The effect of captopril on +Gz tolerance of normotensives

Recently, there has been considerable interest in whether angiotensin converting enzyme inhibitors can be used to treat hypertensive pilots without compromising their operational effectiveness. This study was undertaken to evaluate the possible effects of captopril on tolerance to +Gz, of relevance in tactical fighter operations. A counterbalanced double blind crossover protocol was used to administer 25 mg of captopril or placebo twice daily in identical capsules to seven fit, normotensive individuals from the DCIEM acceleration research panel. The five males and two females took each course of capsules for 4 d prior to G-tolerance assessment and waited 1 week for drug wash-out after assessment on their first condition prior to commencement of the second course of capsules. The subjects did not wear G-suits. Standard ASCC gradual onset runs, relaxed and with a straining maneuver, and rapid onset runs were used to assess G tolerance. The group G tolerances are listed as mean +/- S.E.M.: during relaxed gradual onset runs (GOR) 3.96 +/- 0.14 on placebo and 3.61 +/- 0.10 on captopril (p = 0.02, paired t-test). Corresponding results for relaxed rapid onset runs (ROR) were 3.36 +/- 0.17 on placebo and 3.33 +/- 0.18 on captopril (p = 0.21, Wilcoxon signed ranks test). The straining tolerances during GOR runs were 7.21 +/- 0.23 on placebo and 6.83 +/- 0.25 while on captopril (p = 0.05, paired t-test). Given the relatively low dosage and the significant compromise of Gz-tolerance on both relaxed and straining GOR runs, caution is recommended in using captopril to treat hypertensive fighter aircrew.(ABSTRACT TRUNCATED AT 250 WORDS)