Serum caffeine levels after 24-hour abstention: clinical implications on dipyridamole (201)Tl myocardial perfusion imaging.
BACKGROUND
Caffeine binds to the A2 receptors and inhibits adenosine's action of vasodilation or dipyridamole-induced vasodilation. Patients scheduled for (201)Tl myocardial perfusion using pharmacologic stress with dipyridamole or adenosine are advised to abstain from caffeine for 24 h before the test. This article reports on the residual serum caffeine levels of 36 patients after 24-h caffeine abstention and the clinical implications on dipyridamole (201)Tl myocardial perfusion imaging.


RESULTS
Heart rate, diastolic blood pressure, and systolic blood pressure were recorded before and after dipyridamole infusion. Sixty-six percent of the patients had detectable plasma caffeine but all values were within the range of 0.1-0.8 mg/L. No statistically significant change in diastolic and systolic blood pressures after dipyridamole infusion has been observed. The mean heart rate was increased by 18% after dipyridamole infusion in patients with zero caffeine, and the heart rate increase was inversely correlated with the serum caffeine levels (r = -0.22) with 81% confidence.


CONCLUSIONS
A serum caffeine level of 2 mg/L is predicted to be the lower limit for false-negative dipyridamole (201)Tl myocardial perfusion. The increase of heart rate after dipyridamole infusion could be the simple indicator for the serum caffeine level. Rescheduling of the patient study or further adenosine challenge is necessary only if the heart rate increase is <5% after dipyridamole or adenosine infusion.
School of Clinical Sciences, Faculty of Health Studies, Charles Sturt University, Wagga Wagga, New South Wales, Australia. xzheng@csu.edu.au
Xiao Ming
XM
Zheng
Robert Charles
RC
Williams
D000368:Aged; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002110:Caffeine / Q000008:administration & dosage / Q000097:blood*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000097:blood; D004176:Dipyridamole / Q000008:administration & dosage; D005080:Exercise Test / Q000379:methods; D005188:False Negative Reactions; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013793:Thallium / Q000008:administration & dosage; D014665:Vasodilator Agents / Q000008:administration & dosage
D000697:Central Nervous System Stimulants; D014665:Vasodilator Agents; C027549:thallium chloride; D002110:Caffeine; D004176:Dipyridamole; D013793:Thallium