Ultrasound assisted enzyme catalyzed degradation of Cetirizine dihydrochloride

Cetirizine dihydrochloride, a pharmaceutical drug of the class antihistamines is frequently detected in wastewater samples. In the present work, the degradation of Cetirizine dihydrochloride is carried out using a novel technique of laccase enzyme as a catalyst under the influence of ultrasound irradiation. Effect of various process parameters such as enzyme loading, temperature, power, duty cycle, frequency and speed of agitation has been studied along with identification of the degradation intermediates. The maximum degradation of 91% is achieved at optimized experimental parameters such as 0.02% enzyme loading (w/v), 50°C temperature, power input of 100 W, 25 kHz frequency and 50% duty cycle with agitation speed of 200 rpm. It is observed that enzymatic degradation of Cetirizine dihydrochloride under the influence of ultrasound irradiation not only enhances the degradation but also reduces the time of degradation as compared to conventional enzymatic degradation technique.

Study on the interaction of levocetirizine dihydrochloride with human serum albumin by molecular spectroscopy

The interaction between cetirizine dihydrochloride and human serum albumin (HSA) has been examined by the spectroscopic techniques first. According to Stern-Volmer equation at different temperatures and the UV-vis spectra examination it was demonstrated that HSA fluorescence quenching initiated by levocetirizine was static. The values of binding constant (K(A)) and the number of binding sites (n) for levocetirizine and HSA were smaller than those for cetirizine and HSA, which meant that the transport of drug was regulated by the stereoselectivity of HSA to the enantiomer. The effect of the non-enzymatic glycosylation (NEG) on the interaction between levocetirizine and HSA signified that the administration of levocetirizine for diabetes should be different from the normal. The positive DeltaS(o) and negative DeltaH(o) indicated that ionic interaction played a major role between levocetirizine and HSA. Circular dichroism (CD) measurement showed that the secondary structure of HSA has changed in the presence of levocetirizine, and alpha-helical content decreased from 63.1% for free HSA to 54.9% for combined HSA, and accordingly the other secondary structure (beta-strand, beta-turns and others) contents increased to some extent. Finally, by the competitive binding experiments it was deduced that levocetirizine specifically bound to HSA in the region of site II, which meant the curative effect of levocetirizine should be reconsidered when it was administrated together with other site II drugs.

Population pharmacokinetics of levocetirizine in very young children: the pediatricians' perspective

Developmental changes during infancy and childhood can affect drug pharmacokinetics (PK), i.e., absorption, distribution, metabolism, and renal excretion. This, in turn, influences optimal dosing, efficacy, and safety. To date, of the 40 H1-antihistamines available worldwide, only 11 have been studied in children using a PK approach. Here, we provide the pediatricians' perspective on the population PK of levocetirizine, the pharmacologically active enantiomer of cetirizine, in very young children who received oral cetirizine, and describe the factors that influence levocetirizine PK in this population. In a prospective, randomized, double-blind, parallel-group, placebo-controlled study, very young children received oral cetirizine 0.25 mg/kg twice daily for 18 months. Plasma levocetirizine concentrations were measured in timed, sparse blood samples collected at steady-state (3, 12 and 18 months after commencement of treatment) for the purpose of monitoring safety, and levocetirizine population, PK parameters were derived by using non-linear mixed effects modeling. In 343 children (age 14-46 months, body weight 8.2-20.5 kg), a total of 943 blood samples were obtained. Compliance with cetirizine dosing was documented. The population PK model used predicted that with increasing body weight, levocetirizine oral clearance would increase by 0.044 l/h/kg, and levocetirizine volume of distribution would increase by 0.639 l/kg. Levocetirizine PK were not influenced by eosinophilia, sensitization to allergens, allergic disease, gastroenteritis/diarrhea, or concomitant ingestion of other medications. This population PK model predicts that in very young children, the oral clearance of levocetirizine will be rapid and will increase as body weight and age increase, therefore, levocetirizine dosing should be based on body weight and age in this population. Compared with older patients, on a mg/kg basis, relatively higher doses may be needed, and twice-daily dosing may be necessary, as previously reported for the related racemic H1-antihistamine cetirizine.

