Circadian Time‐Effect of Orally Administered Loratadine on Plasma Pharmacokinetics in Mice

Recent advances in circadian-regulated pharmacokinetics and its implications for chronotherapy

Dependence of pharmacokinetics and drug effects (efficacy and toxicity) on dosing time has long been recognized. However, significant progress has only recently been made in our understanding of circadian rhythms and their regulation on drug pharmacokinetics, efficacy and toxicity. This review will cover the relevant literature and a series of publications from our work summarizing the effects of circadian rhythms on drug pharmacokinetics, and propose that the influence of circadian rhythms on pharmacokinetics are ultimately translated into therapeutic effects and side effects of drugs. Evidence suggests that daily rhythmicity in expression of drug-metabolizing enzymes and transporters necessary for drug ADME (absorption, distribution, metabolism and excretion) are key factors determining circadian pharmacokinetics. Newly discovered mechanisms for circadian control of the enzymes and transporters are covered. We also discuss how the rhythms of drug-processing proteins are translated into circadian pharmacokinetics and drug chronoefficacy/chronotoxicity, which has direct implications for chronotherapy. More importantly, we will present perspectives on the challenges that are still needed for a breakthrough in translational research. In addition, knowledge of the circadian influence on drug disposition has provided new possibilities for novel pharmacological strategies. Careful application of pharmacokinetics-based chronotherapy strategies can improve efficacy and reduce toxicity. Circadian rhythm-mediated metabolic and transport strategies can also be implemented to design drugs.

Pharmacokinetics and Tissue Distribution of Loratadine, Desloratadine and Their Active Metabolites in Rat based on a Newly Developed LC-MS/MS Analytical Method

Loratadine (LOR) and its major metabolite, desloratadine (DL) are new-generation antihistamines. The hydroxylated metabolites of them, 6-OH-DL, 5-OH-DL and 3-OH-DL are also active because of their ability to inhibit binding of pyrilamine to brain H₁ receptors and a tendency for distributing to specific immune-regulatory tissues. In this study, a new validated LC-MS/MS method to simultaneously quantify LOR, DL, 6-OH-DL, 5-OH-DL and 3-OH-DL in plasma and tissues was established and applied to an investigation of their pharmacokinetics and target-tissue distribution tendency for the first time. Pharmacokinetics parameters in rat were measured and the results suggest that the body's exposure to active metabolites were much higher than to the prodrug with LOR, but much lower with DL. The tissue distribution study shows that LOR, DL and their active metabolites were widely distributed in the liver, spleen, thymus, heart, adrenal glands and pituitary gland. For immune-regulatory tissues, the concentrations of LOR, DL and their active metabolites in the spleen were much higher than in the thymus, which is related to the spleen, one of the sites where immune responses occur. LOR and its metabolites might inhibit immune-mediated allergic inflammation through the hypothalamic-pituitary-adrenal (HPA) axis. It was also found that the concentration of LOR in the heart was highest after liver and adrenal glands while those of DL, 6-OH-DL and 5-OH-DL in the liver, adrenal glands and spleen were all higher than those in the heart, which suggests that LOR may have a greater tendency to distribute in the heart than its metabolites.

Timing in drug absorption and disposition: The past, present, and future of chronopharmacokinetics

The importance of drug dosing time in pharmacokinetics, pharmacodynamics, and toxicity is receiving increasing attention from the scientific community. In spite of mounting evidence that circadian oscillations affect drug absorption, distribution, metabolism, and excretion (ADME), there remain many unanswered questions in this field and, occasionally, conflicting experimental results. Such data arise not only from translational difficulties caused by interspecies differences but also from variability in study design and a lack of understanding of how the circadian clock affects physiological factors that strongly influence ADME, namely, the expression and activity of drug transporters. Hence, the main goal of this review is to provide an updated analysis of the role of the circadian rhythm in drug absorption, distribution across blood-tissue barriers, metabolism in hepatic and extra-hepatic tissues, and hepatobiliary and renal excretion. It is expected that the research suggestions proposed here will contribute to a tissue-targeted and time-targeted pharmacotherapy.

Effect of taste masking technology on fast dissolving oral film: dissolution rate and bioavailability

Fast dissolving oral film is a stamp-style, drug-loaded polymer film with rapid disintegration and dissolution. This new kind of drug delivery system requires effective taste masking technology. Suspension intermediate and liposome intermediate were prepared, respectively, for the formulation of two kinds of fast dissolving oral films with the aim of studying the effect of taste masking technology on the bioavailability of oral films. Loratadine was selected as the model drug. The surface pH of the films was close to neutral, avoiding oral mucosal irritation or side effects. The thickness of a 2 cm × 2 cm suspension oral film containing 10 mg of loratadine was 100 μm. Electron microscope analysis showed that liposomes were spherical before and after re-dissolution, and drugs with obvious bitterness could be masked by the encapsulation of liposomes. Dissolution of the two films was superior to that of the commercial tablets. Rat pharmacokinetic experiments showed that the oral bioavailability of the suspension film was significantly higher than that of the commercial tablets, and the relative bioavailability of the suspension film was 175%. Liposomal film produced a certain amount of improvement in bioavailability, but lower than that of the suspension film.

