The effects on performance of cyclizine and pseudoephedrine during dry chamber dives breathing air to 30 metres' depth

McGeoch G, Davis FM, Fletcher L. The effects on performance of cyclizine and pseudoephedrine during dry chamber dives breathing air to 30 metres' depth. SPUMS J. 2005; 35: 178�82.) Twentyfour subjects ingested pseudoephedrine (60 mg), cyclizine (50 mg) or placebo approximately two hours before a dry chamber dive breathing air to five or 30 metres' seawater depth (msw; 151 or 404 kPa). Each subject did six dives, the sequence of drug ingestion and divedepth order assigned according to a counterbalanced design. Tests of grammatical reasoning, manual dexterity and simple arithmetic were performed. A small decrease in performance occurred at 30 msw in grammatical reasoning (P = 0.02) and manual dexterity (P = 0.02) irrespective of the drug taken. The type of drug affected grammatical reasoning performance (P = 0.002) such that performance impairment at depth for cyclizine was more than for pseudoephedrine (P = 0.007) or placebo (P = 0.002). The effect of drug on manual dexterity was not significant (P = 0.23). There were no depth or drug effects on the simple arithmetic test. There were no significant effects of drug order for either manual dexterity (P = 0.93) or grammatical reasoning (P = 0.10), but performance improved for both manual dexterity (P < 0.001) and grammatical reasoning (P < 0.001) over the dive series despite predive practice. Pseudoephedrine showed little or no effect on performance under these conditions, but the minor impairment with cyclizine suggests that it should be used with caution prior to air diving in open water conditions.