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Thread: clonodine

  1. #11
    Senior Member nat007's Avatar
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    Ok, interesting.. I never realized this interaction between clonidine and propranolol. Sorry for sounding really dim here, but I'm a foreigner and no med student and find it hard to fully grasp what you are quoting. Would you be so kind to explain it in children's language? I just don't understand it fully.

    Propranolol is prescribed for high blood pressure patients, but it has the potential to actually raise blood pressure only further, due to it's simulation of the effect of norepinephrine on the receptors that narrow blood vessels? Does it have this dual action mode by itself (and if so, what sane doctor would prescribe it then for people with risky high blood pressure? I know at least 3 elderly relatives or friends who use it for that purpose), or only when combined with another blood pressure lowering med, like clonidine? If the two cancel each others effect out, would it be wise then to stop with one of the two (when someone takes both propranolol and clonidne for facial flushing for instance)? To avoid extra redness and high blood pressure risk?

    Thanks for your input, best wishes
    Uses: 22,5 mg mirtazapine, clonidine and propranolol, Xyzal at times.
    Diet: trying low sugar, no gluten and dairy, high protein diet.
    Link to my rosacea blog:http://scarletnat.blogspot.com

  2. #12
    Senior Member nat007's Avatar
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    Quote Originally Posted by y-gwair View Post
    What you are describing is reflex peripheral vasoconstriction, which is a general effect of most betablockers, including those like atenolol that are selective for beta 1 receptors which are found mainly around the heart. Propranolol affects both beta 1 and beta 2 receptors, which are found in blood vessels throughout the body. To quote wikipedia:

    "Research has also shown that propranolol has inhibitory effects on the norepinephrine transporter and/or stimulates norepinephrine release (present experiments have shown that the concentration of norepinephrine is increased in the synapse but do not have the ability to discern which effect is taking place).Since propranolol blocks β-adrenoceptors, the increase in synaptic norepinephrine only results in α-adrenergic activation, with the α1-adrenoceptor being particularly important for effects observed in animal models. Therefore, some have suggested that it be looked upon as an indirect α1 agonist as well as a β antagonist. "

    Alpha agonists increase blood pressure by simulating the effect of norepinephrine on the receptors that narrow blood vessels. Clonidine is an alpha 2 agonist, which means that it also narrows blood vessels. As it also lowers BP by tricking the brain into stimulating less norepinephrine from the adrenal glands, the effect in most people is that these two different effects cancel each other out, but this isn't necessarily the case if you take other medications that interact to alter this balance, including propranolol, over-the-counter drugs like pseudoephedrine, dental adrenalin, neuropathic painkillers such as nortriptyline etc etc.

    I think most people who suffer flushing/burning face problems, so-called 'vascular rosacea', probably have some level of autonomic disturbance and hypersensitivity to neurotransmitters. For most people, this will probably just be localised nerve damage/supersensitivity to neurotransmitters in the face, but for a minority of people like myself it may also be symptomatic of a wider problem that they might not be aware of until they start taking complex combinations of blood pressure drugs.


    This is an old post, but I came back onto it again. Looked for some science to back this up but I can't find it. I did come across this research:


    "Interaction of clonidine and beta-blockers.
    Lilja M, et al. Acta Med Scand. 1980.
    Show full citation
    Abstract
    On the hypothesis that non-selective beta-blockers can antagonize or reverse the antihypertensive effect of clonidine (C), 12 hypertensive outpatients were treated with C alone and in combination with propranolol (P), atenolol (A) and prazosin (Pz). C alone (0.11 or 0.22 mg b.i.d.) or in combination with P (80 mg b.i.d.) did not provide normotension. Changing P to A (50 mg b.i.d.) reduced supine systolic and diastolic pressures, which now were significantly lower (p less than 0.01) than during C alone. Changing A to P again resulted in elevated pressures. Pz (1 mg t.i.d.) added to the C+P regimen lowered supine blood pressures to the levels otherwise recorded during C+A. C dose-dependently contracted rabbit aortic spiral in vitro, reaching about 50% of maximum responses to noradrenaline. Pz abolished this response. P (0.1--10 micrograms/ml) but not A somewhat enhanced responses to high doses of C. Sotalol rather antagonized C contractions. We conclude that A but not P enhances the antihypertensive action of C. No hypertensive interaction was observed."
    https://www.ncbi.nlm.nih.gov/m/pubmed/6102839/


    Clonidine and the vasodilating beta blocker antihypertensive drug interaction.
    Pettinger WA, Mitchell HC, Güllner HG.
    Abstract
    Because propranolol is contraindicated in some patients and since clonidine can decrease heart rate and renin release, clonidine was substituted for propranolol in 14 severely hypertensive minoxidil-treated outpatients. Clonidine induced weight loss which, since plasma concentrations were not suppressed, was not due to inhibition of release of antidiuretic hormone or renin. These endocrine interrelations were confirmed by later administration of clonidine to 4 of the subjects under controlled circumstances in our General Clinical Research Center. When substituted for propranolol, clonidine controlled blood pressure and heart rate in 8 of the 9 outpatients whose blood pressure had been previously well controlled. Clonidine and propranolol had additive antihypertensive effects in the other 5 patients. Thus, clonidine can substitute for propranolol or when added to the propranolol-vasodilator combination supply an additional blood pressure-lowering effects. This substitution or addition results in an increase in side effects. In addition, clonidine has a diuretic action under these circumstances by an unknown mechanism.
    https://www.ncbi.nlm.nih.gov/pubmed/18312

    Long-term experience with the combination of clonidine and beta-adrenoceptor blocking agents in hypertension.
    Vanholder R, Lameire N, Ringoir S.
    Abstract
    The risk of cardiovascular and fatal complications and the antihypertensive effect of a clonidine-beta-blocker combination was studied in 98 patients and was compared with the results for a group of patients treated with other antihypertensive regimens. The profile of complications was similar in the two groups for a total follow-up period of more than 2000 treatment-months. Clonidine in combination either with propranolol or atenolol had a distinct antihypertensive effect. However, clonidine plus atenolol resulted in a more immediate and pronounced fall in blood pressure. It is concluded that the combination of clonidine and a beta-blocker is an effective antihypertensive medication, and that patients treated with it are apparently at no greater risk of serious cardiovascular incidents than are those treated with other regimens.


    I wonder if the blood pressure increasing effects you mentioned Y-gwair, when combining the two, is a more rare side-effect perhaps? Like serotonin syndrome that sometimes happens when combining certain antidepressants, but not always? I take propranolol and clonidine together for severe flushing and burning since 2006 and have low-normal blood pressure. Lower than before starting (not higher) but not dangerously low either.

    Anyway, an old post but caught my attention again.
    Uses: 22,5 mg mirtazapine, clonidine and propranolol, Xyzal at times.
    Diet: trying low sugar, no gluten and dairy, high protein diet.
    Link to my rosacea blog:http://scarletnat.blogspot.com

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