Retroperitoneal haematoma in a patient treated with acenocoumarol, phenytoin and paroxetine.
Coumarin anticoagulants must be strictly monitored because of their narrow therapeutic index and their potential interactions with other drugs. The high probability of interactions can be explained by two pharmacokinetic properties of coumarins: high binding to plasma albumin (99%), being displaced by other drugs with greater affinity to this protein, and metabolism by liver microsomal enzymes (cytochrome P450), which can be induced or inhibited by other compounds (Shinn & Shrewsbury 1985). A case is reported of a clinically relevant drug interaction of phenytoin and acenocoumarol, possibly potentiated by concomitant treatment with paroxetine, leading to a retroperitoneal haematoma.
Department of Clinical Pharmacology, Hospital La Paz, Paseo de la Castellana, Madrid, Spain.
F
F
Abad-Santos
A J
AJ
Carcas
C
C
F-Capitán
J
J
Frias
D000074:Acenocoumarol / Q000008:administration & dosage / Q000009:adverse effects*; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage / Q000009:adverse effects*; D000927:Anticonvulsants / Q000009:adverse effects*; D018687:Antidepressive Agents, Second-Generation / Q000009:adverse effects*; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D005260:Female; D006406:Hematoma / Q000139:chemically induced*; D006801:Humans; D017374:Paroxetine / Q000008:administration & dosage / Q000009:adverse effects*; D010672:Phenytoin / Q000009:adverse effects*; D012187:Retroperitoneal Space
D000925:Anticoagulants; D000927:Anticonvulsants; D018687:Antidepressive Agents, Second-Generation; D017374:Paroxetine; D010672:Phenytoin; D000074:Acenocoumarol