weight), oral administration of PTX with food at a dosage of 15 mg/kg (q 8 h) for 5 days, and oral administration of PTX without food at a dosage of 15 mg/kg (q 8 h) for 5 days. Blood samples were taken at 0.25, 0.5, 1, 1.5, 2, 2.5, and 3 hours after the first and last dose of PTX was administered PO, and at 5, 10, 20, 40, 80, and 160 minutes after PTX was administered IV. RESULTS: PTX was rapidly absorbed and eliminated after oral administration. Mean bioavailability after oral administration ranged from 15 to 32% among treatment groups and was not affected by the presence of food. Higher plasma PTX concentrations and apparent bioavailability were observed after oral administration of the first dose, compared with the last dose during the 5-day treatment regimens. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, oral administration of 15 mg of PTX/kg results in plasma concentrations similar to those produced by therapeutic doses in humans, and a three-times-a-day dosing regimen is the most appropriate.

Immunochemical detection of hepatic cocaine-protein adducts in mice.

Cocaine is capable of producing hepatic necrosis in laboratory animals and humans. Studies in mice indicate that N-oxidative metabolism of cocaine is required for hepatotoxicity and have suggested that toxicity may result from the adduction of proteins by cocaine-reactive metabolites. To aid in identifying protein targets for cocaine-reactive metabolites, an antibody was raised in rabbits immunized with cocaine linked via the tropane nitrogen to a carrier protein (bovine serum albumin). Hepatic proteins from cocaine-treated mice (ICR males, 50 mg of cocaine/kg of body weight, ip) and saline-treated controls were prepared from whole liver homogenate or following subcellular fractionation, and Western blot analyses of hepatic proteins using this antibody were conducted following one- and two-dimensional SDS-PAGE. Analysis of liver homogenate from cocaine-treated mice revealed major protein targets with approximate molecular masses of 20 kDa (pI = 6.0), 44 kDa (two proteins with pI's of 5.0 and 7.0), 52-54 kDa (pI = 4.5), and 64 kDa (pI = 5.5). These specific protein targets were shown to be localized in the mitochondria and microsomes. Several minor bands of immunoreactivity were also seen in mice treated with cocaine, but not in saline-treated controls. Pretreatment of mice with the P450 inhibitor SKF 525A diminished or eliminated the formation of these cocaine-protein adducts. Liver sections from cocaine-treated mice immunostained using the antibody indicated the presence of cocaine-adducted proteins in the centrilobular and midzonal regions of the lobule, corresponding to areas of hepatocyte swelling and necrosis. This study indicates that reactive metabolites from cocaine bind to discrete proteins in specific regions of the liver, consistent with a role for protein adduction in cocaine hepatotoxicity.

Implementing and assessing organizational practices in local health departments.

One of the most difficult forms of public health practice to characterize involves governmental public health agencies, especially at the local level. A lack of consensus within the public health community as to the purpose and content of organizational public health practice inhibits efforts to increase the capability of public health to address effectively its core functions of assessment, policy development, and assurance. Meaningful capacity building efforts must establish both benchmarks and expectations for the organizational practice of public health. Those markers must be established so that the impact of practice on outcomes and health status can be examined. A model identifying 10 organizational practices was established through the work of the Centers for Disease Control and Prevention (CDC) in collaboration with national practice organizations. Early applications of the model to public health capacity building activities have been effective. Among the applications have been approaches to surveillance of health department practice, certification of local health departments using practice guidelines, and development of leadership within the public health enterprise. Although results are promising, use of the model requires additional external examination and validation, as well as acceptance and consensus within the public health community. The development of organizational practice guidelines for public health agencies may be useful in further efforts to characterize and measure public health practice and its impact on the public's health.

An assay for cocaethylene and other cocaine metabolites in liver using high-performance liquid chromatography.

