Antipyrine pharmacokinetics and D-glucaric excretion in kwashiorkor

A systematic review of pharmacokinetics studies in children with protein-energy malnutrition

OBJECTIVE

protein energy malnutrition (PEM) is a nutritional problem affecting many children world-wide. Its association with a wide spectrum of infections necessitates multiple drug therapies. A systematic review was performed to determine the effects of PEM on drug pharmacokinetics.

METHODS

literature searches in the MEDLINE and EMBASE databases (January 1960 to December 2009) were performed. Malnutrition, undernutrition, underweight, protein-energy malnutrition, protein-calorie malnutrition, marasmus, marasmic-kwashiorkor or kwashiorkor was the medical subject heading (MeSH) descriptor used. Inclusion criteria were abstracts that assessed or discussed absorption, distribution, metabolism, elimination, clearance, pharmacokinetics or pharmacodynamics of drugs, except micronutrients and appetite-stimulating drugs.

RESULTS

altogether, 41 publications were identified. A total of 34 drugs were studied. The absorption of 18 drugs was studied; the extent of absorption (AUC) was unaffected for 10 drugs. The plasma protein binding of 20 drugs was evaluated; it was significantly reduced for 12 drugs. The volume of distribution (Vd) of 13 drugs was evaluated; it was, however, unaffected for most of the drugs. The effect of PEM on total clearance and the half-life of drugs primarily metabolised by the liver was studied for 8 drugs. There was decreased total clearance and an associated increased half-life of 5 drugs. For 2 drugs (chloramphenicol and quinine), different degrees of PEM affected total clearance differently. The total clearance of six drugs primarily eliminated by the kidneys was studied; it was unaffected for four drugs, but significantly decreased for two drugs (cefoxitin and penicillin).

CONCLUSIONS

considering the proportion of children affected with PEM world-wide, there have been relatively few pharmacokinetic studies of drugs frequently used for their treatment. More studies are therefore required to establish the appropriate dose and safety of these drugs for PEM children. The studies need to recognise that PEM is a disease spectrum and should further look at the differential effects of kwashiorkor and marasmus on drug pharmacokinetics in children.

Effects of protein calorie malnutrition on the pharmacokinetics of ketamine in rats

The effect of protein calorie malnutrition (PCM) on the pharmacokinetics of ketamine (KET) enantiomers has been investigated. Six control and six PCM rats were administered 85 mg/kg racemic KET by intramuscular injection, and plasma concentrations of (S)- and (R)-KET, norketamine (NKET), and 5,6-dehydronorketamine (DNK) were measured using enantioselective gas chromatography. Pharmacokinetic profiles were analyzed using standard noncompartmental and compartmental modeling methods. The volumes of distribution were similar between control and PCM rats for (S)- and (R)-KET. However, total clearance of both KET enantiomers was decreased, resulting in an increase in systemic exposure (p < 0.05). The KET absorption rate was also increased in PCM rats. A decrease in the clearance of both NKET enantiomers led to a significant increase in exposure in PCM rats (p < 0.005), and modeling results could not exclude the possibility that PCM induced an increase in the fraction of KET following the NKET pathway, which may further contribute to this increase in exposure. An increase in exposure to DNK enantiomers was also evident in PCM animals compared with controls [p < 0.005 (DNK1); N.S. (DNK2)], which was in concordance with the decrease in apparent clearance values. These results show that PCM significantly alters the pharmacokinetics of KET and several of its metabolites.

