How to manage medications in the setting of liver disease with the application of six questions

OBJECTIVE

Reviewing the current literature to guide clinicians managing medications in the setting of liver disease.

LITERATURE SOURCES

Using the terms liver disease, medication management, and therapeutic monitoring, a literature review was conducted to identify peer-reviewed articles in MEDLINE (1966-April 2009). Reference citations were reviewed as an additional resource. Published English-language literatures, articles and trials were reviewed. Emphasis was placed on prospective, randomised, double-blind, placebo-controlled clinical trials.

QUESTION SYNTHESIS

An informed decision on how to manage medications in the setting of liver disease should account for changes that transpire in a medication's first-pass metabolism, protein binding, volume of distribution, clearance and pharmacodynamic interactions. To incorporate these issues within one's thought process, clinicians can utilise the following six questions to evaluate a medication use: (i) Is the patient experiencing acute or chronic liver failure? (ii) Does the drug have high hepatic first-pass metabolism? (iii) Is the medication highly protein-bound? (iv) Is there a change in the volume of distribution for the medication? (v) Is the clearance of the medication significantly altered? and (vi) Is there a pharmacodynamic interaction with the medication?

CONCLUSIONS

The introduction and use of six clinically relevant questions in the setting of liver disease can serve as a guide to clinicians who manage patients with liver disease.

Stability and visual compatibility of bretylium tosylate with selected large-volume parenterals and additives

The stability of bretylium tosylate when mixed with large-volume parenteral (LVP) solutions was assessed over a four-week period, and the compatibility of bretylium tosylate when mixed with eight frequently used drugs was evaluated. Bretylium tosylate admixtures of approximately 1 mg/ml were prepared in both polyvinyl chloride (PVC) bags and glass bottles of 5% dextrose injection, 0.9% sodium chloride injection, and lactated Ringer's injection. The admixtures were examined visually and stored for four weeks at 25 +/- 0.5 degree C under fluorescent light. The concentrations of bretylium tosylate were determined spectrophotometrically at times 0.25, 0.5, 1, 3, 8, 24, and 48 hours and twice weekly thereafter for four weeks. Spectrophotometric assays were confirmed with high-pressure liquid chromatography. Admixtures of bretylium tosylate were prepared with aminophylline, calcium gluconate, digoxin, regular insulin, lidocaine hydrochloride, phenytoin sodium, procainamide hydrochloride, and quinidine gluconate in 5% dextrose injection and 0.9% sodium chloride injection. The admixtures were examined visually for 48 hours. The concentration of bretylium tosylate did not change appreciably during the four-week study period. There were no signs of haze, precipitation, color change, or evolution of gas. There were no apparent differences in stability when comparing the glass with the PVC containers. Bretylium tosylate was also found to be compatible with all the additives tested except phenytoin sodium; a precipitate formed immediately when the latter drug was added to the bretylium tosylate solution. Bretylium tosylate was stable for four weeks in the LVP solutions studied in both glass and PVC containers. The admixtures of bretylium sodium with the other drugs were all visually compatible except those containing phenytoin sodium.

Compatibility of enteral products with commonly employed drug additives

Although drugs are routinely administered through gavage feedings set along with enteral products, there is little scientific data available to the physician, pharmacist, nurse, and dietician concerning the physical and chemical compatibility of drugs with enteral formulations. This study assesses the compatibility of Ensure (Ross Laboratories, Columbus, OH), Ensure Plus (Ross Laboratories, Columbus, OH), Osmolite (Ross Laboratories, Columbus, OH) with antibiotics, gastrointestinal agents, antipsychotic agents, urinary antiseptics cough and cold medications, and other commonly used additives. All enteral formulations were examined immediately after mixing for phase changes, creaming, and particle growth using a contrast light and a rotation viscometer. Results are presented in a tabular format. Guidelines and recommendations concerning how the addition of troublesome drug additives can be added are also presented.

