Methods

We performed a randomized, double-blinded, placebo-controlled, crossover study in young active duty personnel ( NCT01329679 ). BP assessment and an ECG evaluation were performed at baseline to exclude those with previously undiagnosed hypertension or rhythm disturbance. On enrollment, subjects were asked to drink either 5-Hour ENERGY or a placebo twice daily for 1 week (phase A), complete a 7-day washout period, and then crossover to the corresponding alternate study drink (phase B) ( Figure 1 ). Study drinks were consumed in the morning and afternoon (7:00 to 9:00 a.m . and 2:00 to 4:00 p.m .) consistently. BP and ECG evaluations were performed at baseline, 1, 3, and 5 hours on the first and seventh day in the morning during each phase (i.e., days 1, 7, 15, and 21).

Study schematic. Bl = baseline; BP = blood pressure; ECG = electrocardiogram.

Healthy volunteers between 18 and 40 years of age with no premorbid conditions were included. Subjects were excluded if having an initial elevated BP (≥140/80 mm Hg), a QTc interval >440 ms, or if they were on any medications known to interact with study drinks or affecting any hemodynamic or ECG parameters. Subjects were asked to abstain from all energy drinks for 1 week before randomization and during the study period. Caffeine consumption was not permitted beginning 48 hours before end point assessment days (days 1, 7, 15, and 21).

The regular strength 5-Hour ENERGY (2 fluid ounces), Lemon Lime flavor was used (5-Hour Energy; Living Essentials, LLC, Farmington Hills, Michigan). The placebo drink consisted of 24 ml of filtered water, 15 ml reconstituted lime juice, and 20 ml of cherry flavor syrup. Study drinks were prepared in identical looking bottles within 24 hours of administration. When not in the presence of a study team member, compliance to study drink consumption was documented by a self-reported log.

The specific end points evaluated were systolic and diastolic BPs, heart rate, PR interval, QRS duration, QT interval, and QTc interval. BPs were taken using a standard calibrated automated device (Masimo SET Vital Sign Monitor; Welch Allyn, Skaneateles Falls, New York) with the subject in the upright position, in duplicate, and averaged. A 12-lead electrocardiogram (PageWriter Trim III; Philips Healthcare, Andover, Massachusetts) was obtained with the patient in the supine position with the machine-reported ECG parameters used for data analysis. The machine corrected the QT interval (QTc) using the Bazzett’s formula. ECGs were recorded with 1 mV/cm standardization with a paper speed of 25 mm/s.

Based on estimates from previous studies, to detect a difference of 4 to 6 mm Hg (assuming a standard deviation of 8 mm Hg, alpha of 0.05, power of 80%) in systolic BP, a sample size of 16 to 34 subjects would be needed. A paired student’s t test was performed comparing the two arms at each time-point (time matched) along with descriptive reporting of data. All data are reported as mean ± SD. A p value ≤0.05 was considered statistically significant. Intention to treat analysis was performed and reported. The maximum post-dosing values were also compared.

Results

There were 26 subjects (20 men and 6 women) who completed the trial. The mean age and weight were 28 ± 6 years and 166 ± 31 pounds, respectively. Of the 26 subjects, 20 identified as white, 2 as black, 2 as Asian, and 2 as Hispanic. Of them, 21 subjects were caffeine users and 5 were caffeine abstainers.

Table 1 describes the hemodynamic and ECG effects after a single energy shot or placebo consumption. Post-dosing systolic BP was significantly elevated at 3 and 5 hours with energy drink consumption compared with placebo (p = 0.050 and p = 0.038, respectively). Post-dosing diastolic BP was significantly elevated at 1 and 5 hours with energy drink consumption (p = 0.019 and p = 0.043, respectively). Heart rate and ECG parameters were not significantly different.

Table 2 describes the hemodynamic and ECG effects after consuming an energy shot or placebo twice daily for 6 days (plus 1 shot on day 7). Systolic BP, diastolic BP, heart rate, and ECG parameters were not significantly different at any time-point.

Table 2

Hemodynamic and electrocardiographic changes post chronic consumption (day 7)

	Baseline	1-Hour	3-Hour	5-Hour	Maximum
	n = 26
Systolic BP (mmHg)
Placebo	120±9	120±8	120±9	120±9	124±8
Energy Drink	121±9	124±9	124±11	123±11	127±10
p-value	0.720	0.207	0.168	0.377	0.255
Diastolic BP (mmHg)
Placebo	76±6	77±7	76±7	75±6	79±6
Energy Drink	78±7	80±8	79±7	78±7	82±7
p-value	0.398	0.128	0.123	0.226	0.079
HR (bpm)
Placebo	61±8	63±7	60±7	63±7	67±8
Energy Drink	63±9	61±10	61±8	64±8	68±9
p-value	0.575	0.298	0.626	0.856	0.665
PR-Interval (msec)
Placebo	162±18	158±19	155±18	155±17	164±17
Energy Drink	159±17	158±15	154±19	156±18	164±15
p-value	0.571	0.865	0.784	0.820	0.989
QRS Duration (msec)
Placebo	91±10	90±10	90±10	91±10	93±9
Energy Drink	93±11	91±10	91±10	91±9	95±11
p-value	0.567	0.882	0.764	0.971	0.639
QT Interval (msec)
Placebo	411±22	403±22	408±22	402±22	418±21
Energy Drink	407±19	412±23	410±26	403±22	422±21
p-value	0.567	0.120	0.629	0.864	0.510
QTc Interval (msec)
Placebo	413±21	411±18	407±19	412±21	419±22
Energy Drink	413±23	411±25	413±24	414±21	426±20
p-value	0.895	0.961	0.229	0.772	0.257

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