Clen headaches

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"The selectivity of b-adrenoceptor agonists at human b1-, b2- and b3-adrenoceptors"

This paper shows the receptor affinities of beta agonists. in the chart at the bottom, it show affinity and efficacy. Clen is by far on the beta 2 selective, and beta 2 efficacy side compared to beta 1.

the increase in HR is due to the vasodilation decreasing the preload and afterload, not directly due to the clenbuterol.

J Am Coll Cardiol. 1994 Apr;23(5):1224-33.
Positive inotropic effects of the beta 2-adrenoceptor agonist terbutaline in the human heart: effects of long-term beta 1-adrenoceptor antagonist treatment.
Schäfers RF, Adler S, Daul A, Zeitler G, Vogelsang M, Zerkowski HR, Brodde OE.
Source

Department of Internal Medicine, University of Essen, Germany.
Abstract

OBJECTIVES:

This study was conducted to determine whether activation of cardiac beta 2-adrenoceptors increases contractility in humans and whether this is affected by long-term beta 1-adrenoceptor antagonist treatment.

BACKGROUND:

Coexistence of beta 1- and beta 2-adrenoceptors in the human heart is generally accepted. The functional importance of cardiac beta 2-adrenoceptors for increases in contractility in humans, however, has not been completely established.

METHODS:

We studied 1) the beta-adrenoceptor subtype mediating positive inotropic effects of the beta 2-adrenoceptor agonist terbutaline in vitro (on right atrial and left ventricular preparations from nonfailing human hearts) and increases in contractility (by measurement of systolic time intervals) in vivo in seven healthy male volunteers; and 2) in vivo whether long-term treatment of volunteers with the beta 1-adrenoceptor antagonist bisoprolol affects terbutaline-induced increases in contractility.

RESULTS:

In vitro terbutaline caused a concentration-dependent increase in atrial and ventricular adenylate cyclase activity and force of contraction. Terbutaline effects were antagonized only by the beta 2-adrenoceptor antagonist ICI 118,551, indicating that they were mediated by beta 2-adrenoceptor stimulation. In vivo intravenous infusions of terbutaline (dose range 25 to 300 ng/kg body weight per min for 15 min) dose dependently increased heart rate and shortened the pre-ejection period and heart rate-corrected electromechanical systole (QS2) time. These effects are mediated predominantly by beta 2-adrenoceptor stimulation because they were only marginally affected by the beta 1-adrenoceptor antagonist bisoprolol (1 x 10 mg orally), either given 2 h before infusion or long term for 3 weeks.

CONCLUSIONS:

Stimulation of cardiac beta 2-adrenoceptors in humans causes not only in vitro but also in vivo positive inotropic effects. Long-term beta 1-adrenoceptor antagonist treatment does not considerably affect beta 2-adrenoceptor-mediated in vivo increases in contractility. Thus, it may be possible to treat patients with chronic heart failure and long-term beta 1-adrenoceptor antagonist therapy with beta 2-adrenoceptor agonists if immediate inotropic support is needed.

[Lemonada8]

J Am Coll Cardiol. 1994 Apr;23(5):1224-33.
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CONCLUSIONS:

Stimulation of cardiac beta 2-adrenoceptors in humans causes not only in vitro but also in vivo positive inotropic effects. Long-term beta 1-adrenoceptor antagonist treatment does not considerably affect beta 2-adrenoceptor-mediated in vivo increases in contractility. Thus, it may be possible to treat patients with chronic heart failure and long-term beta 1-adrenoceptor antagonist therapy with beta 2-adrenoceptor agonists if immediate inotropic support is needed.

ionotropic means strength of contractility, not increased HR. Thats chronotropic.

Beta2 do not increase HR directly. Some beta 2 agents can hit the Beta 1 receptor which will increase HR, but that has to do with the effficacy and affinity of the drug towards the beta 1 receptor.

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Don't give some wiki page to back that up, ESP when u know I'm pretty damn good in physio.
Whatever tho, in done with this debate. Agree to disagree

i am pretty rusty, in contrast. the last time i touch a physio book was 20yrs ago. thats why i like wiki, its written by smart people like you, and easily edited by other smart people if there is any inaccuracy:

Beta-2 adrenergic receptor
From Wikipedia, the free encyclopedia

Function

Actions of the β2 receptor include:

Circulatory system

Heart muscle contraction
Increase cardiac output (minor degree compared to β1).
Increase heart rate [11] in sinoatrial node (SA node) (chronotropic effect).
Increase atrial cardiac muscle contractility. (inotropic effect).
Increases contractility and automaticity[11] of ventricular cardiac muscle.
Dilate hepatic artery.
Dilate arteries to skeletal muscle.


http://en.wikipedia.org/wiki/Beta-2_adrenergic_receptor

ionotropic means strength of contractility, not increased HR. Thats chronotropic.

Beta2 do not increase HR directly. Some beta 2 agents can hit the Beta 1 receptor which will increase HR, but that has to do with the effficacy and affinity of the drug towards the beta 1 receptor.

and you already agreed that it increases contractility.