Comparative Study of Psychomotor Performance Amongst Fixed Dose Combinations of First and Second Generation H1 Antihistaminics in Adult Healthy Volunteers

Background: Fixed dose combination (FDC) of first and second generation H₁ antihistaminics with paracetamol and phenylephrine are widely used and are the most frequent form of self-medication. Though previous studies have shown that H₁ antihistaminics cause psychomotor and cognitive impairment, to the best of our knowledge, no studies have utilized the FDC of antihistaminics to evaluate their effect on psychomotor performance. This study was planned to observe the effects of such combinations on CNS. The mainstay of the study was to compare the psychomotor perfor-mance upon administration of fixed dose combination of 1^st and 2^nd generation H₁ antihistaminics along with paracetamol and phenylephrine in adult healthy volunteers. Materials and Methods: This was double blind cross over study conducted in 12 adult healthy volunteers. Following single dose of FDC of the 1^st (chlorpheniramine maleate) and 2^nd (cetrizine) generation anti-histaminics with paracetamol and phenylephrine, volunteers were subjected to perform a battery of validated tests to evaluate their cognitive and psychomotor performance (simple reaction time, arithmetic ability test, digit substitution test, digit cancellation test, immediate and delayed recall rests and a Stanford drowsiness scale) 2 hrs post dose. Data was analysed using anal-ysis of variance test with Tukey's Multiple Comparison Test. A p value of < 0.05 was considered statistically significant. Results: FDC containing cetrizine did not show significant difference from the other FDC containing chlorpheniramine maleate in any of the tests which had been performed, except for a mildly sedative action of cetirizine containing FDC. Conclusion: FDC of antihistaminics do not cause impairment of cognition and psychomotor performance. Also, 2^nd generation antihistaminics are not free from adverse effect like sedation. The possible reasons behind the obtained results are addition of paracetamol and low doses of antihistaminics in FDCs, laxity of tests and single dose administration.