The vasodilatory effect of alfuzosin and tamsulosin in passive orthostasis: a randomised, double-blind, placebo-controlled study.
OBJECTIVE
To compare in details the effects of urologically used alpha(1)-blockers alfuzosin and tamsulosin on the cardiovascular responses to passive orthostasis.


METHODS
The responses to passive orthostasis (tilt provocation at 60 degrees for 8 min) were measured in normotensive healthy volunteers with finger blood pressure method and whole-body impedance cardiography prior to the administration of the drugs as well as three days after the beginning of the randomised, double-blind medications. The parallel treatments were standard clinically used doses of alpha(1)-blockers alfuzosin (5 mg twice daily, n=10), tamsulosin (0.4 mg once daily, n=10), or placebo (n=11).


RESULTS
When measured prior to the head-up tilt test in supine position, neither alfuzosin nor tamsulosin significantly changed any of the cardiovascular variables. During the passive orthostasis, however, both tamsulosin and alfuzosin reduced systemic vascular resistance index compared to pre-drug responses (-540 and -462 dyns/cm(5)m(2), respectively, p<0.05). Both drugs also augmented orthostatic responses of heart rate (11 and 9 bpm, respectively, p<0.05) and cardiac index (0.50 and 0.40 l/min/m(2), respectively, p<0.05) but not those of stroke index when compared to the responses during placebo or before the administration of the drugs. The alfuzosin and tamsulosin groups did not significantly differ from each other in terms of any parameter.


CONCLUSIONS
Both alfuzosin and tamsulosin have clear cardiovascular effects, which are most strikingly evident in the influences on systemic vascular resistance and cardiac output.
Nieminen
Tuomo
T
Department of Pharmacological Sciences, Medical School, FIN-33014 University of Tampere, Finland. tuomo.nieminen@iki.fi
Ylitalo
Ritva
R
Kööbi
Tiit
T
Ylitalo
Pauli
P
Kähönen
Mika
M
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000328:Adult; D004244:Dizziness / Q000188:drug therapy*; D004311:Double-Blind Method; D005260:Female; D018475:Head-Down Tilt; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008297:Male; D011799:Quinazolines / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology*; D016683:Supine Position; D000077409:Tamsulosin; D014665:Vasodilator Agents / Q000494:pharmacology*
D000317:Adrenergic alpha-Antagonists; D011799:Quinazolines; D013449:Sulfonamides; D014665:Vasodilator Agents; C047638:alfuzosin; D000077409:Tamsulosin