Cocaethylene (benzoylecgonine ethyl ester or ethyl cocaine) is a transesterification product of cocaine and ethanol that has been observed in the urine of individuals using these drugs in combination. There is evidence that cocaethylene is pharmacologically active, and its formation in vivo may contribute to the toxicity of cocaine. A new method is presented here which enables the quantification of cocaethylene and cocaine, as well as the cocaine metabolites benzoylecgonine and norcocaine in liver tissue. This method utilizes high-performance liquid chromatography with uv detection (235 nm), and the propyl ester of cocaine is used as an internal standard. Liver homogenates are first buffered with 0.1 N dibasic potassium phosphate (pH 9.1) and then extracted with methylene chloride:isopropanol (9:1). Extraction efficiencies were approximately 75-85% for the compounds of interest. The coefficient of variation for replicate determinations (N = 10) of cocaethylene concentration was 5.75%, with comparable values obtained for cocaine, norcocaine, and benzoylecgonine. The detection limit for cocaethylene, based on a peak height threefold greater than background noise, was approximately 1.7 ng of injected compound. Using this method, it was demonstrated that cocaethylene is present in mouse liver following cocaine and ethanol administration, with an apparent rapid rate of formation and elimination.

Analytical techniques in dissolution testing and bioavailability studies.

The rate and extent of absorption of a drug into the bloodstream is an important quality characteristic of a dosage form. In vivo bioavailability and in vitro dissolution studies are important in the development and ultimately in the quality control of a dosage form. The integrity of these tests is dependent on the analytical methods used. The advent of very potent drugs used in low dosage and the development of novel drug delivery systems require that the most sophisticated methods are used. This paper surveys recent trends in analytical advances that are useful in dissolution and bioavailability testing and suggests some future directions.

A high-performance liquid chromatographic assay for clindamycin phosphate and its principal degradation product in bulk drug and formulations.

A high-performance liquid chromatography method has been developed for the analysis of clindamycin phosphate and clindamycin, the principal degradation product. The method is quantitative, precise and is able to separate a variety of closely related molecules. The method has been applied to bulk drug, topical and sterile solutions, and experimental cream, lotion and gel formulations. The method gives results that are in good agreement with the official gas chromatographic method but is much less time-consuming.

Cytosine arabinoside stability in intravenous admixtures with sodium bicarbonate and in plastic syringes.

The increased use of high-dose cytarabine in the treatment of neoplasms prompted this study on the reconstituted stability of cytarabine in intravenous admixtures with sodium bicarbonate and in plastic syringes. The study of the effect of sodium bicarbonate was prompted by the frequent use of this agent in patients being treated with cytarabine as a means of achieving systemic alkalinization in order to manage hyperuricemia. The stability of reconstituted cytarabine in plastic syringes was measured to determine whether cytosine arabinoside could be reconstituted and stored prior to use. The results of this study indicate that sodium bicarbonate 50 mEq/L in the intravenous solution containing cytarabine has no effect on the chemical stability of cytarabine for at least one week at room temperature or in the refrigerator. Consequently sodium bicarbonate and cytarabine can be coadministered in one intravenous solution. The reconstituted stability of cytarabine at 20 mg/ml and 50 mg/ml is not affected by storage in plastic syringes.

Analysis of iodochlorhydroxyquin in cream formulations and bulk drugs by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the analysis of iodochlorhydroxyquin in creams and as bulk drugs has been developed. Iodochlorhydroxyquin was acetylated in the 8-position by reaction with acetic anhydride in pyridine. The resulting ester was mixed with the internal standard and chromatographed on a microparticulate silica column. Recovery was quantitative and the method was shown to be applicable to cream formulations from several manufacturers.

High-performance liquid chromatographic determination of hydrocortisone cypionate: method development and characterization of chromatographic behavior.

A reversed-phase high-performance liquid chromatographic method for hydrocortisone cypionate bulk drug and oral solution was developed that avoids the use of a heated column as described in USP XX. A study of the effect of the organic modifier concentration on the capacity factor suggests that mixed partition and adsorption phenomena are responsible for the retention of several steroids when acetonitrile is used in the mobile phase. Evidence is presented that hydrogen bonding of the solute molecule with silane hydroxyl groups may be responsible for the adsorption.

Determination of dextromethorphan hydrobromide by high-performance liquid chromatography using ion-pair formation.

