Theophylline decreases pain in the ischaemic forearm test.
To study the hypothesis that endogenous adenosine is a mediator of the ischaemic pain sensation, the effect of the adenosine receptor blocker theophylline (5.5 mg of the ethylendiamine salt.kg-1 intravenously) was tested in a placebo controlled double blind cross over study (placebo/theophylline/placebo or placebo/placebo/theophylline) in five healthy volunteers. Ischaemic work was performed with a spring loaded hand ergometer (1 Hz). The pain sensation was continuously reported using the Borg scale. Blood flow was measured by occlusion plethysmography. Pain was reported 18 (SEM 2.4) s after starting the ischaemic work and increased continuously to a maximum after 129(18) s (placebo). Theophylline at a plasma concentration of 75(7) mumol.litre-1 decreased the pain sensation in relation to working time. With theophylline, 12(3)% more work (p less than 0.01) was performed for the same reported pain estimate. Blood flow increased from a basal level of 52(9) to 495(55) ml.min-1.100 ml-1 30 s after work and returned to normal within 30-40 min. Theophylline did not affect blood flow. In conclusion, theophylline has a small but significant inhibitory effect on the ischaemic pain sensation compatible with a hyperalgesic effect of adenosine.
Jonzon
B
B
Department of Clinical Pharmacology and Internal Medicine, Huddinge Hospital, Sweden.
Sylvén
C
C
Kaijser
L
L
D000328:Adult; D001783:Blood Flow Velocity; D002986:Clinical Trials as Topic; D004311:Double-Blind Method; D005542:Forearm / Q000098:blood supply*; D006801:Humans; D007511:Ischemia / Q000503:physiopathology*; D008297:Male; D010146:Pain / Q000517:prevention & control*; D011983:Receptors, Purinergic / Q000187:drug effects*; D013806:Theophylline / Q000627:therapeutic use*; D013997:Time Factors
D011983:Receptors, Purinergic; D013806:Theophylline