Propofol metabolism is enhanced after repetitive ketamine administration in rats: the role of cytochrome P-450 2B induction

Sex effects on behavioral markers of emergence from propofol and isoflurane anesthesia in rats

Clinical studies have demonstrated sex-related differences in recovery from surgical anesthesia. This study aimed to characterize the emergence pattern following two anesthesia regimens in both sexes of rats. We considered six different markers of emergence from anesthesia: sigh, eye blinking, forelimb movement, mastication, neck extension, and recovery of the righting reflex (RORR). Spontaneous motor activity 24 h after the anesthesia induction was also examined. Our results showed that the rank order of the emergence latency after intraperitoneal propofol, PRO, exposure was forelimb movement < sigh < blink < mastication < neck extension < RORR, while after inhaled isoflurane, ISO, anesthesia the sequence was changed as sigh < blink < mastication < forelimb movement < neck extension < RORR in both male and female rats. Moreover, the latency to emergence after PRO in female rats was significantly higher than male rats, although following ISO there was no difference between the sexes (P < 0.001; P > 0.05, respectively). Open-field testing revealed no difference in PRO and ISO spontaneous locomotor activity due to drug administration (P > 0.05). These two anesthetics presented different emergence sequences. Although clinical data suggests that females arouse faster than males from anesthesia with propofol, our intraperitoneal technique in a rodent model had the opposite effect. Pharmacokinetic analysis demonstrated increased absorption of injected propofol for the female rats in our study, emphasizing the role of sexual dimorphism in drug distribution in rodents. Despite these pharmacokinetic differences, the pharmacodynamic effects of the drugs were remarkably consistent among both sexes through emergence.

Pharmacokinetics of ketamine and propofol combination administered as ketofol via continuous infusion in cats

The pharmacokinetics of the extemporaneous combination of low doses of ketamine and propofol, known as 'ketofol', frequently used for emergency procedures in humans to achieve safe sedation and analgesia was studied in cats. The study was performed to assess propofol, ketamine and norketamine kinetics in six female cats that received ketamine and propofol (1:1 ratio) as a loading dose (2 mg/kg each, IV) followed by a continuous infusion (10 mg/kg/h each, IV, 25 min of length). Blood samples were collected during the infusion period and up to 24 h afterwards. Drug quantification was achieved by HPLC analysis using UV-visible detection for ketamine and fluorimetric detection for propofol. The pharmacokinetic parameters were deduced by a two-compartment bolus plus infusion model for propofol and ketamine and a monocompartmental model for norketamine. Additional data were derived by a noncompartmental analysis. Propofol and ketamine were quantifiable in most animals until 24 and 8 h after the end of infusion, respectively. Propofol showed a long elimination half-life (t(1/2λ2) 7.55 ± 9.86 h), whereas ketamine was characterized by shorter half-life (t(1/2λ2) 4 ± 3.4 h) owing to its rapid biotransformation into norketamine. The clinical significance of propofol's long elimination half-life and low clearance is negligible when the drug is administered as short-term and low-dosage infusion. The concurrent administration of ketamine and propofol in cats did not produce adverse effects although it was not possible to exclude interference in the metabolism.

Absorption, distribution, metabolism and excretion pharmacogenomics of drugs of abuse

Pharmacologic and toxic effects of xenobiotics, such as drugs of abuse, depend on the genotype and phenotype of an individual, and conversely on the isoenzymes involved in their metabolism and transport. The current knowledge of such isoenzymes of frequently abused therapeutics such as opioids (oxycodone, hydrocodone, methadone, fentanyl, buprenorphine, tramadol, heroin, morphine and codeine), anesthetics (γ-hydroxybutyric acid, propofol, ketamine and phencyclidine) and cognitive enhancers (methylphenidate and modafinil), and some important plant-derived hallucinogens (lysergide, salvinorin A, psilocybin and psilocin), as well as of nicotine in humans are summarized in this article. The isoenzymes (e.g., cytochrome P450, glucuronyltransferases, esterases and reductases) involved in the metabolism of drugs and some pharmacokinetic data are discussed. The relevance of such data is discussed for predicting possible interactions with other xenobiotics, understanding pharmacokinetic behavior and pharmacogenomic variations, assessing toxic risks, developing suitable toxicological analysis procedures, and finally for interpretating drug testing results.

Induction of CYP1A1, 2B, 2E1 and 3A in rat liver by organochlorine pesticide dicofol

The present study has determined the ability of dicofol, an organochlorine pesticide, to induce cytochrome P450 using rats treated with 1, 10, and 25mg/kg dicofol intraperitoneally for 4 days. Treatments with 10 and 25mg/kg dicofol produced dose-related increases of cytochrome P450 and cytochrome b(5) contents and NADPH-cytochrome c reductase, 7-ethoxyresorufin O-deethylase, pentoxyresorufin O-dealkylase, aniline hydroxylase, and erythromycin N-demethylase activities in liver microsomes. The treatments also increased glutathione S-transferase and superoxide dismutase activities in liver cytosol. Dicofol at 1mg/kg produced a general trend towards increases of the aforementioned enzyme levels. The results of immunoblot analyses showed that 10 and 25mg/kg dicofol increased protein levels of CYP1A1, CYP2B, CYP2E1, and 3A in liver. RT-PCR data indicated that dicofol induced mRNA expression of liver CYP1A1, CYP2B, and CYP3A. Pretreatments of rats with 10 and 25mg/kg dicofol decreased phenobarbital-induced sleeping time by 34% and 39%, respectively. Dicofol pretreatment at 25mg/kg increased CCl4-induced serum alanine aminotransferase activity by 4.3-fold and aspartate aminotransferase activity by 4.1-fold. The present study demonstrates that dicofol has the ability to induce CYP1A1, CYP2B, CYP2E1, and CYP3A in the liver and increase phenobarbital metabolism and CCl4 toxicity in rats.

Cytoskeleton interruption in human hepatoma HepG2 cells induced by ketamine occurs possibly through suppression of calcium mobilization and mitochondrial function

Ketamine is an intravenous anesthetic agent often used for inducing and maintaining anesthesia. Cytoskeletons contribute to the regulation of hepatocyte activity of drug biotransformation. In this study, we attempted to evaluate the effects of ketamine on F-actin and microtubular cytoskeletons in human hepatoma HepG2 cells and its possible molecular mechanisms. Exposure of HepG2 cells to ketamine at <or=100 microM, which corresponds to clinically relevant concentrations for 1, 6, and 24 h, did not affect cell viability. Meanwhile, administration of therapeutic concentrations of ketamine obviously interrupted F-actin and microtubular cytoskeletons. In parallel, levels of intracellular calcium concentration- and time-dependently decreased after ketamine administration. Analysis by confocal microscopy further revealed that ketamine suppressed calcium mobilization from an extracellular buffer into HepG2 cells. Exposure to ketamine decreased cellular ATP levels. The mitochondrial membrane potential and complex I NADH dehydrogenase activity were both reduced after ketamine administration. Ketamine did not change the production of actin or microtubulin mRNA in HepG2 cells. Consequently, ketamine-caused cytoskeletal interruption led to suppression of CYP3A4 expression and its metabolizing activity. Therefore, this study shows that therapeutic concentrations of ketamine can disrupt F-actin and microtubular cytoskeletons possibly through suppression of intracellular calcium mobilization and cellular ATP synthesis due to down-regulation of the mitochondrial membrane potential and complex I enzyme activity. Such disruption of the cytoskeleton may lead to reductions in CYP3A4 activity in HepG2 cells.