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 medical decision-too little anticoagulation and you risk a stroke or pulmonary embolism; too much and you could bleed internally. This is where bridging therapy comes in. But here’s the twist: for most people, you don’t need it at all.

What Is Bridging Therapy, Really?

Bridging therapy means temporarily replacing a long-acting blood thinner like warfarin with a fast-acting injectable one-usually low molecular weight heparin (LMWH)-while you pause your regular medication for surgery or a procedure. The idea was simple: keep your blood from clotting during the gap. But over the last decade, evidence has flipped this thinking on its head.

The BRIDGE trial in 2015 changed everything. Researchers gave over 2,000 patients with atrial fibrillation either bridging with LMWH or no bridging while they stopped warfarin before surgery. The result? Bridging didn’t lower stroke risk-but it doubled the chance of major bleeding. That’s not a trade-off worth making for most people.

Today, guidelines from the American Heart Association and American College of Cardiology say: only bridge if you’re at very high risk of clots. That means you have a mechanical heart valve in your mitral position, or you had a blood clot in the last three months. Everything else? Skip the injections. Keep your DOACs going, adjust the timing, and move on.

When Bridging Is Still Necessary

Not everyone can stop their blood thinner without risk. If you fall into one of these categories, bridging might still be your safest path:

• You have a mechanical mitral valve (not just any valve-this one’s high-risk)
• You had a deep vein thrombosis or pulmonary embolism in the past 3 months
• Your CHA₂DS₂-VASc score is 7 or higher (that’s severe atrial fibrillation risk)

For everyone else-especially those with non-valvular atrial fibrillation, even with a score of 5 or 6-bridging does more harm than good. The 2021 AHA guidelines cut the number of patients eligible for bridging from half to just 10-15%. That’s a massive shift in practice.

Why? Because the bleeding risk from LMWH injections is real. In the BRIDGE trial, 2.3% of bridged patients had major bleeding. Only 1% of those who didn’t bridge did. That’s a 130% increase in bleeding risk for zero protection against clots.

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

Not all blood thinners are created equal. Warfarin (Coumadin) is old-school. It takes days to build up in your system and even longer to clear out. That’s why you stop it 5-6 days before surgery and wait for your INR to drop below 1.5. That gap? That’s where bridging used to fill in.

But DOACs-like apixaban (Eliquis), rivaroxaban (Xarelto), and dabigatran (Pradaxa)-are different. They work fast and leave fast. Their half-lives range from 5 to 17 hours, depending on your kidney function. That means:

• You can stop apixaban 24-48 hours before surgery
• Stop dabigatran 48 hours before if your kidneys are normal
• Stop rivaroxaban 24-48 hours before, depending on bleeding risk

No bridging needed. No injections. No extra cost. No risk of heparin-induced thrombocytopenia (a rare but dangerous immune reaction to heparin). That’s why DOACs now make up 75% of new anticoagulant prescriptions in 2023. They’re simpler, safer, and eliminate the need for bridging in most cases.

How Bridging Therapy Works (If You Need It)

If you’re one of the few who still need bridging, here’s how it’s done-step by step, based on current protocols:

1. 10 days before surgery: Your doctor checks your clotting risk (CHA₂DS₂-VASc) and bleeding risk (HAS-BLED). They also test your kidney function and screen for heparin-induced thrombocytopenia.
2. 5-6 days before: You stop taking warfarin. Your INR should drop below 1.5 by this point.
3. 3 days before: You start daily injections of LMWH (like enoxaparin). Dose is usually 1 mg/kg twice daily if you’re at high clot risk.
4. 24 hours before: You stop the LMWH. No exceptions. Even one injection too close to surgery can cause serious bleeding.
5. After surgery: Restart LMWH 24-48 hours after, depending on bleeding risk. Then restart warfarin at 15-20% higher than your previous dose. Check your INR in 3-4 days.

Timing is everything. Miss a dose? Go too early? Too late? You’re either clotting or bleeding. That’s why this isn’t a DIY process. It needs coordination between your cardiologist, surgeon, and pharmacist.

The Hidden Costs of Bridging

It’s not just about bleeding risk. Bridging therapy is expensive, inconvenient, and risky in ways people don’t talk about.

A 7-day course of LMWH in the U.S. costs $300-$500. In the UK, NHS prescriptions cover it, but patients still face logistical headaches-daily injections, cold storage, travel to clinics. Studies show 15-20% of patients miss at least one injection. That’s not just non-adherence-it’s a ticking time bomb.

And then there’s the confusion after surgery. When do you restart warfarin? How much? Do you keep the LMWH? Many patients are sent home with conflicting instructions. That’s why post-op bleeding is often linked to poor communication-not poor medicine.

What About Switching From DOACs to Warfarin?

Sometimes, you need to go the other way-switching from a DOAC to warfarin. Maybe your kidney function changed. Maybe your insurance dropped coverage. Or maybe you’re pregnant (DOACs aren’t safe in pregnancy).

Here’s how it’s done safely:

• Stop the DOAC. Wait until it’s cleared from your system (24-48 hours, depending on the drug and kidney function).
• Start warfarin at your usual maintenance dose, but add a parenteral anticoagulant (like LMWH) for overlap.
• Keep the LMWH going until your INR is therapeutic (2.0-3.0) for at least two consecutive days.
• Then stop the LMWH. No bridging needed here-just overlap.

Important: Don’t start warfarin too early. If you give it while the DOAC is still active, your INR might spike dangerously high. That’s why doctors often check a baseline INR before stopping the DOAC.

What You Can Do Right Now

If you’re on a blood thinner and have surgery coming up, here’s what to do:

• Ask your doctor: "Am I at high risk for clots?" If yes, what’s your CHA₂DS₂-VASc score?
• Ask: "Do I need bridging?" If they say yes, ask for the evidence. Are you on a mechanical mitral valve? Had a clot in the last 3 months?
• If you’re on a DOAC, ask: "Can I just delay my dose instead of switching?" The answer is likely yes.
• Get a written plan. Not just a verbal one. Include exact dates for stopping and restarting meds.
• Confirm with your surgeon and pharmacist. Miscommunication kills.

Most people think more anticoagulation = safer. But in reality, less is often more. The goal isn’t to keep your blood from clotting at all costs. It’s to keep you alive without making you bleed.

What’s the Future of Bridging?

Bridging therapy isn’t disappearing-it’s narrowing. It’s becoming a tool for a tiny fraction of patients, not a default for everyone on warfarin.

As DOACs keep replacing warfarin, the need for bridging will drop further. New guidelines are already moving toward "step-up" approaches: start with low-dose anticoagulants after surgery, then ramp up only if needed. That’s safer, simpler, and less invasive.

The real win? Patients are getting back control. No more daily shots. No more INR checks every week. No more panic when a procedure gets rescheduled. Just a simple, timed pause-and a return to normal life.

If you’re on blood thinners, don’t assume bridging is the norm. Ask the questions. Demand the data. Your body will thank you.