The effect of short-term starvation or water deprivation on caffeine pharmacokinetics in calves

Effects of starvation on the pharmacokinetics and optimal dosages of florfenicol and associated serum biochemistry in Asian seabass (Lates calcarifer)

Starvation has influence on physiology and pharmacokinetic (PK) characteristics of many drugs in land animals. However, similar PK information in fish is lacking. The current study examined the effects of starvation on fish PK, taking florfenicol (FF) in Asian seabass as an example. FF was orally administered at a single dose of 10 mg/kg into 35-day starved fish reared at 25 and 30°C and the serum FF concentration was analyzed by HPLC-FLD. At 30°C, the absorption and elimination half-lives of the starved fish were increased by 30% (from 0.44 to 0.57 h) and 55% (from 7.2 to 11.18 h), respectively. The volume of distribution, clearance, and area under the curve were changed from 1.25 to 0.71 L/kg, 0.120 to 0.044 L/kg/h, and 88 to 228 h·μg/ml, respectively. Similar starvation-induced PK changes were also observed at 25°C. The serum biochemical parameters, mainly the alanine aminotransferase, aspartate aminotransferase, and glucose levels, were significantly reduced in the starvation group. Overall, FF absorption, distribution, and elimination rates were reduced by starvation, resulting in four to five times lower optimal dosage than the non-starved fish. Drug treatment in starved fish should be treated with caution as overdosing and/or tissue residues could perceivably occur.

Transcriptional responses to starvation stress in the hepatopancreas of oriental river prawn Macrobrachium nipponense

Various crustaceans are farmed using aquaculture, and food deprivation or fasting can occur due to changing of environmental or management strategies. However, the molecular mechanisms underlying responses to starvation in crustaceans remain unclear. To address this, 12 hepatopancreas transcriptomes were compared for oriental river prawn (Macrobrachium nipponense) from four fasting stages (0, 7, 14 and 21 d). Gene Ontology functional annotation and Kyoto Encyclopaedia of Genes and Genomes pathway enrichment analysis of differentially expressed genes were subsequently performed. During the early stages of starvation (0-7 d), drug metabolism via the cytochrome P450 pathway and metabolism of xenobiotics by the cytochrome P450 pathway were enriched, suggesting that they metabolised compounds generated under starvation stress. As starvation proceeded (7-14 d), the retinol (vitamin A) metabolism pathway was activated, based on three up-regulated genes (CYP3, ADH and UGT), along with the two p450 pathways. Meanwhile, vitamin A was gradually consumed. As acute starvation was reached (14-21 d), vitamin A deficiency decreased the mRNA expression levels of IGF-I that is involved in the mTOR signalling pathway, which ultimately affected the growth and development of M. nipponense. Our results implicate drug/xenobiotic metabolism by cytochrome P450s in adaptation to starvation stress. Furthermore, metabolic cascades (CYP and retinol pathways) and growth (mTOR signalling) pathways are clearly triggered in crustaceans during starvation. The findings expand our understanding of the genes associated with hepatopancreas functioning in M. nipponense, and the underlying molecular mechanisms that govern the responses of crustaceans to starvation stress.

Measurements of caffeine and plasma metabolite/caffeine ratios as a test for hepatic drug-oxidizing capacity in goats

The aim of this investigation was to determine the pharmacokinetics and demethylation of caffeine (CF) and the metabolite/CF ratios that correlated best with CF clearance, which were used to evaluate hepatic drug-oxidizing capacity of CF after a single intravenous dose (5 mg/kg) in hair goats (n = 9). Pharmacokinetic parameters of CF and its metabolites, theobromine (TB), paraxanthine (PX) and theophylline (TP), were calculated. The plasma metabolic ratios TB/CF, PX/CF, TP/CF and TB+PX+TP/CF were determined at 6, 8 and 10 h after CF administration to evaluate their hepatic drug-oxidizing capacity. The plasma concentration-time data of CF were fit to a two-compartment model in all animals. The clearance of CF was 0.08 ± 0.02 L/h/kg, and the volume of distribution was 0.91 ± 0.16 L/kg. The demethylation fractions of CF to TB, PX and TP were 0.24, 0.37 and 0.39, respectively. Correlations between the metabolic ratios and CF clearance were quite high, except for the PX/CF ratio, particularly at 6 h (r = 0.650-0.750, P < 0.01, 0.05) and 10 h (r = 0.650-0.767, P < 0.01, 0.05). Plasma metabolite/CF ratios, except for the PX/CF ratio, may be useful as an alternative to measurements of CF clearance for the determination of the hepatic drug-oxidizing capacity in goats.

