Mizolastine

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Abstract
Mizolastine is a second generation antihistamine agent with high affinity and specificity for histamine H1 receptors. Mizolastine has demonstrated antiallergic effects in animals and healthy volunteers and anti-inflammatory activity in animal models. Double-blind trials have shown mizolastine to be significantly more effective than placebo and as effective as other second generation antihistamine agents, such as loratadine or cetirizine, in the management of patients with perennial or seasonal allergic rhinitis and in patients with chronic idiopathic urticaria. Available data also suggest that prophylactic administration of mizolastine is significantly more effective than placebo and as effective as prophylactic terfenadine in delaying the onset of symptoms of seasonal allergic rhinitis. Mizolastine 10 mg/day is generally well tolerated, with the most common adverse events being drowsiness (7%), fatigue (2%), increased appetite (2%) and dry mouth (2%). In volunteers and patients the incidence of prolonged QTC interval was similar in mizolastine and placebo recipients, although mizolastine is contraindicated in those with cardiac disease or hepatic impairment or in those receiving erythromycin, ketoconazole or class I or III antiarrhythmic agents. Tests of psychomotor function in volunteers revealed no impairment after single doses of mizolastine ≤10mg. Conclusions: Mizolastine is a second generation antihistamine agent administered at a dosage of 10mg once daily. Unlike terfenadine and astemizole, mizolastine has not been shown to increase the QTC interval in volunteers and patients. Mizolastine may be considered an effective alternative to other second generation antihistamine agents in the management of allergic rhinitis and chronic idiopathic urticaria. In vitro studies have shown mizolastine to be a specific histamine H1 receptor antagonist. Mizolastine was 10- to 21-fold more potent than terfenadine, cetirizine and loratadine in displacing [3 H]pyrilamine from H1 receptors in guinea-pig cerebellar tissues. The antihistamine activity of mizolastine is similar to that of cetirizine and 7-fold more potent than that of loratadine in animal studies. In experimental models, oral mizolastine, but not oral terfenadine, loratadine or pyrilamine, showed anti-inflammatory activity at a dose of 0.1 to 10 mg/kg; this effect was not H1 receptor-mediated but may have been attributable to inhibition of 5-lipoxygenase. In volunteers, maximal inhibition of wheal and flare responses to intradermal histamine was achieved with mizolastine 10 and 20mg, respectively. The inhibition of wheal and flare responses with mizolastine 10mg was significantly greater than that in placebo recipients after 1 hour and 30 to 35% inhibition of the flare response was observed after 24 hours. No tolerance developed to the antihistamine activity of mizolastine over 8 weeks. In pollen-sensitive patients, mizolastine inhibited early and late soluble intercellular adhesion molecule-1 release and protein extravasation at challenged skin sites. However, some antiallergic effects of mizolastine observed in animal models, such as inhibition of histamine release from mast cells and inhibition of cell migration, were not observed in allergic patients. In single doses of up to 10mg, mizolastine did not cause any sedative effect, as assessed by performance in standard tests of psychomotor function and simulated and actual car driving tests, in healthy volunteers. The effects of mizolastine in these tests were generally similar to those of cetirizine 10mg or placebo. The effects of mizolastine, in repeated doses of up to 40 mg/day for 7 days, on the QTc interval in ECG recordings were similar to those of placebo in healthy volunteers. Concurrent administration of diltiazem or erythromycin with mizolastine did not prolong the QTC interval compared with placebo. Mizolastine is administered orally and has a bioavailability of 65.5%. A peak plasma mizolastine concentration (Cmax) of 0.3 mg/L is achieved in 1.5 hours after mizolastine 10mg. Mizolastine has a distribution half-life of 1.9 hours and is highly plasma protein bound (>98%). The apparent volume of distribution of mizolastine is 1.4 L/kg. Most of the drug is metabolised in the liver and only a small fraction (max, a lower Cmax, a prolonged distribution half-life and an increased area under the plasma concentration-time curve compared with healthy volunteers. No clinically relevant interactions were found between mizolastine and digoxin, diltiazem, theophylline, ethanol or lorazepam in healthy volunteers, although plasma concentrations of digoxin and theophylline were increased. The beneficial effects of mizolastine 10 mg/day on symptoms of seasonal allergic rhinitis were observed within 2 hours after oral administration. The efficacy of mizolastine 10 mg/day was greater than that of placebo and similar to that of cetirizine 10 mg/day in large double-blind trials in patients with seasonal allergic rhinitis. Prophylactic administration of mizolastine 10 mg/day was as effective as terfenadine 120 mg/day in delaying the onset of seasonal allergic rhinitis. Mizolastine 10 mg/day was significantly more effective than placebo and loratadine 10 mg/day in double-blind trials in patients with perennial allergic rhinitis. After 4 weeks, the effects of mizolastine 15 mg/day were similar to those of dexclorpheniramine 12 mg/day. Patients receiving mizolastine 10 mg/day showed significant improvement in nasal obstruction after 4 weeks compared with those receiving placebo. The symptomatic benefit with mizolastine 10 to 15 mg/day was sustained over 6 months in a nonblind trial in 141 patients with perennial allergic rhinitis after a 1-month double-blind, placebo-controlled phase. In patients with chronic idiopathic urticaria, the decrease in symptom severity and frequency with mizolastine 10 mg/day was similar to that observed with loratadine 10 mg/day or cetirizine 10 mg/day and significantly better than that of placebo in double-blind trials. The majority of patients with chronic urticaria showed a sustained symptomatic benefit with mizolastine 10 to 15 mg/day over 12 months. Adverse events occurred in 22% of patients receiving mizolastine 10 mg/day, but only 1% of patients discontinued the drug because of adverse events. The most common adverse events encountered with mizolastine 10 mg/day were drowsiness (7%), fatigue (2%), increased appetite (2%), dry mouth (2%), abdominal pain (1%), vertigo (1%) and headache (1%) in 130 patients with seasonal allergic rhinitis. No potentiation of the CNS depressant effects of ethanol or lorazepam occurred with the concurrent administration of mizolastine 10mg in healthy volunteers. The effects of mizolastine 10 mg/day on the QTC interval in patients with chronic idiopathic urticaria or allergy to grass pollen or house dust mites were similar to those of loratadine 10 mg/day or of placebo. Mizolastine is recommended at a dosage of 10mg administered once daily, for use in adults and children ≥12 years of age with seasonal or perennial allergic rhinitis or chronic idiopathic urticaria. No dosage adjustment is required in the elderly or in those with renal impairment. The use of mizolastine is contraindicated in patients with hepatic impairment and in those with clinically significant cardiac disease. Mizolastine should not be used in patients already receiving erythromycin, ketoconazole or class I or III antiarrhythmic agents.

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