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Yohimbine and beta-blockers

By Serge Kreutz

Version 1.4, July, 2010

Heart palpitations (fast or irregular heartbeat) and tachycardia (are common unpleasant side effects of yohimbine. These side effects are caused by increased adrenergic tone. Increased adrenergic tone results from catecholamines such as epinephrine (adrenalin), norepinephrine, and dopamine (chiefly secretions or byproducts of secretions of the medulla of the adrenal gland) that affect the sympathetic nervous system. While yohimbine counteracts the effects of catecholamines on alpha2-adrenergic receptors, its side effect of heart palpitations suggests that it, quantitatively or qualitatively, enhances the effect of catecholamines on beta1-adrenoreceptors. Roughly, beta1-adrenoreceptors have an influence mostly on heart function; increased stimulation of beta1-adrenoreceptors, either by catecholamines or pharmaceutical beta1-adrenoreceptor agonists, cause an increase in heart rate and blood pressure. Beta2-adrenoreceptors are, to a higher degree than beta1-adrenoreceptors, associated with bronchial and vascular musculature.

A standard treatment of tachycardia and palpitations is the application of beta-blockers These are drugs, such as propranolol, that oppose the excitatory effects of norepinephrine released from sympathetic nerve endings at beta-receptors; they are used for the treatment of angina, hypertension, arrhythmia, and migraine.

The Merck Manual on Diagnosis and Therapy notes (in its chapter on Mitral Valve Prolaps):

Symptoms of excess sympathetic tone, palpitations, migraine (not uncommon), and dizziness due to orthostatic hypotension can be relieved with beta-blockers. These may also raise the fibrillation threshold in patients with dangerous tachycardias."

An Internet site named Natural Medical Solutions notes:

"Metoprolol, penbutolol and propranolol protect against toxicity of yohimbine in animal studies."

The readers of my web site are aware that I regularly combine yohimbine with sildenafil citrate (Viagra). Beta-blockers don't seem to be contraindicated with Viagra. On the web site of the American Heart Association (in an article on Viagra), it is stated:

"In patients with recurring angina after Viagra use, other non-nitrate antianginal agents, such as beta-blockers, should be considered."

Based on the above information, I decided to try a combination of yohimbine with beta-blockers.

I have tested propranolol and metoprolol beta-blockers in combination with yohimbine. My own observations are included below. But first I do want to quote from the feedback of a reader:

"Greetings"

I am an emergency physician.

I'll use medical jargon because you can understand it rather than writing at a grade school level.

Beta-blockers (inderal, atenolol, pindolol, etc.) block the beta adrenergic effect, resulting in vasodilation, decreased heart rate, etc. In the presence of yohimbine blocking the CNS alpha-2 receptors, central adrenergic stimulation is removed, leading to unchecked peripheral adrenergic stimulation.

In the presence of a beta-blocker [when using yohimbine] one may end up with undesirable unopposed nor-adrenergic stimulation, resulting in very high blood pressure, and possibly a heart attack or  a stroke  in susceptible people; of course that result is likely to be dose dependent."

Propranolol hydrochloride (abbreviated here as Propranolol HCl), a synthetic beta-adrenergic receptor blocking agent. Propranolol HCl is available as 10 mg, 20 mg, 40 mg, 60 mg, and 80 mg tablets for oral administration. "Inderal" is one of the most common brand names. Indications for propranolol include: Hypertension, Cardiac Arrhythmias, Myocardial Infarction (Propranolol HCl is indicated to reduce cardiovascular mortality in patients who have survived the acute phase of myocardial infarction and are clinically stable), Migraine (Propranolol HCl is indicated for the prophylaxis of common migraine headache). Potential adverse reactions of propranolol include: Bradycardia; congestive heart failure; hypotension, mental depression manifested by insomnia, lassitude, weakness, fatigue, and vivid dreams.

Metoprolol tartrate, a selective beta1-adrenoreceptor blocking agent, available as 50- and 100-mg tablets for oral administration. The most common brand name is "Lopressor". Metoprolol tartrate is indicated in the treatment of Hypertension, Angina Pectoris, and Myocardial Infarction (to reduce cardiovascular mortality). Tiredness and dizziness are adverse reactions that have occurred in about 10 of 100 patients. Depression has been reported in about 5 of 100 patients. Mental confusion, short-term memory loss, headache, nightmares, and insomnia have also been reported. Shortness of breath and bradycardia (slow heart rate, usually of fewer than 60 beats per minute) have occurred in approximately 3 of 100 patients. Also, palpitations and congestive heart failure (a condition marked by weakness, edema, and shortness of breath that is caused by the inability of the heart to maintain adequate blood circulation in the peripheral tissues and the lungs) have occurred. Hypotension has been reported in about 1 of 100 patients. Wheezing (bronchospasm) and dyspnea (shortness of breath) has been observed in about 1 of 100 patients.

I found metoprolol's effect of slowing down heart rate considerably stronger than propranolol's. Actually, it slowed down my heart to an extend where I almost couldn't feel a heart beat at all. This doesn't worry me when I'm not on anything, but surprised me while on yohimbine. However, metoprolol also didn't solve the insomnia problem, so I had no incentive to continue my experiments.

For a solution to the sleeplessness problem when on yohimbine, please see our new domain www.yohimbine.org.

I have found clonidine to be a complete antidote to yohimbine. And indeed, it can be used to treat a yohimbine overdose. The clonidine dosages I have tried were 75 and 150 micrograms (NOT milligrams). I have found that it slowed down heart rate and reduced the mental stimulation caused by the yohimbine. However, even 150 micrograms were not enough to allow me to get to sleep earlier than 20 hours after the yohimbine ingestion.

Clonidine's possible side effects include sexual dysfunction; as clonidine clearance can take considerably longer than 24 hours, I decided against its further use. My main objective in using it would have been to combat the insomnia caused by yohimbine. It didn't work to that end.