Millions of patients are currently taking beta-blockers for conditions including hypertension, coronary heart disease, and arrhythmias. The most widely prescribed beta-blockers are metoprolol (Toprol, Lopressor) and carvedilol (Coreg). If you are taking a beta-blocker, you are likely taking one of them. 

I rarely prescribe either of these two best-sellers. 

Here’s why.

There are two types of beta-blockers: “lipophilic” and “non-lipophilic.” Metoprolol and carvedilol are “lipophilic” beta-blockers. Few physicians and patients are aware of this important distinction. They are also unaware of two important and common problems associated with lipophilic beta-blockers, and even more important, the quick and simple solution to those problems.   

Problem #1: Unpredictable blood levels of the drug

Lipophilic beta-blockers such as metoprolol and carvedilol are metabolized first-pass by the liver. Studies have clearly established that the rate at which they are metabolized differs considerably among patients and that blood levels of the drug can vary 10-fold or more from one patient to another.  If you are a rapid metabolizer, the blood level is often too low to provide the intended effect. If you are a slow metabolizer, the blood level can be much higher than necessary, and you are more likely to have side effects, such as fatigue. 

Problem #2: A common, avoidable side effect that many, without knowing it, are living with Lipophilic beta-blockers, such as metoprolol and carvedilol, penetrate the blood/brain barrier and studies show it can accumulate in brain tissue. 

Very few patients and physicians are aware of a side effect that can result from this: patients tend to describe it as “mental dullness,” or “brain fog,” or more subtly as feeling “less sharp” than they used to.  When it is subtle, many patients assume it’s simply something that comes with age. So they never mention it to the doctor and remain on the medication for years. 

But, in many, it is not subtle. Many describe it as mental dullness or even brain fog. Sadly, few realize that the medication is the cause. At its worst, in a small number of patients, it can mimic early Alzheimer’s Disease. My most memorable patient was an elderly patient who seemed to have mild dementia. I switched her beta-blocker to a non-lipophilic one. At her return visit, her daughter said to me: “Thank you for giving me back my mother!”   

Making matters worse, no studies discuss this side effect of mental dullness, or how common it is! My clinical experience suggests that it occurs in as many as 10% or more of patients taking metoprolol or carvedilol; i.e. potentially millions of patients. And sadly, most patients remain on the medication indefinitely! 

The simple, easy-to-try alternative?

There is actually, a quick and easy solution to the problem: switch to a “non-lipophilic beta-blocker or to a different class of medication. If the beta-blocker you are taking is in fact causing mental dullness, you will see the difference quickly, within a few days. Over decades of clinical practice, I have observed this response in many patients. It is very simple to switch to a different beta-blocker, and there is usually no reason whatsoever to not try this simple alternative.  

If you are taking metoprolol or carvedilol and have no problem, I wouldn’t routinely change the medication.

However, if you are aware of a reduction of your mental sharpness, whether subtle or overt, it might be linked to the metoprolol or carvedilol, and you need to find out by changing the medication. 

The non-lipophilic beta-blocker I usually prescribe is bisoprolol, which is inexpensive and readily available. It provides a much more predictable blood level, with much less penetration of the blood-brain barrier. For most patients, a typical dose is either half or a whole 5 mg pill. A few require a higher dose. 

Most physicians are unaware of and have never prescribed bisoprolol. Why? I think the only reason is that it was not marketed well. That’s why you will likely have to suggest it to your physician. 

Carvedilol differs from metoprolol in that it blocks both beta- and alpha-receptors. This is a major advantage because blocking both receptors is more effective in reducing blood pressure reactivity and in lowering blood pressure. 

Replacing carvedilol often requires a combination of two medications: bisoprolol to block the beta-receptors, and doxazosin, to block the alpha-receptors. There are literally no published studies that have directly compared the effectiveness of carvedilol vs. this combination in terms of effectiveness in lowering blood pressure. However, available information from studies, as well as my clinical experience, strongly indicate that this combination is often much more effective than carvedilol in lowering blood pressure.

So, to sum up, if you are taking a beta-blocker, please keep these important points in mind:

1. The unpredictable blood levels of metoprolol and carvedilol
2. Their not uncommon adverse effect on mental sharpness
3. The very simple solution 

Ask your doctor about this but, remember, most physicians are unaware of these issues.

Bring the link to this blog post with you. If you think you are less sharp than you used to be or are experiencing what you would describe as a bit of mental dullness, the only way you can find out is to communicate this to your doctor and request a trial of bisoprolol. Or, if your doctor thinks you might not need a beta-blocker, he could alternatively switch you to a different type of medication.

Clearly, more research is needed to further characterize this problem, but that could take years. In the meantime, effective action is possible, now. Please share this blog with as many people as you can, to bring to their attention both this important yet rarely recognized problem, as well as the very easy yet rarely offered solution. 

Please note: In recommending bisoprolol, I have no financial conflict of interest whatsoever. 

If you have any suspicion about your mental sharpness, you can quickly and easily find out if metoprolol or carvedilol is contributing to it.