Blood clots are a serious business. They can restrict or even completely block blood flow to organs and extremities, causing things like pulmonary embolism, heart attack, stroke, ischemic bowel and even loss of limbs. So, it makes perfect sense that we want to prevent blood clots AND treat them when they occur. In this article, we’ll talk about what you need to know about anticoagulants for nursing school. Ready?

To prevent blood clots, we have a two-pronged approach: anticoagulants (like Coumadin or Heparin) and anti-platelet drugs (like Plavix). In general, we tend to call these “blood thinners” even though, technically, they don’t actually “thin” the blood. And if a blood clot is already formed, we go with clot-busting drugs (like TPA). Let’s break each of these down and talk about them in excruciating detail…ok just kidding…how about the highlights?


The traditional anticoagulants are Warfarin/Coumadin, Heparin and Lovenox/Enoxaparin. You’ll be using a fair amount of each of these, so it’s important to understand what they are and the nursing implications for each of them.

Warfarin/Coumadin: If you’ve heard some rumors about Coumadin being rat poison, you heard right! Not that it actually “poisons” rats, but the drug does cause the poor creatures to bleed out…it’s a very effective “blood thinner” in that regard! Note, however, that Coumadin doesn’t actually “thin” the blood….the term “blood thinner” is used as a broad term for meds that reduce blood clots, but what Coumadin actually does is lengthen the amount of time it takes for a blood clot to form.

The dose for Coumadin varies and is constantly adjusted by the pharmacy based on the INR with a target range typically 2.0-3.0). When the INR is within this range, we say “the INR is therapeutic” meaning that the higher-than-normal INR is expected AND desired. Note that there are a few conditions which have a slightly higher range, so if you work in a cardiac unit some of your patients may have a goal of 2.5-3.5 (depending on the type of valve replacement). But in general, if you go with 2.0-3.0, you’ll be in the right ballpark when it comes to your Med/Surg exams and NCLEX.

How does Coumadin work? Coumadin is a PO drug that inhibits the synthesis of clotting factors, mainly the ones related to Vitamin K (Factors II, VII, IX and X; and proteins C and S…but you probably don’t need that much detail!). The key here is VITAMIN K. Why?

What happens if your patient has taken TOO much Coumadin? The antidote for Coumadin is…VItamin K! You can also give FFP (fresh frozen plasma) or prothombin complex concentrate…these basically include those clotting factors that Coumadin exerts its effects on.

So, who is going to take Coumadin? Coumadin is used for patients who have DVT, a history of DVT, pulmonary embolism, heart valves or stents, atrial fibrillation, and s/p myocardial infarction. One of the BIGGEST misconceptions about Coumadin is that your patient cannot ever ever ever have leafy greens ever again. This is absolutely not true. What IS true, is that your patient’s intake of leafy greens (and essentially any food high in Vit K) must be consistent. So, if they like to have spinach salad, they need to have the same amount of greens every day.

PO medication
requires frequent lab draws
dietary intake of leafy greens (Vit K) must be consistent

dose is adjusted based on INR (goal 2.0 – 3.0)
reversal is Vit K and FFP/clotting factors

Heparin: Heparin is an injectable/IV medication used a lot in the clinical setting for patients who are at risk for blood clots. You’ll see it prescribed for patients who have a-fib, who need DVT/Pulmonary Embolism prevention, patients who have an arterial clot or need to prevent arterial clots (I see this a lot in the lower legs) and, lastly, patients in DIC (which deserves an entire post of its own!).

You will either be giving heparin as a SQ injection or an IV infusion. If your patient is on a heparin gtt, then they are needed some serious anticoagulation! This would be your patient who presented to the hospital with acute coronary syndrome, a PE or a DVT.

One of the things you want to be aware of is if your patient has an epidural, will have an epidural or any kind of spinal puncture. Anytime you start messing with the spine, you’ve got to be highly vigilant for hematomas…and having “thinned blood” would make a hematoma in this area more likely (and the result could be compression on the spinal nerves and paralysis…just don’t go there!)

Heparin works by inactivating thrombin and factor X, so the lab value you are going to follow is the PTT (partial thromboplastin time). If

SQ dose is typically standard (5,000 units is common)
infusion dose is adjusted based on PTT and goals of therapy
no spinal punctures or epidurals

reversal is protamine sulfate

Lovenox/Enoxaparin: Lovenox is a “low molecular weight heparin” used for DVT/PE prophylaxis (especially in patients receiving surgery) and the long-term outpatient treatment to prevent DVT/PE (most commonly) and also prophylaxis for ischemia related to cardiac problems such as angina and MI.

Like the other blood thinners listed above, Lovenox works on those clotting factors, but we don’t adjust the dose based on the PTT (though in suspected cases of overdose, you certainly could.) The dose is actually related to what the Lovenox is being used for (knee surgery vs abdominal surger vs unstable angina, etc….) In many cases, the dose is weight based (1mg/kg) AND adjusted for renal impairment. This is big…if your patient has renal impairment, you want to make sure you ask for “RENAL DOSING.”

given by SQ injection
dose is adjusted for renal impairment
no spinal punctures or epidurals

reversal is protamine sulfate

New Generation Anticoagulants

You’ve seen the commercials touting the beautiful, wonderful, freeing benefits of these next generation anticoagulants….the main point being that they don’t require the level of monitoring you see with Coumadin. Gone are the days of going to the “coumadin clinic” to get your blood drawn every week or every 2 weeks…you take your medication and go on about your life. But is it really that simple? Let’s take a look at these as a whole as they all are similar enough to talk about them in a broad sense…the list of drugs are:

  • Xarelto/Rivaroxaban
  • Eliquis/Apixaban
  • Pradaxa/Dabigatran
  • Savaysa/Arixtra

The huge takeaways that you need to know about these newer blood thinners is that they don’t require constant monitoring and have no dietary restrictions, so your patient may find the therapy easier to adhere to. The other huge thing to know is that there is NO ANTIDOTE. Let that sink in for a bit. No. Antidote.