Pharmacokinetic changes in drugs during protein-calorie malnutrition: correlation between drug metabolism and hepatic microsomal cytochrome p450 isozymes

The rats with protein-calorie malnutrition (PCM, 5% casein diet for a period of 4-week) were reported to exhibit 60 and 80% suppression in the hepatic microsomal cytochrome P450 (CYP) 1A2 and CYP2C11 levels, respectively, and 40-50% decreases in CYP2E1 and CYP3A1/2 levels compared to control (23% casein diet for a period of 4-week) based on Western blot analysis. In addition, Northern blot analysis showed that CYP1A2, CYP2E1, CYP2C11, and CYP3A1/2 mRNAs decreased in the state of PCM as well. Hence, pharmacokinetic changes of the drugs in rats with PCM [especially the area under the plasma concentration-time curve from time zero to time infinity (AUC) changes of metabolite(s)] reported from literatures were tried to explain in terms of CYP isozyme changes in the rats. Otherwise, the time-averaged nonrenal clearance (CL NR) of parent drug was compared. Pharmacokinetic changes of the drugs in other types of malnutritional state, such as kwashiorkor and marasmus, in both human and animal models were also compared. The drugs reviewed are as follows: diuretics, antibiotics, anticancer agents, antiepileptics, antiarrythmics, analgesics, xanthines, antimalarials, and miscellaneous.

Effect of protein-calorie malnutrition on cytochromes P450 and glutathione S-transferase

Protein-calorie malnutrition (PCM) can develop both from inadequate food intake and as a consequence of diseases such as cancer and AIDS. Several studies have shown that PCM can alter drug clearance but little information is available on the effect of PCM on individual cytochrome P450 isoforms and phase II conjugation enzymes. The aim of the present study was to begin a systematic evaluation of the effect of PCM on the activity of individual drug metabolizing enzymes in a rat model of PCM. Control and PCM rats received isocaloric diets which contained either 21% or 5% (deficient) protein. After 3 weeks, the animals were sacrificed and microsomal and cytosolic fractions prepared. Ethoxyresorufin O-deethylation (EROD), chlorzoxazone 6-hydroxylation, dextromethorphan N- and O-demethylation and 1-chloro-2,4-dinitrobenzene (CDNB) conjugation were used as measures of CYP1A, CYP2E1, CYP3A2, CYP2D1 and glutathione S-transferase (GST) activity, respectively. Additionally, NADPH-cytochrome P450 reductase activity was measured in the liver microsomes. PCM significantly reduced the maximum velocity (Vmax) of all model reactions studied. However, differential effects were observed with respect to K(m) values of the reactions. The K(m) values for EROD and dextromethorphan N-demethylation were significantly increased in PCM animals, whereas the K(m) values for chlorzoxazone 6-hydroxylation and dextromethorphan O-demethylation were decreased. In contrast, the K(m) value for CDNB conjugation was unchanged. When NADPH-cytochrome P450 reductase activity was compared, a 29% reduction in reductase activity was noted in PCM animals as compared to controls. Thus, it appears that PCM decreases the overall activity of certain phase I and phase II metabolism enzymes in rat liver while exhibiting differential effects on K(m). Furthermore, this reduction in activity may be due in part to diminished activity of cytochrome P450 reductase.

Impact of nutrition on pharmacokinetics of anti-neoplastic agents

It has been estimated that approximately 80% of the world's pediatric population lives in countries with limited resources, and that 43% of these children are malnourished. In children with cancer, malnutrition may antedate the diagnosis or be a result of aggressive chemotherapeutic regimens. Studies have shown that children with cancer and malnutrition have a less favorable prognosis, a higher risk of early relapse, and tolerate chemotherapy poorly when compared with children with normal nutritional status. Improvements in nutritional status may improve tolerance to chemotherapy. An understanding of the mechanisms responsible for the effects of malnutrition on drug disposition and pharmacodynamic response is important, especially for anti-neoplastic agents, which have a narrow therapeutic index and may be associated with potentially severe or life-threatening side-effects. Several factors related to malnutrition have been suggested to alter drug disposition. Diminished protein "status" in malnourished children results in lower amounts of plasma proteins, increasing the concentration of free drug available to exert its cytotoxic effect. Severely malnourished individuals also exhibit decreased oxidative metabolism and reduced glomerular filtration rate (GFR), potentially increasing concentrations of parent drug or active metabolites. Malnourished children receiving chemotherapy for the treatment of an underlying malignancy may need specifically "tailored" protocols to achieve therapeutic response while minimizing adverse acute and long-term side effects. The role of specific interventions, such as correction of nutritional status or pharmacokinetic drug monitoring, should be evaluated in this context.

