triprolidine and mizolastine

Most of the modern non-sedating H1 receptor antagonists (antihistamines) penetrate the brain poorly, allowing the use of doses large enough to counteract allergic processes in peripheral tissues without important central effects. The antihistamines reviewed here are acrivastine, astemizole, cetirizine, ebastine, fexofenadine, loratadine, mizolastine, and terfenadine. However, these drugs are not entirely free from central effects, and there are at least quantitative differences between them. Although psychomotor and sleep studies in healthy subjects in the laboratory may predict that an antihistamine does not cause drowsiness, the safety margin can be narrow enough to cause a central sedating effect during actual treatment. This might result from a patient's individual sensitivity, disease-induced sedation, or drug dosages that are for various reasons relatively or absolutely larger (patient's weight, poor response, reduced drug clearance, interactions). Mild to even moderate sedation is not necessarily a major nuisance, particularly if stimulants need be added to the regimen (e.g. in perennial rhinitis). Furthermore, patients can adjust doses themselves if needed. Sedating antihistamines are not needed for long-term itching, because glucocorticoids are indicated and more effective. It is wise to restrict or avoid using antihistamines (astemizole, terfenadine) that can cause cardiac dysrhythmias, because even severe cardiotoxicity can occur in certain pharmacokinetic drug-drug interactions. Histamine H1 receptor antagonists (antihistamines) are used in the treatment of allergic disorders. The therapeutic effects of most of the older antihistamines were associated with sedating effects on the central nervous system (CNS) and antimuscarinic effects causing dry mouth and blurred vision. Non-specific "quinidine-like" or local anaesthetic actions often led to cardiotoxicity in animals and man. Although such adverse effects varied from drug to drug, there was some degree of sedation with all old antihistamines. Non-sedating antihistamines have become available during the past 15 years. Some of them also have antiserotonin or other actions that oppose allergic inflammation, and they are not entirely free from sedative effects either. In small to moderate "clinical" concentrations they are competitive H1 receptor antagonists, although large concentrations of some of them exert non-competitive blockade. Daytime drowsiness and weakness are seldom really important,

Topics: Astemizole; Benzimidazoles; Butyrophenones; Central Nervous System; Cetirizine; Drug Interactions; Heart; Histamine H1 Antagonists; Humans; Hypnotics and Sedatives; Loratadine; Piperidines; Potassium Channel Blockers; Terfenadine; Triprolidine

The review summarizes the major results of eight double-blind, placebo-controlled, volunteer studies undertaken by three independent institutions for showing the effects on actual driving performance of "sedating" and "nonsedating" antihistamines (respectively, triprolidine, diphenhydramine, clemastine and terfenadine, loratadine, cetirizine, acrivastine, mizolastine, and ebastine). A common, standardized test was used that measures driving impairment from vehicular "weaving" (i.e., standard deviation of lateral position (SDLP)). Logical relationships were found between impairment and dose, time after dosing, and repeated doses over 4-5 days. The newer drugs were generally less impairing, but differences existed among their effects, and none was unimpairing at doses 1-2x the currently recommended levels. One or possibly two of the newer drugs possessed both performance-enhancing and -impairing properties, depending on dose, suggesting two mechanisms of action.

Topics: Automobile Driving; Benzimidazoles; Butyrophenones; Cetirizine; Clemastine; Diphenhydramine; Dose-Response Relationship, Drug; Histamine H1 Antagonists; Humans; Loratadine; Netherlands; Piperidines; Psychomotor Performance; Terfenadine; Triprolidine

Eighteen healthy volunteers received mizolastine 5 mg, 15 mg or 45 mg, terfenadine 60 mg, triprolidine 10 mg or placebo in a 6-way crossover, double blind study. Following each dose, subjects performed a series of tests of cognitive function and psychomotor performance at 1, 3, 5, 8 and 24 hours post-dose. The test battery included critical flicker fusion, choice reaction time, tracking, Stroop and Sternberg memory tests and assessment of subjective sedation. Sedative effects and a concomitant reduction in psychomotor and cognitive function were observed following triprolidine, terfenadine and the highest dose of mizolastine, 45 mg, e.g. triprolidine reduced CFF threshold by 1.5 Hz and increased reaction time by 50 ms, impairments comparable to those caused by blood alcohol concentrations of 50 mg%, the legal limit in many countries. Mizolastine 5 mg did not differ significantly from placebo and at 15 mg differed only at one test point at one time. It may be concluded that mizolastine (5 mg and 15 mg) is free from disruptive effects on cognitive function and psychomotor performance, in contrast to terfenadine 60 mg, triprolidine 10 mg and mizolastine 45 mg.

Topics: Adolescent; Adult; Benzimidazoles; Cognition; Histamine H1 Antagonists; Humans; Male; Memory; Placebos; Psychomotor Performance; Terfenadine; Triprolidine