Longitudinal ECG changes in cocaine users during extended abstinence.

Abstract

Cocaine lengthens electrocardiographic QTc, QRS and PR intervals through blockade of sodium and potassium channels, but changes during withdrawal have not been well studied. We recorded weekly electrocardiograms (ECGs) from 25 physically healthy cocaine users (84.0% men, mean [S.D.] age 34.7 [4.1] years, 9.0 [5.2] years of cocaine use, 9.4 [3.5] days of use in the 2 weeks prior to admission) over 3 months of monitored abstinence on a closed ward. Subjects had minimal current use of other drugs. Baseline ECGs were recorded 20.5 h [16.6] after last cocaine use. Baseline QTc interval correlated positively with total amount of cocaine used and amount used per day in the 2 weeks prior to ward admission. There was a significant 10.5 ms [12.9] shortening of QTc interval during the first week of withdrawal, with no further significant changes thereafter. There were no significant changes in PR or QRS intervals. These findings suggest that cocaine-associated QTc prolongation returns toward normal during the first week of cocaine abstinence.