Efficacy and tolerability of astemizole-D and Loratadine-D during prolonged, controlled allergen challenge in the Vienna Challenge Chamber.

This randomized, double-blind, single-dummy, cross-over trial was initiated to compare the efficacy and tolerability of once-daily astemizole-D (CAS 141623-30-5; 10 mg astemizole/240 mg pseudoephedrine) with twice-daily loratadine D (CAS 132316-36-0; 5 mg loratadine/120 mg pseudoephedrine) during prolonged, controlled allergen challenge in the Vienna Challenge Chamber. Twelve atopic patients participated in this study with a treatment duration of 3 days. Pollen challenges were made on days 1 and 3: the first to assess onset of drug action; the second to determine duration of drug effect. Drug efficacy was assessed using a number of standard objective and subjective measures. Onset of action was found to be generally comparable in both treatment groups for all parameters tested with a mean overall onset of action of 65 min during treatment with astemizole-D compared with 70 min on loratadine-D. As expected, astemizole-D tended to have a longer duration of action, with symptom severity lower with this agent than with loratadine-D during the second challenge session despite the differences in dosing schedule. However, inter-group differences did not attain statistical significance. Patient evaluations of therapeutic efficacy confirm these findings. Both drugs were well-tolerated, although a non-significant trend towards greater sleep impairment was seen during treatment with loratadine-D. In conclusion, astemizole-D was shown to be at least as effective and well tolerated as loratadine-D for the treatment of allergen-induced rhinoconjunctivitis during prolonged, controlled allergen challenge.