A 62-year-old man with chronic obstructive pulmonary disease presents with acute exacerbation characterized by increased sputum purulence and dyspnea. Sputum culture is pending. He is started on levofloxacin 750 mg once daily. On day 3 of therapy, he develops acute onset severe left calf pain and swelling with palpable cord. Duplex ultrasound confirms deep vein thrombosis. What is the most appropriate next step in management?

Explanation

## Clinical Scenario Analysis This patient has developed a serious adverse event—deep vein thrombosis (DVT)—temporally associated with fluoroquinolone use. Fluoroquinolones, particularly older agents like levofloxacin, carry a documented risk of thromboembolic complications through mechanisms including platelet aggregation and endothelial dysfunction. ## Management Approach ### Step 1: Recognize the Adverse Event **Key Point:** Fluoroquinolone-associated thromboembolism is a known but underreported adverse effect. The temporal relationship (day 3 of therapy) and confirmed DVT on imaging constitute a drug-related complication. ### Step 2: Discontinue the Offending Agent **High-Yield:** Continuing a fluoroquinolone after thromboembolism has developed is contraindicated. The drug must be withdrawn immediately to prevent further thrombotic events and allow natural fibrinolytic mechanisms to operate. ### Step 3: Initiate Anticoagulation **Clinical Pearl:** DVT is a medical emergency requiring prompt anticoagulation regardless of the underlying cause. Low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH) is the standard first-line agent, followed by transition to warfarin or direct oral anticoagulants (DOACs) for long-term management. ### Step 4: Select Alternative Antibiotic **Key Point:** Switch to a different antibiotic class—beta-lactam (cephalosporin, amoxicillin-clavulanate) or macrolide—that does not carry thrombotic risk. The underlying respiratory infection still requires treatment. ## Why This Approach? | Action | Rationale | |--------|----------| | Discontinue FQ | Remove the causative agent | | Initiate anticoagulation | Prevent clot propagation and PE | | Switch antibiotic class | Treat infection without repeating harm | | Monitor closely | Assess for bleeding, recurrent thrombosis | **Warning:** Continuing the fluoroquinolone while anticoagulating does not address the root cause and risks further thrombotic events.