Comparison of pharmacokinetics and metabolism of desloratadine, fexofenadine, levocetirizine and mizolastine in humans

Abstract Absorption, distribution, metabolism and excretion of desloratadine, fexofenadine, levocetirizine, and mizolastine in humans have been compared. The time required to reach peak plasma levels (tmax) is shortest for levocetirizine (0.9 h) and longest for desloratadine (> or =3 h). Steady-state plasma levels are attained after about 6 days for desloratadine, 3 days for fexofenadine, 2-3 days for mizolastine and by the second day for levocetirizine. The apparent volume of distribution is limited for levocetirizine (0.4 L/kg) and mizolastine (1-1.2 L/kg), larger for fexofenadine (5.4-5.8 L/kg) and particularly large for desloratadine (approximately 49 l/kg). Fexofenadine and levocetirizine appear to be very poorly metabolized (approximately 5 and 14% of the total oral dose, respectively). Desloratadine and mizolastine are extensively metabolized. After administration of 14C-levocetirizine to healthy volunteers, 85 and 13% of the radioactivity are recovered in urine and faeces, respectively. In contrast, faeces are the preferential route of excretion for 14C-fexofenadine (80% vs. 11% of the radioactive dose in urine). The corresponding values are 41% (urine) and 47% (faeces) for 14C-desloratadine, 84-95% (faeces) and 8-15% (urine) for 14C-mizolastine. The absolute bioavailability is 50-65% for mizolastine; it is high for levocetirizine as the percentage of the drug eliminated unchanged in the 48 h urine is 77% of the oral dose; the estimation for fexofenadine is at least 33%; no estimation was found for desloratadine. Fexofenadine is a P-glycoprotein (P-gp) substrate and P-gp is certainly involved both in the poor brain penetration by the compound and, at least partially, in a number of observed drug interactions. An interaction of desloratadine with P-gp has been suggested in mice, whereas the information on mizolastine is very poor. The fact that levocetirizine is a substrate of P-gp, although weak in an in vitro model, could contribute to prevent drug penetration into the brain, whereas it is unlikely to be of any clinical relevance for P-gp-mediated drug interactions.

Therapeutic index of H1-antihistamines: example of cetirizine

BACKGROUND

The second generation H1 antihistamines were considered to have an improved risk/benefit ratio because of their low penetration into the brain and their very low incidence of CNS depressant effects. Nevertheless, the cardiac rhythm disturbances described under terfenadine and astemizole intake drew the attention to the fact that the low penetration into the brain is only one limited item in the evaluation of their respective therapeutic indices. A correct evaluation of the therapeutic index should always comprise a large series of items: all desired and not desired effects and properties should be considered together with the physicobiochemical mechanisms of the drugs at cell and membrane levels.

Molecular properties and pharmacokinetic behavior of cetirizine, a zwitterionic H1-receptor antagonist

The ionization and lipophilicity behavior of the antihistamine (H1-receptor antagonist) cetirizine was investigated, showing the drug to exist almost exclusively as a zwitterion in the pH region 3.5-7.5. In this pH range, its octanol/water lipophilicity is constant and low compared to cationic antihistamines (log D = log PZ = 1.5), whereas its H-bonding capacity is relatively large (delta log PZ > or = 3.1). Conformational, electronic, and lipophilicity potential calculations revealed that zwitterionic cetirizine experiences partial intramolecular charge neutralization in folded conformers of lower polarity. Pharmacokinetic investigations have shown the drug to be highly bound to blood proteins, mainly serum albumin, and to have a low brain uptake, explaining its lack of sedative effects. As such, cetirizine does not differ from "second-generation" antihistamines. In contrast, its very low apparent volume of distribution in humans (0.4 L kg-1, smaller than that of exchangeable water) implies a low affinity for lean tissues such as the myocardium and is compatible with the absence of cardiotoxicity of the drug. The zwitterionic nature and modest lipophilicity of cetirizine may account for this pharmacokinetic behavior. The suggestion is offered that cetirizine and analogous zwitterions, whose physicochemical, pharmacokinetic, and pharmacodynamic properties differ from those of "first-" and "second-generation" drugs in this class, could be considered as "third-generation" antihistamines.