Alpha Blockers – Clinical Practice Pearls
Alpha blockers are most frequently used in clinical practice to manage symptoms of BPH and probably less commonly used for hypertension. Here are a few relevant clinical practice pearls that are important to remember.
Alpha blockers are notorious for causing low blood pressure which can lead to a syncope type situation. This is most likely to happen when the patient begins to take this medication. Practically, we’d like to start at a very low dose to try to ease this initiation period. YOU HAVE GOT TO WARN PATIENTS ABOUT THIS! With dose increases, you need to be aware of this potential adverse effect as well. Geriatric patients are at greater risk due to a reduced baroreceptor reflex. Geriatric patients are also likely to be taken numerous other medications that can contribute to hypotension. A patient on other blood pressure lowering medications may be at greater risk for substantial syncope. This adverse effect is one of the major reasons why we don’t use alpha blockers as a first line agent to manage blood pressure.
Alpha Blocker Selectivity
An alpha-blocker like tamsulosin is more selective for alpha-1a receptors which are preferentially found in the bladder. Because of this, there is potentially the hypotensive effect is less with this medication. There are other alpha blockers that are selective, but I seldom ever see them used. Like with virtually all medications, selectivity tends to disappear (or at least isn’t as prominent) as the dose increases. Because of tamsulosin’s selectivity for bladder tissue, you will NOT see this medication used to manage hypertension. Prazosin, terazosin, and doxazosin are examples of agents that are non-selective.
Floppy Iris Syndrome
Yes, alpha blockers have been shown to increase the risk for floppy iris syndrome. What do I do about this? Cataracts are common with geriatric patients and having surgery is often necessary. If I know that a patient is having trouble with their eyes and/or is considering surgery, I encourage them to discuss their alpha-blocker use with their eye doctor.
Be Aware of Alpha Agonists
Drugs that have alpha agonist activity will have the potential to raise blood pressure and worsen symptoms of urinary retention. Examples of medications that are alpha agonists include decongestants like phenylephrine and pseudoephedrine. I also have seen midodrine (case study) used to manage low blood pressure. This is an alpha agonist as well.
Flomax in Females?
Flomax is typically used for BPH, so why would you ever see it used for females? I have seen this used in females with bladder outlet obstruction. I don’t believe the evidence for its use is overwhelmingly strong, but in patients who have not benefitted from other procedures and medications, you may see it tried.