title: Clarithromycin-nifedipine interaction as possible cause of vasodilatory shock.
abstract: OBJECTIVE
  To report a case of vasodilatory shock possibly resulting from a clarithromycin-nifedipine interaction.
  
  
  METHODS
  A 77-year-old male with uncontrollable hypertension developed shock, heart block, and multiorgan failure 2 days after clarithromycin was added to his antihypertensive treatment (nifedipine, captopril, doxazosin). Invasive monitoring revealed hyperdynamic shock with decreased systemic vascular resistances.
  
  
  CONCLUSIONS
  Nifedipine is metabolized by isoenzyme CYP3A4. This metabolic pathway is inhibited by clarithromycin, thus potentially increasing the plasma nifedipine concentration, which may lead to excessive calcium-channel blocker effects. Clinical manifestations of excessive calcium-channel blockade comprise hypotension or vasodilatory shock and heart block, as in our case. An objective causality assessment revealed that this drug interaction was the possible cause of these adverse effects. Because of an initial diagnosis of septic shock, suspicion of this entity was delayed and specific diagnostic and treatment were not possible.
  
  
  CONCLUSIONS
  This life-threatening clinical picture, including shock and heart block, was possibly the result of a pharmacokinetic interaction between clarithromycin and nifedipine.
authors.affiliation: Service of Anesthesiology, Reanimation and Pain Treatment, Hospital General Universitario de Albacete, Hermanos Falcó, 02006 Albacete, Spain. sergepu@hotmail.com
authors.forename: Manuel
authors.initials: M
authors.lastname: Gerónimo-Pardo
authors.forename: Ana B
authors.initials: AB
authors.lastname: Cuartero-del-Pozo
authors.forename: José M
authors.initials: JM
authors.lastname: Jiménez-Vizuete
authors.forename: Manuel
authors.initials: M
authors.lastname: Cortiñas-Sáez
authors.forename: Ramón
authors.initials: R
authors.lastname: Peyró-García
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000009:adverse effects* / Q000378:metabolism; D000959:Antihypertensive Agents / Q000009:adverse effects* / Q000378:metabolism; D017291:Clarithromycin / Q000009:adverse effects* / Q000378:metabolism; D004357:Drug Synergism; D006327:Heart Block / Q000188:drug therapy; D006801:Humans; D006973:Hypertension / Q000188:drug therapy; D008297:Male; D009543:Nifedipine / Q000009:adverse effects* / Q000378:metabolism; D012769:Shock / Q000139:chemically induced*
chemical_list: D000900:Anti-Bacterial Agents; D000959:Antihypertensive Agents; D017291:Clarithromycin; D009543:Nifedipine