Antihistamines levocetirizine

The second generation H -receptor antagonist cetirizine is a reacemate consisting of equal quantities of 2 enantiomers, levocetirizine [(R)-enantiomer] and dextrocetirizine [(S)-enantiomer]. In vitro and human pharmacodynamic studies have provided evidence that levocetirizine is the more active enantiomer, accounting for most or all clinical antihistaminic activity of racemic cetirizine this activity of levocetirizine is seen at half the dose of cetirizine. 

The effect of levocetirizine 5 mg/day on actual driving performance during normal traffic has been compared with the effect of the first-generation antihistamine diphenhydramine 50 mg/day in 48 healthy volunteers in a double-blind, placebo-controlled, randomized trial (73). Treatments were given on days 1, 2, 3, and 4, at 90 minutes before the start of a standardized driving test on days 1 and 4. In contrast to diphenhydramine, driving performance was not significantly affected by levocetirizine 5 mg/day. 

Gandon JM, Allain H. Lack of effect of single and repeated doses of levocetirizine, a new antihistamine drug, on cognitive and psychomotor functions in healthy volunteers. Br J din Pharmacol 2002 54(l) 51-8. 

BARBITURATES SODIUM OXYBATE Risk of CNS depression - coma, respiratory depression Additive depression of CNS Avoid co-administration. Caution even with relatively non-sedating antihistamines (cetrizine, desloratidine, fexofenadine, levocetirizine, loratidine, mizolastine) as they can impair performance of skilled tasks... 

Cetirizine, the acid metabolite from oxidation of the primary alcohol of the antihistamine hydroxyzine (Fig. 37.15 and Table 37.6), is a widely used antihistamine (38). It has a long duration of action and is highly selective for Hi receptors. No cardiotoxicity has been reported, but some drowsiness occurs. The R-enantiomer of cetirizine, levocetirizine, is marketed in Europe. Levocetirizine has higher affinity than its S-enantiomer for the Hi receptor (>30-fold) and is more slowly dissociated by more than 20-fold from the receptor (39). Thus, the antihistaminic... 

The non-sedating antihistamines seem to cause little or no drowsiness in most patients and the risks if taken alone or with alcohol appear to be minimal or absent. However, the incidence of sedation varies with the non-sedating antihistamine (e.g. sedation appears to be lower with fexofenadine and loratadine than with acrivastine or cetirizine) and with the individual (e.g. women may be more affected than men). Therefore, patients should be advised to be alert to the possibility of drowsiness if they have not taken the drug before. Any drowsiness would be apparent after the first few doses. The patient information leaflets for acrivastine and cetirizine suggest avoidance of alcohol or excessive amounts of alcohol, and caution is advised with levocetirizine. ... 

Fexofenadine levels are raised by both azithromycin and erythromycin but because this does not result in adverse cardiac effects concurrent use is considered safe. Azelastine, cetirizine (and therefore probably its isomer levocetirizine) desloratadine and levocabastine seem to be free from clinically significant pharmacokinetic interactions, and have no cardiac effects, and so may therefore provide suitable alternatives if a non-sedating antihistamine is needed in a patient taking macrolides. 

Comparative studies European guidelines have recommended increased antihistamine doses of up to fourfold in patients with resistant urticaria [25 ], a recommendation that has been supported by a dose-escalation study that compared levocetirizine and desloratadine in such patients [26 ]. The effects of rupatadine at four times the recommended dose (40 mg) on platelet-activating factor (PAF) and histamine-induced cutaneous wheal and flare responses have been assessed in six healthy men [27. Rupatadine suppressed wheal and flare responses induced by both mediators for up to 72 hours after dosing. All of the subjects reported mild somnolence within 1-3 hours of taking rupatadine. 

This was her first exposure to cetirizine or any other piperazine derivative, and on recovery she reported no previous history of allergic drug reactions or concomitant use of any other medication or alcohol [3 ]. Although fixed drug eruptions have been previously reported with both cetirizine and levocetirizine [SEDA-31, 30] anaphylaxis caused by systemic antihistamines is very rare, particularly in the absence of known previous exposure. The authors speculated that the potential antigenic nature of the piperazine ring may have been a factor [4 ]. 

---