Doctors reported a case where a patient taking cefoperazone/sulbactam, a common antibiotic used to treat bacterial infections like pneumonia, developed serious blood clotting problems after 23 days of treatment. The patient’s blood took much longer than normal to clot, which could be dangerous. When doctors gave the patient vitamin K (a nutrient that helps blood clot), the clotting improved dramatically within two days. This case suggests that people taking this antibiotic for long periods should be monitored carefully for bleeding problems, especially those already at higher risk of bleeding complications.

The Quick Take

  • What they studied: Whether a specific antibiotic (cefoperazone/sulbactam) can cause dangerous blood clotting problems in patients taking it for extended periods
  • Who participated: One patient hospitalized with bacterial pneumonia who received the antibiotic for 23 consecutive days
  • Key finding: The patient developed severe blood clotting delays after three weeks of antibiotic treatment. When given vitamin K, clotting times improved by 61-88% within two days, suggesting the antibiotic interfered with the body’s ability to use vitamin K properly
  • What it means for you: If you’re prescribed this antibiotic for more than a few weeks, ask your doctor about monitoring your blood clotting ability. This is especially important if you already have bleeding concerns or take blood thinners. However, this is based on one case, so don’t stop taking prescribed antibiotics without talking to your doctor first

The Research Details

This is a case report, which means doctors documented what happened with one specific patient. The patient came to the hospital with a lung infection caused by bacteria and was given cefoperazone/sulbactam through an IV (intravenous) line at a dose of 1.5 grams every 8 hours. The doctors carefully tracked what happened to the patient’s blood clotting ability throughout the treatment and after.

On day 26 of treatment (three days after the antibiotic was stopped), the patient developed serious problems with blood clotting—the blood was taking much longer than normal to clot. The doctors tested the patient’s blood using standard clotting tests and found major problems. They then gave the patient vitamin K1 (a nutrient essential for blood clotting) and monitored what happened next.

The doctors used something called the Naranjo assessment score to determine how likely it was that the antibiotic caused the problem. A score of 5 suggests a “probable” connection between the drug and the side effect.

Case reports are important because they alert doctors to rare or unexpected side effects that might not show up in larger studies. While one case isn’t proof that something always happens, it’s a warning sign that doctors should watch for. This helps protect other patients from the same problem.

This is a single case report, which is the lowest level of scientific evidence. It describes what happened to one person, not a large group. We cannot assume this will happen to everyone taking this antibiotic. However, the timing (symptoms appeared after extended use and improved with vitamin K) and the strong improvement after treatment suggest a real connection. The Naranjo score of 5 indicates a probable relationship between the drug and the side effect, which adds some credibility to the observation.

What the Results Show

The patient took cefoperazone/sulbactam for 23 days to treat pneumonia. Three days after stopping the antibiotic, the patient developed severe blood clotting problems. Medical tests showed that blood was taking much longer to clot than it should—specifically, the prothrombin time (a measure of how long blood takes to clot) was very prolonged.

When doctors gave the patient vitamin K1, the improvement was dramatic. Within two days, the prothrombin time decreased by 88.4%, the activated partial thromboplastin time (another clotting test) decreased by 61.1%, and the international normalized ratio (a standard measure of clotting ability) decreased by 88.5%. All of these improvements mean the blood was clotting much better.

The doctors believe the antibiotic interfered with how the body uses vitamin K, which is essential for making proteins that help blood clot. By giving vitamin K directly, they were able to restore the body’s clotting ability quickly.

The case report notes that the patient was at particular risk because of the long duration of antibiotic use (23 days is longer than typical courses). The delayed appearance of symptoms (three days after stopping the medication) is also notable and suggests the antibiotic’s effects lingered in the body even after treatment ended.

While cefoperazone/sulbactam is a commonly used antibiotic, serious blood clotting problems from this drug appear to be rare. Other antibiotics in the same family (cephalosporins) have occasionally been reported to cause similar problems, but this specific combination appears uncommon enough that doctors may not always think to monitor for it. This case adds to a small body of literature suggesting that extended use of this antibiotic warrants caution.

This report describes only one patient, so we cannot say how often this problem occurs or who is most at risk. We don’t know if this patient had other health conditions or took other medications that might have contributed to the problem. Different people may respond differently to the same antibiotic. The case doesn’t tell us the exact dose at which problems are likely to occur or how long someone needs to take the drug before problems develop. More research with larger groups of patients would be needed to fully understand this risk.

The Bottom Line

If you’re prescribed cefoperazone/sulbactam for more than one to two weeks, discuss with your doctor whether blood clotting tests should be done, especially if you have risk factors for bleeding problems or take blood thinners. This recommendation is based on limited evidence (one case), so it should be considered a precaution rather than a definite requirement. Do not stop taking prescribed antibiotics without medical guidance.

People taking cefoperazone/sulbactam for extended periods (more than 2-3 weeks) should be aware of this potential risk. This is especially important for those who already have bleeding disorders, take blood-thinning medications, have liver disease, or are elderly. Healthcare providers prescribing this antibiotic for long-term use should consider monitoring. People taking this antibiotic for typical short courses (5-10 days) have less reason for concern based on current evidence.

In this case, symptoms appeared around day 26 (three days after stopping the 23-day course). If problems do occur, vitamin K treatment appears to work quickly, with major improvements seen within 48 hours. However, this timeline is based on one case and may vary.

Want to Apply This Research?

  • If prescribed cefoperazone/sulbactam for more than two weeks, track any signs of unusual bleeding or bruising daily (nosebleeds, bleeding gums, unusual bruises, blood in urine or stool). Note the date you started the antibiotic and any symptoms that develop.
  • Set a reminder to discuss blood clotting monitoring with your doctor if prescribed this antibiotic for extended use. Ask specifically about vitamin K levels and whether blood tests should be done. Keep a log of any bleeding symptoms to share with your healthcare provider.
  • For patients on extended courses of this antibiotic, establish a baseline by checking in with your doctor about clotting risk factors. During treatment, monitor daily for bleeding signs. After treatment ends, continue monitoring for at least one week, since symptoms in this case appeared after the medication was stopped. Report any concerning symptoms immediately to your healthcare provider.

This case report describes one patient’s experience and should not be interpreted as proof that all patients taking cefoperazone/sulbactam will develop blood clotting problems. Always take medications exactly as prescribed by your doctor. If you experience unusual bleeding, bruising, or other concerning symptoms while taking any antibiotic, contact your healthcare provider immediately. Do not stop taking prescribed medications without medical guidance. This information is educational and should not replace professional medical advice, diagnosis, or treatment. Consult with your healthcare provider about your individual risk factors and whether monitoring is appropriate for your situation.