The chromatographic retention behavior of dextromethorphan hydrobromide on an octadecylsilane column was investigated as a function of the pairing ion and the mobile phase composition. Dramatic increases in the capacity factor were observed with pairing ions containing more than eight carbons and with decreasing organic modifier (acetonitrile) concentration. Several pharmaceutically important amines exhibited similar behavior with respect to acetonitrile concentration. An analytical method was developed for dextromethorphan hydrobromide bulk drug and syrups and was applied to commercial preparations.

Evaluation of two lithium carbonate formulations.

An open, two-way crossover study of Latin-square design was used to compare the bioavailability of a new capsular formulation of lithium carbonate, Pfi-Lithium (Pfipharmecs Division, Pfizer, Inc.), with that of standard capsular formulation, Eskalith (Smith Kline & French Laboratories). Eighteen healthy, adult male volunteers received both formulations in a randomly determined order. After administration of each 300-mg dose of lithium carbonate, serial blood specimens were obtained. Data obtained from these specimens were subjected to pharmacokinetic evaluation. There were no significant differences (p less than 0.05) in peak plasma concentration, time to peak plasma concentration, and area under the plasma concentration-time curve. These single-dose suggested that the two formulations were bioequivalent.

High-performance liquid chromatographic analysis of codeine in syrups using ion-pair formation.

The chromatographic behavior of morphine, codeine, and ethylmorphine was examined using reversed-phase high-performance liquid chromatography and ion-pair formation. Alkyl sulfonates and sulfates significantly increased the retention times for these compounds. The carbon chain length of the pairing ions was linearly related to the log of the capacity factors of these amine drugs. A mechanism for the increased retention based on ion-pair formation in the mobile phase is proposed. The use of dioctyl sodium sulfosuccinate as a pairing ion for codeine is described, and a method utilizing this pairing ion was developed for the quantitation of codeine in syrups. This method was applied successfully to various syrups containing codeine or codeine phosphate.

Colorimetric determination of penicillins and related compounds in intravenous solutions by nickel (II)-catalyzed hydroxamic acid formation.

Solutions of ampicillin, carbenicillin, methicillin, oxacillin, penicillin G, and cephalothin in 5% dextrose were analyzed by nickel(II)-catalyzed hydroxylaminolysis. The reactions of these antibiotics were complete within 20 min at room temperature. Under the analytical conditions, molar absorptivities of the ferric-hydroxamate complexes ranged from 830 to 1005 liters/mole/cm. Coefficients of variation for the analysis of these antibiotics in 5% dextrose were typically less than 3% at concentrations of 1 mg/ml. Oxacillin was analyzed by the same method in normal saline and/or lactated Ringer solutions. The method also was applied to the analysis of chloramphenicol in aqueous solutions. Only ampicillin showed a significant decrease in concentration in 48 hr.

Direct determination of acetaminophen in plasma by differential pulse voltammetry.

A rapid, simple method for the direct determination of acetaminophen in plasma at toxic levels was developed. The method is based on the oxidation of the phenolic moiety of acetaminophen at a carbon paste electrode in a differential pulse voltammetric mode. Linear calibration curves are obtained from 20 to 400 microgram/ml. No sample cleanup is required.

Determination of theophylline in plasma by oxidation at the stationary carbon-paste electrode.

A method for the determination of the concentration of theophylline in plasma at therapeutic levels is described. The method is based on the oxidation of theophylline at the stationary carbon-paste electrode and involves a simple extraction procedure and differential pulse voltammetry. Possible interferences are discussed and typical calibration curves are presented.

Precautionary note for use of bisulfite in pharmaceutical formulations.

The effect of sodium bisulfite on aspirin hydrolysis was studied at 40 degrees in the pH range of 6.5-7.5. Significant catalytic activity by the sulfite ion was observed. Second-order rate constants were calculated for this catalysis and compared to other buffer species. The sulfite ion was a much more efficient catalyst than acetate, phosphate, or carbonate.

Colorimetric determination of aliphatic acids.

A colorimetric method for the determination of carboxylic acids based on the dicyclohexylcarbodiimide-coupled reaction of 2-nitrophenylhydrazine and carboxylic acids is described. The product of the reaction is extracted into aqueous sodium hydroxide to produce a blue color. This method is suitable for the analysis of aliphatic acids, but aromatic acids do not react under these conditions.