Bridging Therapy: How to Safely Switch Between Blood Thinners

Switching between blood thinners isn’t something you do on a whim. It’s a high-stakes move that can mean the difference between a clot forming in your heart or leg - or bleeding out during a simple procedure. For years, doctors routinely used bridging therapy to keep patients protected when stopping long-acting blood thinners like warfarin for surgery or dental work. But today, that practice is changing - fast. Most people don’t need it anymore. And if you’re still being offered bridging without a clear reason, you should ask why.

What Is Bridging Therapy, Really?

Bridging therapy means using a short-acting injectable blood thinner - usually low molecular weight heparin (LMWH) like enoxaparin - to cover the gap when you stop your regular blood thinner before a procedure. The idea was simple: if warfarin wears off slowly, and your clotting risk stays high during that time, inject a fast-acting anticoagulant to fill the gap.

It made sense on paper. But real-world data tells a different story. The landmark BRIDGE trial in 2015 showed something startling: patients who got bridging had a 2.3% risk of major bleeding, while those who didn’t get bridging had just a 1.0% risk. And here’s the kicker - there was no difference in stroke or clot risk between the two groups.

That study changed everything. It proved what many doctors suspected: bridging doesn’t prevent clots - it just makes you bleed more.

When Do You Actually Need Bridging?

Not everyone needs it. In fact, most people don’t. Current guidelines from the American Heart Association and the American College of Cardiology now limit bridging to just two groups:

• People with mechanical heart valves, especially in the mitral position
• Those who’ve had a blood clot within the last 3 months

That’s it. If you have atrial fibrillation but no mechanical valve and no recent clot? You’re not a candidate. If your CHA₂DS₂-VASc score is 5 or higher, but you’ve been stable on warfarin for years? Still not enough. The risk of bleeding from bridging outweighs the tiny benefit.

Here’s why: the body doesn’t turn off clotting overnight. Even when warfarin is stopped, your blood doesn’t instantly become "thin". That’s why stopping warfarin 5-6 days before surgery gives your body time to clear it naturally. For most people, that’s enough.

Warfarin vs. DOACs: Why One Needs Bridging and the Other Doesn’t

Not all blood thinners are created equal. Warfarin has a long half-life - around 40 hours. That means it sticks around for days. That’s why you need to stop it early and plan for bridging.

But direct oral anticoagulants (DOACs) like apixaban (Eliquis), rivaroxaban (Xarelto), and dabigatran (Pradaxa) work differently. They clear from your system in hours, not days. Apixaban? Half-life of 12 hours. Rivaroxaban? 7-11 hours. Dabigatran? 12-17 hours, depending on kidney function.

Because of this, bridging is not recommended for DOAC users. You simply stop the pill a day or two before your procedure - depending on your kidney health and the bleeding risk of the surgery - and restart it within 24 hours after. No injections. No heparin. No extra risk.

In 2023, DOACs made up 75% of all new anticoagulant prescriptions in the U.S. That’s not a coincidence. They’re easier. Safer. And they’ve made bridging therapy obsolete for the vast majority of patients.

How Bridging Therapy Works - Step by Step (If You Really Need It)

If you’re one of the rare cases that still needs bridging, here’s what the process looks like - based on current hospital protocols like those at Holy Cross Hospital and updated by the American Heart Association in 2020:

1. 10-14 days before surgery: Your doctor checks your clotting risk (CHA₂DS₂-VASc) and bleeding risk (HAS-BLED). They also test your kidney function and check for heparin-induced thrombocytopenia (HIT), a rare but dangerous reaction to heparin.
2. 5-6 days before surgery: You stop taking warfarin. Your INR (a blood test that measures clotting time) should drop below 1.5 by this point.
3. 3 days before surgery: You start twice-daily injections of LMWH (like enoxaparin). This keeps your blood thin during the warfarin gap.
4. 24 hours before surgery: You stop the LMWH injections. This gives your body time to clear it before the procedure.
5. After surgery: You restart LMWH 24-48 hours after the procedure - once bleeding risk has dropped. Warfarin is restarted at 15-20% higher than your previous dose, and your INR is checked in 3-4 days to find your new therapeutic range.

This timeline isn’t flexible. Missing an injection or restarting too early can lead to clots. Restarting too late can cause bleeding. That’s why coordination between your cardiologist, surgeon, and pharmacist is critical.

The Hidden Costs - More Than Just Money

Bridging therapy isn’t just risky - it’s expensive. A 7-day course of LMWH in the U.S. costs between $300 and $500. In the UK, NHS patients get it free, but the logistical burden is still heavy.

Many patients struggle with the injections. Studies show 15-20% of people miss at least one dose. Some can’t afford the time. Others are afraid of needles. Some don’t understand why they’re doing it - especially when they’re told, "Just in case."

And then there’s the emotional toll. You’re not just managing a pill anymore. You’re managing needles, schedules, hospital visits, and fear. That’s why many patients now ask: "Is this really necessary?" And increasingly, the answer is no.

What Happens After the Procedure?

Restarting your blood thinner after surgery is just as important as stopping it. Too soon, and you bleed. Too late, and you clot.

For warfarin patients on bridging: restart warfarin 24-48 hours after surgery. Don’t restart the LMWH until after you’ve taken your first warfarin dose. Then, keep the LMWH going for 3-5 days until your INR is back in range.

For DOAC patients: restart within 24 hours if the procedure was low-risk (like a colonoscopy). Wait 48-72 hours if it was high-risk (like open-heart surgery). Always check with your doctor - your kidney function matters.

Never guess. Always get your INR or anti-Xa levels checked after restarting. A single missed check can lead to disaster.

Why Doctors Still Recommend Bridging - Even When They Shouldn’t

Despite the evidence, some doctors still default to bridging. Why?

• Habit: They’ve been doing it for 15 years. Changing feels risky.
• Fear of lawsuits: "What if they clot?" is louder than "What if they bleed?"
• Lack of training: Many providers aren’t updated on 2020-2023 guidelines.
• Pressure from surgeons: Some surgeons still ask for bridging out of old protocol.

But the tide is turning. The ACC’s "Primum Non Nocere" principle - "First, do no harm" - is now guiding decisions. And the data is clear: for most people, the harm of bridging outweighs any benefit.

Your Action Plan: What to Ask Your Doctor

If you’re on a blood thinner and have a procedure coming up, here’s what you need to ask:

• "Am I on warfarin or a DOAC?"
• "Do I have a mechanical heart valve or a clot in the last 3 months?"
• "Is bridging recommended for me, and why?"
• "What’s the evidence behind this decision?"
• "Can I just stop my pill and restart it after without injections?"
• "Who will coordinate my stop and restart dates?"

If your doctor says, "We always bridge for atrial fibrillation," push back. That’s outdated. If they say, "It’s just a precaution," ask what the risk is - and whether that precaution is more dangerous than the thing it’s trying to prevent.

The Future of Blood Thinners - Less Bridging, More Simplicity

The future is clear: DOACs are replacing warfarin. More than 75% of new prescriptions are for DOACs. Why? Because they don’t need bridging. They don’t need monthly blood tests. They don’t interact with broccoli or vitamin K.

As more patients switch to DOACs, bridging therapy will become a relic - used only in rare, high-risk cases. And that’s a good thing. It means fewer needles, fewer hospital visits, less fear, and fewer bleeds.

If you’re still on warfarin and wondering whether to switch, talk to your doctor. The benefits of DOACs go beyond convenience - they’re safer. And they eliminate the need for bridging altogether.