<p><strong>Cationic Drugs</strong>: Cationic drugs eliminated by renal tubular secretion: Use with caution.<br />
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<strong>Phenprocoumon</strong>: Metformin may decrease the anticoagulant effect of phenprocoumon. Therefore, close monitoring of the INR is recommended.<br />
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<strong>Levothyroxine</strong>: Levothyroxine can reduce the hypoglycemic effect of metformin. Monitoring of blood glucose levels is recommended, especially when thyroid hormone therapy is initiated or stopped, and the dosage of metformin must be adjusted if necessary.</p>