Do pseudoephedrine or phenylpropanolamine improve maximum oxygen uptake and time to exhaustion?

OBJECTIVE

To study the effects of over-the-counter dosages of the pure alpha 1-agonists pseudoephedrine (PSE) and phenylpropanolamine (PPA) on selected parameters of exercise performance, and to establish a range of corresponding drug levels in the urine of the athletes who use these drugs.

DESIGN

Placebo-controlled, randomized, double-blinded, multiple-dose trial.

SETTING

The National Institute of Fitness and Sport, the Department of Family Medicine, Indiana University, and the Sports Medicine Lab, Department of Pathology, Indiana University, Indianapolis, Indiana.

PARTICIPANTS

A convenience sample of 20 male cyclists, aged 18-35, from the local cycling community. Inclusion criteria required cycling at least 50 miles a week, no chronic medical problems, and not taking any medications. Subjects were recruited by local ads and word of mouth.

INTERVENTION

Patients were randomized to one of two groups of 10 subjects. Each subject in both groups performed three separate bicycle ergometer tests after ingestion of varying dosages of alpha 1-agonists. One group performed tests after receiving placebo, 0.33 mg/kg PPA, and 0.66 mg/kg PPA, whereas the other group received placebo, 1 mg/kg PSE, and 2 mg/kg PSE. A minimum 1-week washout period was required between tests. Urine for drug testing was collected 1 h before, immediately afterward, and the next morning after testing. Drug testing was performed by gas GC/MCD at a facility approved by the International Olympic Committee.

MAIN OUTCOME MEASURES

Maximum oxygen uptake (VO2max), time to exhaustion, urine drug levels of PSE and PPA, peak blood pressures (BPs), peak pulse, and Borg scale (rating of perceived exertion or RPE).

MAIN RESULTS

In the PPA group, the 0.33-mg/kg dose resulted in insignificant changes in peak systolic BP (+5.4 mm Hg, p = 0.260), peak diastolic BP (-1.6 mm Hg, p = 0.622), peak pulse (-2.2 beats/min, p = 0.12), peak Borg (RPE = -0.10 (p = 0.823), time to exhaustion (-16.9 s, p = 0.287), and VO2max (+0.50 ml/kg/min, p = 0.71). No significant change was noted in any study variable at the 0.66-mg/kg PPA dose, and some effects were dissimilar to the lower PPA dose effects. Peak systolic BP increased 2.8 mm Hg (p = 0.617), diastolic BP decreased 1.6 mm Hg (p = 0.634), peak pulse increased 1.4 beats/min (p = 0.504), peak Borg RPE decreased 0.80 (p = 0.210), time to exhaustion decreased 2.6 s (p = 0.861), and VO2max decreased 2.92 ml/kg/min (p = 0.14). In the 1-mg/kg PSE group, there was a significant increase in peak systolic BP (+10.6 mm Hg, p = 0.029). No significant changes occurred in peak diastolic BP (+2.4 mm Hg, p = 0.333), peak pulse (+2.2 beats/min, p = 0.306), peak RPE (+0.2, p = 0.62), time to exhaustion (+21.4 s, p = 0.289), and VO2max (+2.29 ml/kg/min, p = 0.31). In the 2-mg/kg PSE dose trial, there were insignificant changes in peak systolic BP of +2.4 mm Hg (p = 0.559), +3.8 mm Hg in peak diastolic BP (p = 0.106), +1.6 beats/min in peak pulse (p = 0.586), -0.1 in peak Borg RPE scales (p = 0.76), -10.4 s in time to exhaustion (p = 0.41), and +1.79 ml/kg/min in VO2max (p = 0.43). Urine drug levels in those subjects receiving 1 mg/kg PSE ranged from 7-55 micrograms/ml before performance and 30-128 micrograms/ ml after performance to 7-35 micrograms/ml the next morning. Levels in those receiving 2 mg/kg ranged from 5-160 micrograms/ml before performance and 44-200 micrograms/ml after performance to 8-44 micrograms/ ml the next day. In the PPA 0.33-mg/kg dose trials, the levels ranged 1-36 micrograms/ml before performance and 9-50 micrograms/ml after performance to < 1-14 micrograms/ml the next morning. In the PPA 0.66-mg/kg dose trials, the levels were 4-52 micrograms/ml before performance, 8-80 micrograms/ml after performance, and 6-74 micrograms/ml the next day.

CONCLUSIONS

We found no significant differences between trials in maximum oxygen uptake (VO2max), peak or progression of Borg Scale (RPE), maximum systolic and diastolic BPs, peak pulse, or t