Antihypertensive Drugs: A Closer Look at Beta-Blockers

Beta-blockers are, in the simplest sense, heart medications for clients with hypertension that is mainly focused on the conduction system of the heart.

Just to refresh your memory, there are two ways to lower blood pressure.

  1. Relieving pressure from the pipes by decreasing fluid volume. These are your ACE inhibitors and diuretics.
  2. Decrease rate of conduction in the heart. These are your beta-blockers and calcium channel blockers.

Mechanism of beta-blockers

Beta-blockers are negative, chronotropic drugs that block that SA node from contracting excessively. Beta-blockers block the beta-adrenergic receptor also known beta-1 and beta-2. Beta-1 are receptors in the heart stimulates increased heart contraction. If stimulated, these beta receptors can cause contraction at higher rates. Similarly, this concept applies to beta-2 in the lungs.

Study tip: Beta-2 is for the lungs (since you have two lungs) and beta-1 is for the heart (since you have one heart)

Beta-2 agonist causes bronchial dilation. One typical example is albuterol. Dosing someone with albuterol will antagonize beta-2. However, it will also affect beta-1 which means that there will be a noticeable rise in your heart rate. This is the reason why treatment of beta-2 causes tachycardia in clients.

Beta-blockers block beta. Beta excited the heart. When the beta is blocked, the heart rate decreases. It’s as simple as that. Cool!

Beta-blockers make you LOL

According to the FDA, identification of these types of drugs must be through their suffix. One of the easiest ways to identify your beta-blockers is to know, by heart, that it can make you laugh out loud (LOL). Meaning, beta-blockers generic names end in –lol. A typical example is atenolol and metoprolol. 

Beta-blocker warnings – the 4 Bs

When giving beta-blockers to your clients, you have to watch out for these adverse effects.

Bradycardia

This is a condition wherein the heart rate of your client drops below 60 per minute. Yes, the goal of beta-blockers is to slow down the heart rate but that doesn’t mean killing your client in the process.

In giving anti-hypertensives, it is advised to give the client the least heavy doses first. Meaning, give your volume depleters first; this will be your diuretics, ACE inhibitors, ARBs, and potassium-sparing diuretics. Don’t opt for electrical or chronological conduction drugs until you have given the volume-depleting drugs and have thoroughly assessed your client’s vitals.

This thought is going to be very useful during exams with borderline, tricky questions. Remember, the most likely answer is holding the drug if the systolic pressure drops to 100.

Blood pressure is decreased

If you’re going to administer a couple of anti-hypertensive drugs, make sure that you ask yourself how safe is it to give. Always run scenarios inside your head especially in terms of the possible out if you gave beta-blockers with other anti-hypertensive drugs. Getting the blood pressure is the best way to assess the necessity of administering the drug. If the blood pressure has significantly dropped after an hour or so, chances are, you won’t be giving the drug.

Yes, we have mentioned that beta-blockers do not decrease blood pressure and only affects Beta-1 in the heart; however, if the stroke volume is decreased, the cardiac output is decreased as well. Low blood pressure is a possible side effect.

Bronchi constriction

Yes, it was mentioned that beta-blockers are for blocking Beta-1; however, there is a probability that Beta-2 can also be blocked. Though it may be specific, it can happen.

Blood sugar masking

If your client has low blood sugar, beta-blockers can mask the signs and symptoms of bradycardia.