Murine chronotoxicity to the antiallergic agent, cetirizine

Cetirizine is a second-generation histamine H1-receptor antagonist used in the treatment of allergic diseases. The aim of the study was to assess whether cetirizine toxicity estimated by, for example, death, body loss, and leucopenia, is circadian rhythm dependent. A total of 210 male Swiss mice, aged 9 weeks, were synchronized for 3 weeks to 12-hour light (i.e., rest span)/12-hour dark (i.e., activity span) cycles. The drug was administered per os (orally). Each lethal (DL(50) = 750 mg/kg) and sublethal (DT(50) = 55 mg/kg) dose was administered to comparable groups of animals at six different circadian time points (1, 5, 9, 13, 17, and 21 hours after light onset; HALO). The death rate was dosing time dependent (P <0.001). Drug dosing at 5 HALO resulted in maximum mortality (76.75%), whereas dosing at 17 HALO resulted in the lowest mortality rate (16.7%). Cosinor analyses validated a statistically significant circadian rhythm in death rate (P < 0.008). Changes in body weight after cetirizine administration were dosing time dependent (P < 0.01), with the dosing time of least effect (-0.7% loss) at 17 HALO and of greatest effect (-7% loss) at 5 HALO. Cosinor analyses validated a statistically significant circadian rhythm in body loss (P < 0.05). A statistically significant decrease in leukocyte number varied, according to antihistamine dosing time (P < 0.01), with the dosing time of least leucopenia (≈-17%) at 17 HALO and of greatest leucopenia (≈-28%) at 5 HALO. The results show that cetirizine dosing time at the midactivity (dark) span seems to be optimal, since it corresponds to the best tolerance.

Chronokinetics of ceftazidime after intramuscular administration to dogs

Ceftazidime, a third-generation cephalosporin, is widely used for the treatment of Pseudomonas aeruginosa infections. The aims of the present study were to characterize the pharmacokinetics of ceftazidime and to estimate the T > MIC against P. aeruginosa, after its intramuscular (i.m.) administration at two different dosing times (08:30 h and 20:30 h) to dogs, in order to determine whether time-of-day administration modifies ceftazidime pharmacokinetics and/or predicted clinical antipseudomonal efficacy. Six female healthy beagle dogs were administered ceftazidime pentahydrate by the intramuscular route in a single dose of 25 mg/kg at both 08:30 and 20:30 h, two weeks apart. Plasma ceftazidime concentrations were determined by microbiological assay. Pharmacokinetic parameters and time above the minimum inhibitory concentration (T > MIC) and 4xMIC for Pseudomonas aeruginosa were calculated from the disposition curve of each dog. No differences between the daytime and nighttime administrations were found for the main pharmacokinetic parameters, including C(max), t(max), t((1/2) lambda), AUC, and MRT; however, the high interindividual variability shown by these values and the small number of individuals may account for this lack of difference. Rate of absorption (k(a)) was significantly higher after the 20:30 h than 08:30 h administration. No significant differences between T > MIC were found when comparing the 08:30 h and 20:30 h administrations. Mean T > MIC values predicted a favorable bacteriostatic effect for all susceptible strains of P. aeruginosa for the 12 h dosing interval at both dosing times. Our results suggest that similar antipseudomonal activity may be expected when ceftazidime is administered at 8:30 and 20:30 h; however, as only two timepoints of drug administration were explored, we are unable to draw any conclusions for other treatment times during the 24 h.

Do restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS) play a role in nocturnal hypertension and increased cardiovascular risk of renally impaired patients?

Hypertension can cause or promote renal failure and is related to cardiovascular mortality, the major cause of death in patients with renal impairment. Changes in the circadian BP pattern, particularly the blunting or reversal of the nocturnal decline in BP, are common in chronic renal failure. These changes in turn are among the major determinants of left ventricular hypertrophy. Using a chronobiological approach, it is possible to obtain better insight into the reciprocal relationship between hypertension, renal disease, and increased cardiovascular risk of renal patients. Disruption of the normal circadian rhythm of rest/activity may be hypothesized to underlie the high cardiovascular morbidity and mortality of such patients. Epidemiological studies reveal that hemodialysis patients experience poor subjective sleep quality and insomnia and, in comparison to healthy persons, are more likely to show shorter sleep duration and lower sleep efficiency. Sleep apnea may be present and is usually investigated in these patients; however, the prevalence of restless legs syndrome (RLS), which is high in dialysis patients and which has been associated with increased risk for cardiovascular disease in the general population, could also play a role in the pathogenesis of sleep-time hypertension in renal patients. Careful assessment of sleep quality, in particular, diagnostic screening for RLS and periodic limb movements (PLM) in renal patients, is highly recommended. In renal failure, attention to sleep quality and related perturbations of the sleep/wake cycle may help prevent the occurrence and progression of cardiovascular disease.