Influences of diet and nutrition on clinical pharmacokinetics

The human diet represents a complex and variable mixture of nutrients, many of which have the potential for altering the disposition of drugs. This review highlights progress from a number of laboratories illustrating nutrient influences on drug dispositions and actions. Emphasis is placed on nutritional effects on hepatic drug metabolism studied in humans. Data from animals have sometimes been difficult to extrapolate to humans, as illustrated by reports on the influences of starvation, dietary lipids, and ascorbic acid. From studies in healthy subjects it is now clear that a number of specific dietary factors can influence drug metabolism by the mixed function oxidase system and conjugating enzymes. These include dietary protein, cruciferous vegetables, charcoal-broiled beef containing polycyclic aromatic hydrocarbons, and methylxanthines. The effects of such dietary components have been demonstrated for only a limited number of drug substrates for these enzyme systems. Effects of food on bioavailability have been more widely studied, and depend greatly upon the type of drug. Malnutrition can be associated with variable but potentially important effects on the bioavailability, binding, hepatic metabolism, and renal clearance of drugs. In malnourished patients it is generally difficult to recognise the roles of individual nutrient deficiencies on drug disposition, and clinical predictors of altered pharmacokinetics for various drugs in such patients are not well defined. It is likely that many important interrelationships between nutrition and new or already marketed drugs remain to be recognised, and therefore warrant further research. Nutritional effects on drug metabolising enzymes also have implications for endogenous substances such as hormones and environmental toxins and carcinogens which are metabolised by the same or related enzyme systems, and for diseases likely to be related to the actions of such chemicals.

An evaluation of the low-pH enzymatic assay of urinary D-glucaric acid, and its use as a marker of enzyme induction in exocrine pancreatic disease

We have evaluated a low-pH enzymatic method for measuring urinary D-glucaric acid, and its usefulness as a marker of 'enzyme induction' in patients with exocrine pancreatic disease. The coefficient of variation lay between 7.5 and 10.9% for within-batch precision, and between 7.9 and 19.8% for between-batch precision. The useful range of the method was 20-200 mumol/l, with a lower detection limit of 11 mumol/l. The molar concentration ratio of D-glucaric acid to creatinine in urine correlated with the 8-h output of D-glucaric acid (p less than 0.005): both indices were significantly higher in a group of 29 patients with exocrine pancreatic disease than in controls (median ratios 4.6 and 2.9 X 10(-3), p less than 0.005; median outputs 14.0 and 8.8 mumol/8 h, respectively, p less than 0.005). Comparison with the results of theophylline tests in the same group of patients showed that whereas 72% of patients had theophylline clearances higher than the highest value in controls, 45% of the group had increased D-glucaric acid/creatinine ratios, whilst only 21% had increased outputs of D-glucaric acid. Paradoxically, in patients with established liver disease in whom drug metabolism was impaired urinary D-glucaric acid values were amongst the highest encountered in the study. Thus, the obvious advantages of the method--non-invasive, simple, reproducible, inexpensive, easily applied to out-patients--are offset by an unacceptably low predictive value as an indicator of microsomal 'enzyme induction'.

Stimulation of oxidative drug metabolism by parenteral refeeding of nutritionally depleted patients

To determine whether intravenous nutritional repletion can influence oxidative drug metabolizing capacity, antipyrine metabolism was studied in 6 malnourished patients on the second day of a 2-day baseline period and on the last day of two sequential, 8-day intravenous nutritional repletion periods. During the baseline period they received 5% dextrose, 440 kcal per day, intravenously. During the repletion periods they received 20 mg of nitrogen per kilocalorie of baseline resting energy expenditure and, in random order, dextrose to provide a total caloric intake of either 0.95 or 1.75 times baseline resting energy expenditure. There were no statistically significant differences between the high- and low-dextrose repletion regimens in their effects on antipyrine metabolism. Seven days of nutritional repletion resulted in a 42% decrease in mean half-life (range 12%-52%) and an 87% increase in mean metabolic clearance rate (range 29%-155%) for antipyrine. An additional 8 days of nutritional repletion resulted in no further change in these pharmacokinetic parameters.

