A case report from 2026 shows that the antibiotic cefoperazone/sulbactam caused a patient’s blood clotting time to increase from normal (11-13.5 seconds) to dangerously prolonged (262.9 seconds) after eight days of treatment. According to Gram Research analysis, the antibiotic likely interfered with vitamin K, which is essential for blood clotting. The problem reversed within three days of stopping the medication and receiving vitamin K treatment, suggesting this is a serious but reversible side effect doctors should monitor for, particularly in patients with digestive problems or those receiving IV nutrition.
A patient taking the antibiotic cefoperazone/sulbactam developed a serious blood clotting disorder while receiving nutrition through an IV and being treated for a brain infection. According to Gram Research analysis, the antibiotic appeared to interfere with vitamin K, a nutrient essential for normal blood clotting. Within days of stopping the medication and receiving vitamin K treatment, the patient’s blood clotting returned to normal. This case report highlights an important but rare side effect that doctors should watch for when prescribing this antibiotic, especially in patients with digestive problems or those receiving IV nutrition.
Key Statistics
A 2026 case report documented that cefoperazone/sulbactam caused a patient’s prothrombin time to extend to 262.9 seconds—approximately 20 times longer than the normal range of 11-13.5 seconds—after eight days of antibiotic treatment.
The patient’s dangerous blood clotting dysfunction reversed completely within three days of discontinuing cefoperazone/sulbactam and receiving vitamin K supplementation and plasma transfusion, indicating the adverse effect is rapidly reversible.
Using the Naranjo Adverse Drug Reaction Probability Scale, doctors determined a score of 7, indicating a probable causal relationship between cefoperazone/sulbactam use and the severe coagulation dysfunction observed in this patient.
The Quick Take
- What they studied: Whether the antibiotic cefoperazone/sulbactam can cause dangerous blood clotting problems in patients receiving IV nutrition
- Who participated: One patient admitted to the hospital with a brain bleed who had a stomach/digestive problem and was receiving all nutrition through an IV
- Key finding: The patient’s blood clotting time became dangerously prolonged (262.9 seconds, when normal is 11-13.5 seconds) after 8 days of antibiotic treatment, but returned to normal within 3 days of stopping the medication and receiving vitamin K
- What it means for you: If you’re taking this antibiotic and have digestive problems or receive IV nutrition, doctors should monitor your blood clotting regularly. This is a rare side effect, but knowing about it helps doctors catch and treat it quickly
The Research Details
This is a case report, which means doctors documented what happened to one specific patient. The patient came to the hospital with a serious brain bleed caused by a bacterial infection (Klebsiella pneumoniae). Because the patient couldn’t eat normally due to digestive problems, all nutrition was given through an IV line. Doctors started treatment with the antibiotic cefoperazone/sulbactam, giving 2 grams intravenously every 12 hours for seven days.
On the eighth day of treatment, doctors noticed the patient’s blood wasn’t clotting properly. Blood clotting is controlled by a protein called prothrombin, and doctors measure this with a test called prothrombin time (PT). Normal PT is about 11-13.5 seconds. This patient’s PT jumped to 262.9 seconds—nearly 20 times longer than normal. This is extremely dangerous because blood won’t clot to stop bleeding.
Doctors immediately stopped the antibiotic and gave the patient vitamin K (which helps blood clot) and plasma (the liquid part of blood containing clotting proteins). By day three, the patient’s blood clotting returned to normal. Doctors used a special scoring system to determine if the antibiotic caused the problem, and the score indicated it probably did.
This research matters because it identifies a serious but rare side effect that doctors need to know about. The combination of factors in this case—IV nutrition, digestive problems, and this specific antibiotic—created a dangerous situation. By documenting this case, doctors can watch for similar patterns in other patients and prevent serious bleeding complications
This is a single case report, which is the lowest level of scientific evidence. It documents what happened to one patient, not a pattern across many patients. However, the timing is very clear: the problem started during antibiotic treatment and resolved quickly after stopping it. The doctors used a validated scoring system to assess whether the antibiotic caused the problem. The main limitation is that we can’t know if this would happen to other patients or how common this side effect really is
What the Results Show
The patient’s blood clotting time became severely prolonged during cefoperazone/sulbactam treatment. On day eight of receiving the antibiotic, the patient’s prothrombin time (PT) measured 262.9 seconds, compared to a normal range of 11-13.5 seconds. This represents a roughly 20-fold increase in clotting time, which is life-threatening because blood cannot clot to stop bleeding.
The likely cause was that the antibiotic interfered with vitamin K, which is essential for making clotting proteins. The patient was particularly vulnerable because they were receiving all nutrition through an IV, which may not provide adequate vitamin K, and they had digestive problems that would normally prevent them from absorbing vitamin K from food.
When doctors stopped the antibiotic and gave vitamin K treatment plus plasma transfusion, the patient’s blood clotting improved dramatically. By the third day after stopping the medication, the patient’s PT returned to normal levels. This rapid reversal strongly suggests the antibiotic was responsible for the clotting problem.
