Background: Cocaine lengthens electrocardiographic QTc, QRS and PR intervals through blockade of sodium and potassium channels, but changes during withdrawal have not been well studied.
Methods: 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.
Results: 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.
Conclusions: These findings suggest that cocaine-associated QTc prolongation returns toward normal during the first week of cocaine abstinence.