If your patient is taking one of these meds and starts bleeding (GI bleeds are really common) then there’s NO WAY TO STOP IT. You have to basically “chase” the blood loss with transfusions and hope you can keep ahead of it. In severe, severe cases the only thing that can be done is emergent dialysis. Here’s the thing…emergent/acute dialysis requires the placement of a pretty darn big catheter which brings with it a HUGE risk for bleeding. So there’s that.

In addition to GI bleeds with these drugs, the risk for a brain hemorrhage is also up there. So…if your patient presents with severe headache with or without a change in LOC, find out if they are on any of these drugs and hope for the best.

Personally, I have seen numerous tragic bleeds with these meds…brain bleeds, GI bleeds being the most common. In some cases, the patients died. In others, it was touch-and-go for a while. If you can get through the first 24 hours with no further complications, you are looking at things being ok.

PO medication
no regular monitoring or need for frequent lab visits
no need to limit Vit K intake
no spinal punctures or epidurals
teach pt to monitor for signs of bleeding


Platelet aggregation inhibitors

These drugs inhibit the ability of platelets to stick together, thereby reducing the risk of blood clot formation. The most common ones you’ll see are Plavix, Aggrenox, Brilinta and aspirin.

Plavix/Clopidogrel: You’ll see Plavix prescribed a lot for your patients who’ve had a stroke, MI, peripheral arterial disease, acute coronary syndrome or who have heart stents or valves. While there is no specific antidote for these types of drugs, the treatment in cases of overdose is to transfuse platelets.

PO medication
once per day dosing


Aggrenox: Aggrenox is a combo drug of aspirin AND dipyridamole (which prevents platelets from clumping, much like Plavix). It is used to reduce the risk of stroke in patients who are at risk. One of the biggest drawbacks to this med is that it can cause pretty unpleasant headaches in some people as therapy is initiated.

PO medication
twice per day dosing
combo of aspirin and a platelet inhibitor


Brilinta/Ticagrelor: Brilinta is used to reduce the risk of cardiovascular death, MI and stroke in patients who are at risk (a-fib, history of MI or ACS), and also used for platelet aggregation inhibition in patients with cardiac stents. Studies have shown that it Brilinta may be more effecting than Plavix, so it’s quite possible that you can expect to see more of it being used in the clinical setting.

PO medication
twice per day dosing
dyspnea is a side effect in about 14% of patients
can cause or exacerbate bradycardia arrhythmias


Aspirin: Though technically aspirin is a salycilate, it is typically used as an anti-platelet drug…it basically works by blocking COX activity of certain platelet enzymes (it’s much more complicated than this, but we’re not pharmacists so we’ll just leave it at that!). You’ll see aspirin used widely for patients who are at risk for clot formation…those with history of DVT/PE, patients with artificial hips and anyone at risk for an MI.

PO medication
once per day dosing
take with food


Clot-busting drugs

Finally we get to the Big Daddy drugs…the ones you use when a clot is present and you want to get rid of it! This is the one you’ve heard about for treating ischemic stroke…TPA (also known as Alteplase).

Alteplase/Activase: Alteplase is a tissue plasminogen activator, so you may sometimes just hear it referred to as TPA. It’s main use is for patients who have presented to the ED with stroke symptoms whose CT scan is NEGATIVE for a bleed. You’ll also see it used in patients with acute myocardial infarction, pulmonary embolism and arterial clots that are threatening the life of a limb.

In cases of stroke, TPA is given as a bolus within 3-4.5 hours of symptom onset. In cases of acute myocardial infarction, it can be given as a bolus or over 3 hours as an infusion. Another indication for TPA administration is an arterial clot…in this case, an IV catheter is placed AT the location of the clot (this is done in IR…interventional radiology) and a slow infusion of TPA is administered into the clot itself in order to break it up.

IV bolus dose or infusion
high risk of bleeding, including cerebral

many contraindications including recent history of bleeding
reversal is tranexamic acid

As you have probably guessed, the monitoring parameters for any of these medications have one thing in common:

severe, sudden onset headache
visual changes
any stroke-like symptoms
frank blood in stool or emesis
frank blood in urine
black, tarry stool indicating digested blood 
coffee ground emesis indicating digested blood
oozing from IV sites
weakness, paresthesia or paralysis of lower limbs (indicating hematoma)

Now that you know the basics for the main medications used to prevent/treat blood clots, I hope you feel more confident when taking care of these patients. And if you’ve read this far…go you! You’re amazing!

Review key pharmacology concepts and over 80 drug classes, each in 5 minutes or less, in my audio-based program Fast Pharmacology. This program is perfect for use while you’re in nursing school, studying for NCLEX, or wanting to gain confidence administering medications as a working nurse. Learn more here!


The information, including but not limited to, audio, video, text, and graphics contained on this website are for educational purposes only. No content on this website is intended to guide nursing practice and does not supersede any individual healthcare provider’s scope of practice or any nursing school curriculum. Additionally, no content on this website is intended to be a substitute for professional medical advice, diagnosis or treatment.