Evaluation of the reproductive and developmental risks of caffeine

A risk analysis of in utero caffeine exposure is presented utilizing epidemiological studies and animal studies dealing with congenital malformation, pregnancy loss, and weight reduction. These effects are of interest to teratologists, because animal studies are useful in their evaluation. Many of the epidemiology studies did not evaluate the impact of the "pregnancy signal," which identifies healthy pregnancies and permits investigators to identify subjects with low pregnancy risks. The spontaneous abortion epidemiology studies were inconsistent and the majority did not consider the confounding introduced by not considering the pregnancy signal. The animal studies do not support the concept that caffeine is an abortafacient for the wide range of human caffeine exposures. Almost all the congenital malformation epidemiology studies were negative. Animal pharmacokinetic studies indicate that the teratogenic plasma level of caffeine has to reach or exceed 60 µg/ml, which is not attainable from ingesting large amounts of caffeine in foods and beverages. No epidemiological study described the "caffeine teratogenic syndrome." Six of the 17 recent epidemiology studies dealing with the risk of caffeine and fetal weight reduction were negative. Seven of the positive studies had growth reductions that were clinically insignificant and none of the studies cited the animal literature. Analysis of caffeine's reproductive toxicity considers reproducibility and plausibility of clinical, epidemiological, and animal data. Moderate or even high amounts of beverages and foods containing caffeine do not increase the risks of congenital malformations, miscarriage or growth retardation. Pharmacokinetic studies markedly improve the ability to perform the risk analyses.

Patient variation in veterinary medicine--part II--influence of physiological variables

In veterinary medicine, the characterization of a drug's pharmacokinetic properties is generally based upon data that are derived from studies that employ small groups of young healthy animals, often of a single breed. In Part I of the series, we focused on the potential influence of disease processes, stress, pregnancy and lactation on drug pharmacokinetics. In this Part II of the series, we consider other covariates, such as gender, heritable traits, age, body composition, and circadian rhythms. The impact of these factors with respect to predicting the relationship between dose and drug exposure characteristics within an animal population is illustrated through the use of Monte Carlo simulations. Ultimately, an appreciation of these potential influences will improve the prediction of situations when dose adjustments may be appropriate.

Pharmacokinetics of intravenously administered caffeine in healthy alpacas (Lama pacos) and llamas (Lama glama)

OBJECTIVE

To determine the pharmacokinetic disposition of IV administered caffeine in healthy Lama spp camelids.

ANIMALS

4 adult male alpacas and 4 adult female llamas.

PROCEDURES

Caffeine (3 mg/kg) was administered as an IV bolus. Plasma caffeine concentrations were determined by use of high-performance liquid chromatography in 6 animals and by use of liquid chromatography-mass spectrometry in 2 llamas.

RESULTS

Median elimination half-life was 11 hours (range, 9.3 to 29.8 hours) in alpacas and 16 hours (range, 5.4 to 17 hours) in llamas. The volume of distribution at steady state was 0.60 L/kg (range, 0.45 to 0.93 L/kg) in alpacas and 0.75 L/kg (range, 0.68 to 1.15 L/kg) in llamas. Total plasma clearance was 44 mL/h/kg (range, 24 to 56 mL/h/kg) in alpacas and 42 mL/h/kg (range, 30 to 109 mL/h/kg) in llamas.

CONCLUSIONS AND CLINICAL RELEVANCE

High-performance liquid chromatography and liquid chromatography-mass spectrometry were suitable methods for determination of plasma caffeine concentrations in alpacas and llamas. Plasma caffeine concentration-time curves were best described by a 2-compartment model. Elimination half-lives, plasma clearance, volume of distribution at steady state, and mean residence time were not significantly different between alpacas and llamas. Intravenous administration of caffeine at a dose of 3 mg/kg did not induce clinical signs of excitement.

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.

The effect of food or water deprivation on paracetamol pharmacokinetics in calves

This study investigated the effect of food or water deprivation on the pharmacokinetics of paracetamol in 30 Holstein-Friesian preruminant calves (10 controls, 10 food withheld and 10 water-deprived) aged 24-25 days. Control calves were given paracetamol at 24-25 days and again at 28-29 days of age. In the food withheld and water-deprived calves paracetamol studies were performed before and after 4 days of food or water deprivation. In the control group there were no significant differences in pharmacokinetic parameters for paracetamol in 24-25 and 28-29-day-old calves. Witholding food for 4 days was associated with an increase in the mean residence time (MRT) of paracetamol (P < 0.01). When food was withheld total body clearance (ClB) of paracetamol was significantly decreased (P < 0.05). The volume of distribution (Vss) was not significantly altered. Similarly, water deprivation was associated with a significant increase in MRT and significant decrease in ClB of paracetamol (P < 0.01). The Vss was not significantly altered. Food or water deprivation also influenced the formation of major metabolites (glucuronide and sulphate) of paracetamol. It is concluded that food or water deprivation may impair the elimination drugs that undergo metabolism by UDP-glucuronyltransferase and sulphotransferase in cattle.