Pharmacokinetics of theophylline in protein-calorie malnutrition

The influence of protein-calorie malnutrition (PCM) on the disposition of theophylline was investigated in male Sprague-Dawley rats fed for four weeks on a 23 per cent (control) or 5 per cent (low) protein diet ad lib. Dietary protein deficiency led to a decrease in body weight gain, plasma proteins, albumin, microsomal proteins, and cytochrome P-450. After intravenous administration of aminophylline equivalent to 10 mg kg-1 theophylline, the average mean residence time (MRT) was 58 per cent higher in the protein-deficient rats, while the total plasma clearance (Cl) per kilogram of body weight and elimination rate constant (k) were decreased by 39 per cent and 45 per cent, respectively, when compared to rats on a normal protein diet. No significant difference was found in the two groups of animals with respect to the apparent steady-state volume of distribution (Vss). The present results suggest that the mechanism responsible for the observed pharmacokinetic changes in the protein-deficient rats is related to the reduced amount and/or activity of the hepatic mixed function oxidases.

Absence of a pharmacokinetic interaction between chloramphenicol and acetaminophen in children

The pharmacokinetics of chloramphenicol (CAP; administered intravenously as chloramphenicol succinate, CAPS) was studied in 26 acutely ill febrile children 3 to 58 months of age who either did (n = 18) or did not (n = 8) receive acetaminophen (APAP) for antipyresis. CAP pharmacokinetics were evaluated after the first dose and at steady state. CAP serum levels were quantitated by high-performance liquid chromatography. There were no significant differences between groups (APAP vs non-APAP) or between first dose and steady-state evaluations for the elimination rate constant, serum half-life, apparent volume of distribution, and serum clearance of CAP. Likewise, there were no statistically significant differences when the APAP group was evaluated according to the presence or absence of APAP in serum before the first dose of CAP. Elimination of CAP in subjects with serum CAPS level less than 1 microgram/ml was similar in the first dose and steady-state evaluations and in the APAP and non-APAP groups. The presence or absence of CAPS or APAP did not affect the estimation of CAP elimination. Thus a pharmacokinetic interaction between CAP and APAP was not demonstrated in acutely ill febrile children during concomitant therapy.

The elderly, undernutrition, and pharmacokinetics

There is good evidence that malnutrition may alter the pharmacokinetic parameters and, thus, actions of several drugs. The elderly are probably most at risk, as malnutrition tends to affect factors already altered by primary and secondary aging.

Antipyrine metabolite formation in children in the acute phase of malnutrition and after recovery

1. The plasma elimination rate of antipyrine and the urinary excretion of antipyrine and its primary metabolites 4-hydroxy-antipyrine, norantipyrine, 3-hydroxymethyl-antipyrine and 3-carboxyantipyrine were measured in five children in the acute phase of malnutrition and after recovery. The results were compared with those obtained in 3 normal children. 2. Upon nutritional rehabilitation antipyrine clearance increased from 0.65 +/- 0.14 ml min-1 kg-1 to 1.07 +/- 0.20 ml min-1 kg-1. 3. The urinary excretion of 4-hydroxy-antipyrine increased from 6.1 +/- 4.5 to 14.7 +/- 5.9%, norantipyrine from 8.8 +/- 5.7 to 14.3 +/- 5.4 and 3-hydroxy-methyl-antipyrine from 11.8 +/- 8.3 to 20.5 +/- 5.6% (% of dose/24h urine). Excretion of unchanged antipyrine decreased from 5.2 +/- 3.7 to 2.7 +/- 0.9% dose. The metabolite profile (ratio between the amounts of the various metabolites excreted) was not significantly different. 4. It is concluded that malnutrition decreases the rate of antipyrine metabolism, but it does not affect the three oxidative pathways differently.