Stability of dobutamine hydrochloride in selected large-volume parenterals

Stability of dobutamine hydrochloride when mixed with large-volume parenteral solutions was assessed. Dobutamine hydrochloride was added to large-volume solutions of 5% dextrose injection, 0.9% sodium chloride injection, lactated Ringer's injection, and 5% dextrose and 0.45% sodium chloride injection, in both glass and polyvinyl chloride containers; the initial concentration was 1 mg/ml. After 0.25, 1, 3, 8, 24, and 48 hours, the concentration of dobutamine hydrochloride was determined by high-pressure liquid chromatography assay, and each solution was visually examined for evidence of haze, precipitation, color change, or evolution of gas. Concentration of dobutamine hydrochloride in the samples did not exhibit any appreciable change over the 48-hour period, and no HPLC peaks indicating degradation products were noted. Color changes were observed in some of the solutions, but no other visual changes occurred. There were no apparent differences in stability between the admixtures packaged in glass and those in polyvinyl chloride bags. At the concentration studied, dobutamine hydrochloride is stable in the admixtures tested for a minimum of 48 hours.

Differential pulse polarography of some degradation products of tetracycline

In an attempt to develop a more rapid, convenient, and precise method for the direct detection and analysis of the degradation products of tetracycline, a study of those products utilizing differential pulse polarography was initiated. The investigation was concentrated on the subject of the kinetics of the epimerization of anhydrotetracycline to 4-epianhydrotetracycline in acetate buffer. The reaction was followed at 25 and 50 degrees. Duplicate experiments were run at each temperature. The apparent rate constants obtained were 4.17 +/- 0.13 X 10(-1)/hr (25 degrees) and 6.97 +/- 1.00 X 10(-2)/hr (50 degrees).

Stability and compatibility of lidocaine hydrochloride with selected large-volume parenterals and drug additives

The stability of lidocaine hydrochloride in six commonly used large-volume parenterals when stored for 14 days and the visual compatibility of lidocaine hydrochloride in admixtures with eight frequently used drugs were studied. Lidocaine hydrochloride admixtures of 2 mg/ml were prepared in both glass and plastic containers of 5% dextrose injection, 0.9% sodium chloride injection, lactated Ringer's injection, 5% dextrose and lactated Ringer's injection, 0.45% sodium chloride injection (plastic container only), and 0.45% sodium chloride and 5% dextrose injection. The admixtures were examined visually and stored for 14 days at 25 +/- 0.5 degrees C under fluorescent light. Lidocaine hydrochloride concentrations were determined spectrophotometrically at times 0, 0.25, 1, 3, 8, and 24 hours, and at 24-hour intervals thereafter. Spectrophotometric assays were confirmed with high-pressure liquid chromatography. Admixtures of lidocaine hydrochloride were prepared with aminophylline, bretylium tosylate, calcium gluconate, digoxin, dopamine hydrochloride, regular insulin, phenytoin sodium, and procainamide hydrochloride in 5% dextrose injection, 0.9% sodium chloride injection, and lactated Ringer's injection. The admixtures were examined visually for 24 hours. Admixtures of lidocaine hydrochloride were stable for 14 days. All admixtures of lidocaine hydrochloride with other drugs were visually compatible except those containing phenytoin sodium. It is concluded that lidocaine hydrochloride is stable in the solutions studied for 14 days at 25 degrees C and visually compatible for 24 hours in admixtures containing all drugs studied except phenytoin sodium.

In vitro adsorption studies of cimetidine

The adsorption of cimetidine on selected pharmaceuticals including kaolin, activated charcoal, talc, and nonsystemic antacids was determined at pH 5.0 and 25 degrees. The Langmuir and Freundlich adsorption isotherms showed that cimetidine adsorption was significant with activated charcoal, kaolin, talc, and magnesium trisilicate and was virtually nonexistent with magnesium hydroxide and aluminum hydroxide. Equations expressing the Freundlich and Langmuir adsorption isotherms were evaluated for each adsorbent. The approximate amounts of cimetidine adsorbed per gram of adsorbent were 25.6, 0.402, 0.291, and 0.343 mg for charcoal, kaolin, talc, and magnesium trisilicate, respectively. These in vitro studies indicate that some cimetidine may be lost when it is administered concomitantly with pharmaceutical adsorbents.