Today I’m starting a new series called The Med List. Once or twice a month, I’d like take a closer look at a single class of home medications and explore the medical implications for our patients who take these meds.
The patient’s medications list holds a wealth of information. Prescribed medications tell us about the patient’s medical history. They also give us clues to the patient’s possible current condition and presentation. Some medicines can better explain the clinical picture in front of us and others can be red flags regarding treatment options and the patients likely response.
Let’s kick off by looking a little closer at a class of medicines called Angiotensin Converting Enzyme Inhibitors. These meds are more commonly called ACE Inhibitors. Everyone calls ACE inhibitors ACE inhibitors in much the same way that everyone calls International Business Machines IBM and everyone calls American Telephone and Telegraph AT&T.
ACE Inhibitors are primarily used to treat high blood pressure but they have other uses outside of the hypertensive patient population. They may be taken by congestive heart failure patients to reduce the workload on the left ventricle. They are also prescribed to some renal failure patients and they may be useful in managing a percentage of scleroderma patients.
ACE inhibitors impair the body’s ability to constrict peripheral blood vessels by inhibiting the action of an enzyme essential to vasoconstriction. To understand how it works, we need to take a brief look at the renin-angiotensin system. (Don’t worry, this won’t be as painful as it sounds.)
Renin is an enzyme produced by the kidneys in response to low blood pressure, low blood volume, low sodium levels or renal stimulation. Once renin is excreted into circulation it goes immediately to the liver and asks if the protien angiotensin can come out and play. Angiotensin always does – angiotensin is just an easy going protien that way.
Angiotensin, fresh from the liver, may play a minor role in vasoconstriction, but it isn’t very potent. It’s called Angiotensin I and it’s like a boyscout without a vasoconstriction badge. It just isn’t up to the task. So what it really needs to do is go looking for a scout leader and get it’s, “I know how to constrict blood vessels” badge.
You’ve probably already guessed who plays the scout leader in this over-stretched analogy. None other than Angiotensin Converting Enzyme. That’s right. Once angiotensin I pairs up with an angiotensin converting enzyme (An ACE if you will.) it gets its badge and becomes angiotensin II, a powerful vasoconstrictor. Blood vessels beware.
As a clever way to prevent vasoconstriction, ACE inhibitors slow the action of the scout leaders, angiotensin converting enzymes, so far fewer angiotensin I’s are able to become angiotensin II’s. Make sense? If you find all this scout talk insulting, you can also read this much more technical and intelectual sounding version of the story.
So that’s what ACE inhibitors do, but what does that mean to us?
1) It means that they most likely have a history of high blood pressure or heart failure. In either case we should be cautious about excessive fluid administration, be extra careful when giving drugs that can lower the blood pressure. (Like nitro for instance.) And recognize that drugs that typically elevate the blood pressure (Like Epinephrine) may have a somewhat blunted effect.
2) It means that they have a significantly decreased capacity to elevate their blood pressure in the presence of sympathetic stimulation, compensated shock states and head injury. We should expect to see them transition from compensated to decompensated shock much more rapidly that a patient with fully functioning angiotensin converting enzymes.
3.) It means that if the patient (or anyone else) takes too many of this medication (accidentally or on purpose) we should expect to see a precipitous drop in blood pressure.
4) It means that the patient on ACE inhibitors may be at risk for hyperkalemia. The renal action of angiotensinII retains sodium and excretes potassium. Therefore we should consider the possibility of hyperkalemia and potentially dangerous heart arrhythmias in our assessment.
Clearly there are some compelling reasons to be able to spot an ACE inhibitor in the patients med list. The bad news is that there are a bunch of them being prescribed out there. The good news is that the generic names for all the varieties end with the letter combination pril. Here they are:
Benazepril (AKA Lotensin)
Captopril (AKA Capoten)
Enalapril (AKA Vasotec / Renitec)
Fosinopril (AKA Monopril)
Perindopril (AKA Coversy / Aceon)
Quinapril (AKA Accupril)
Ramipril (AKA Altace / Tritace / Ramace / Ramiwin)
If you’re paying attention to your patients medication lists, you’ve seen a bunch of these meds already. Fortunately, prescription pill bottles usually list both the generic and the trade name for the drug on the label. That gives us two chances to jog our memory.
But that’s not how med lists always come to us right? They come on wrinkled pieces of paper (Don’t lose that!) and printed computer sheets and patient charts and all other sorts of ways. It helps to be able to pick out an ACE inhibitor by either variety of names.