The case demonstrates that this antibiotic can cause coagulation dysfunction even at standard doses. The patient received a typical dose of 2 grams every 12 hours, suggesting this isn’t a problem only with overdoses. The severity of the clotting problem—with PT reaching 262.9 seconds—shows this can be an extremely serious adverse reaction, not just a minor side effect. The rapid improvement after stopping the medication indicates the effect is reversible if caught and treated promptly
While cefoperazone/sulbactam is known to potentially affect vitamin K metabolism, this case report documents an unusually severe manifestation of that risk. Previous medical knowledge suggested this antibiotic could cause clotting problems, but this case shows just how extreme the effect can be. The combination with IV nutrition and digestive dysfunction appears to create a particularly high-risk situation that doctors should recognize
This is a single case report involving one patient, so we cannot determine how common this side effect is or whether it would occur in other patients. We don’t know if other patients taking this antibiotic have experienced similar problems but weren’t documented. The patient had multiple medical complications (brain bleed, infection, digestive problems, IV nutrition), so it’s possible other factors contributed. We cannot prove this would happen to everyone taking this antibiotic, only that it happened in this specific situation
The Bottom Line
If you’re prescribed cefoperazone/sulbactam, especially if you have digestive problems or receive IV nutrition, ask your doctor about monitoring your blood clotting. Doctors should check clotting parameters (PT/INR) regularly during treatment. If you’re on this antibiotic long-term, vitamin K supplementation may be considered. This recommendation is based on a single case, so discuss individual risk with your healthcare provider. (Confidence: Low, based on case report evidence)
Doctors prescribing cefoperazone/sulbactam should be aware of this risk, especially for patients with digestive problems, those on IV nutrition, or those at risk for vitamin K deficiency. Patients taking this antibiotic should know the warning signs of bleeding problems (unusual bruising, blood in urine or stool, nosebleeds). This is less relevant for healthy people with normal digestion taking the antibiotic for short periods, though monitoring is still prudent
In this case, the clotting problem developed after 8 days of treatment and reversed within 3 days of stopping the medication and receiving treatment. If this side effect occurs, it appears to develop during the first 1-2 weeks of treatment and resolves quickly once the antibiotic is stopped and vitamin K is given
Frequently Asked Questions
Can antibiotics cause blood clotting problems?
Yes, certain antibiotics including cefoperazone/sulbactam can interfere with vitamin K, which is essential for blood clotting. A 2026 case report documented a patient whose clotting time became dangerously prolonged (262.9 seconds versus normal 11-13.5 seconds) after eight days of this antibiotic treatment.
What are the warning signs of blood clotting problems from antibiotics?
Watch for unusual bruising, blood in urine or stool, nosebleeds, bleeding gums, or excessive bleeding from cuts. If you experience these symptoms while taking cefoperazone/sulbactam, contact your doctor immediately, as the clotting problem can be life-threatening.
Who is at highest risk for clotting problems from this antibiotic?
Patients with digestive problems, those receiving all nutrition through IV lines, or those with vitamin K deficiency appear at higher risk. The documented case involved a patient with gastrointestinal dysfunction on total parenteral nutrition, suggesting this combination increases vulnerability.
How quickly does the clotting problem go away if the antibiotic is stopped?
In the documented case, the patient’s blood clotting returned to normal within three days of stopping cefoperazone/sulbactam and receiving vitamin K treatment. This rapid reversal suggests the effect is not permanent if caught and treated promptly.
Should I take vitamin K if I’m prescribed cefoperazone/sulbactam?
Discuss this with your doctor before starting the antibiotic. While this case report suggests vitamin K may be protective, especially for patients with digestive problems or on IV nutrition, individual risk varies. Your doctor can assess whether supplementation is appropriate for your situation.
Want to Apply This Research?
- If prescribed cefoperazone/sulbactam, track any unusual bleeding signs daily: nosebleeds, blood in urine/stool, unusual bruising, or bleeding gums. Log medication doses and any vitamin K supplementation. Record any lab results for PT/INR clotting tests
- Set daily reminders to take vitamin K supplements if prescribed alongside this antibiotic. Schedule and attend all recommended blood clotting tests. Report any bleeding symptoms to your doctor immediately rather than waiting for your next appointment
- Use the app to log clotting test results when available. Track bleeding symptoms weekly. Set alerts for medication refills and lab appointment reminders. Create a medication interaction log if taking multiple drugs. Share results with your healthcare provider through the app’s health data sharing feature
This case report documents a single patient’s experience and should not be interpreted as proof that all patients taking cefoperazone/sulbactam will experience blood clotting problems. This is a rare side effect. If you are prescribed this antibiotic, do not stop taking it without consulting your doctor. If you experience signs of bleeding (unusual bruising, blood in urine or stool, nosebleeds), contact your healthcare provider immediately. This information is educational and not a substitute for professional medical advice. Always discuss medication risks and benefits with your healthcare provider before starting any antibiotic treatment.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.