Clarification of CredibleMeds® TdP Risk Categories

CredibleMeds® Risk Categories for Drugs that Prolong QT and induce Torsades de Pointes (TdP)

Based on ongoing systematic analysis of all available evidence, CredibleMeds® places drugs into broad categories based on whether each can cause QT prolongation or TdP.  Because these actions are highly dependent on the circumstances of each drug’s use AND each patient’s clinical characteristics, we do not attempt to rank-order the drugs within each category.  Therefore, we do not recommend that these lists be used to rank-order the drugs for their relative toxicity.

  Known Risk of TdP - These drugs prolong the QT interval AND are clearly associated with a known risk of TdP, even when taken as recommended.

  Possible Risk of TdP - These drugs can cause QT prolongation BUT currently lack evidence for a risk of TdP when taken as recommended.

  Conditional Risk of TdP - These drugs are associated with TdP BUT only under certain circumstances of their use (e.g. excessive dose, in patients with conditions such as hypokalemia, or when taken with interacting drugs) OR by creating conditions that facilitate or induce TdP (e.g. by inhibiting metabolism of a QT-prolonging drug or by causing an electrolyte disturbance that induces TdP.)

  Drugs to Avoid in Congenital Long QT Syndrome (CLQTS) - These drugs pose a special risk of TdP for patients with CLQTS and include those in the above three categories PLUS additional drugs that do not prolong the QT interval per se but which have a special risk because of their adrenaline-like actions.