Torsades de pointes (TdP) is a potentially fatal ventricular arrhythmia associated with corrected QT (QTc) interval prolongation. More than 50 commonly used drugs available on the US market may cause QTc interval prolongation and TdP. While TdP occurs more commonly in women, 33-45% of all cases of TdP have occurred in men. Older age is a risk factor for drug-induced TdP in men, possibly due to declining serum testosterone concentrations. Available evidence shows an inverse relationship between QTc intervals and serum testosterone concentrations. In addition, experimental data, including those from the investigators' laboratory, suggest that both exogenous testosterone or progesterone administration may be protective against prolongation of ventricular repolarization and TdP. Specific Aim: Establish the influence of transdermal testosterone administration and oral progesterone administration as preventive methods by which to diminish the degree of drug-induced QT interval prolongation in men 65 years of age or older. Hypothesis: Transdermal testosterone administration and oral progesterone administration both effectively attenuate drug-induced QT interval response in older men. To test this hypothesis, transdermal testosterone, oral progesterone or placebo will be administered in a 3-way crossover study to men 65 years of age or older. QTc interval response to low-dose ibutilide will be assessed. The primary endpoints will be Fridericia-corrected QT interval (QTF) response to ibutilide, in the presence and absence of testosterone, and in the presence or absence of progesterone: 1) Effect on pre-ibutilide QTF, 2) Effect on maximum post-ibutilide QTF, 3) Effect on % change in post-ibutilide QTF, and 2) Area under the QTF interval-time curves.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
QUADRUPLE
Enrollment
14
Subjects will receive transdermal testosterone gel 1% 100 mg daily for 7 days
Subjects will receive oral progesterone 400 mg (two x 200 mg capsules) once daily every evening for 7 days
Subjects will receive placebo transdermal gel and placebo (lactose) capsules
Ibutilide 0.003 mg/kg administered to all subjects in all phases to moderately lengthen the QT interval
Indiana University
Indianapolis, Indiana, United States
Baseline (Pre-ibutilide) Individualized Rate-corrected QT Interval (QTF)
QT interval is an electrocardiogram (ECG) measure of ventricular repolarization. Prolonged QT interval is a marker of increased risk of the ventricular arrhythmia known as torsades de pointes, which can cause sudden cardiac death. QT intervals were measured from ECG lead II by one investigator (E.T.M.) who was blinded to the subjects' assigned treatment phases. QT intervals were measured using computerized high-resolution electronic calipers (EP Calipers 1.6). QT and RR intervals at each time point were averaged over 3 consecutive complexes. The end of the T-wave was determined via the tangent method. Only clearly discernable QT intervals were measured. QT intervals vary with heart rate, and therefore must be corrected for heart rate. QT intervals were corrected using the Fridericia (QTF) method. The baseline QTF assesses the influence of testosterone and progesterone on naturally-occurring (before ibutilide administration) QTF
Time frame: Following 7 days of testosterone, progesterone or placebo
Maximum QTF Following Ibutilide 0.003 mg/kg
QT interval is an ECG measure of ventricular repolarization. Prolonged QT interval is a marker of increased risk of the ventricular arrhythmia known as torsades de pointes, which can cause sudden cardiac death. Three 12-lead ECGs were obtained \~ 1 minute apart immediately at the end of the ibutilide infusion and at 5, 10, 15, 20, 30, and 45 minutes and 1, 2, 4, 6, and 8 hours post-infusion. QT intervals were measured from ECG lead II by one investigator (E.T.M.) who was blinded to the subjects' assigned treatment phases. QT intervals were measured using computerized high-resolution electronic calipers. QT and RR intervals at each time point were averaged over 3 consecutive complexes. The end of the T-wave was determined via the tangent method. QT intervals vary with heart rate, and therefore must be corrected for heart rate. QT intervals were corrected using the Fridericia (QTF) method. Maximum QTF is the longest QTF measured following ibutilide at any time point.
Time frame: Within 8 hours following ibutilide administration
Maximum Percent Change From Pretreatment Value in QTF Following Ibutilide 0.003 mg/kg
QT interval is an ECG measure of ventricular repolarization. Prolonged QT interval is a marker of increased risk of the ventricular arrhythmia known as torsades de pointes, which can cause sudden cardiac death. Three 12-lead ECGs were obtained \~ 1 minute apart immediately at the end of the ibutilide infusion and at 5, 10, 15, 20, 30, and 45 minutes and 1, 2, 4, 6, and 8 hours post-infusion. QT intervals were measured from ECG lead II by one investigator (E.T.M.) who was blinded to the subjects' assigned treatment phases. QT intervals were measured using computerized high-resolution electronic calipers. QT and RR intervals at each time point were averaged over 3 consecutive complexes. The end of the T-wave was determined via the tangent method. QT intervals were corrected using the Fridericia (QTF) method.
Time frame: Within 8 hours of ibutilide administration
Area Under the QTF Versus Time Curve for 0-1 Hour Following Ibutilide 0.003 mg/kg
Prolonged QT interval is a marker of increased risk of the ventricular arrhythmia known as torsades de pointes, which can cause sudden cardiac death. Three 12-lead ECGs were obtained \~ 1 minute apart immediately at the end of the ibutilide infusion and at 5, 10, 15, 20, 30, and 45 minutes and 1, 2, 4, 6, and 8 hours post-infusion. QT intervals were measured from ECG lead II by one investigator (E.T.M.) who was blinded to the subjects' assigned treatment phases. QT intervals were measured using computerized high-resolution electronic calipers. QT and RR intervals at each time point were averaged over 3 consecutive complexes. The end of the T-wave was determined via the tangent method. Area under the QTF curve was calculated using the trapezoidal rule and reflects overall QTF interval "exposure" over time.
Time frame: 1 hour following ibutilide administration
Number of Participants With Adverse Effects Associated With Testosterone, Progesterone and Placebo
Adverse effects were assessed by study investigators using telephone calls during the 7-day treatment period in each phase, as well as by asking participants about adverse effects on ibutilide administration days
Time frame: During 7 day administration periods
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