In 2005, CredibleMeds® created a new risk category for drugs, i.e., those with Conditional Risk of torsades de pointes (TdP). This category includes those drugs for which we found strong and convincing evidence of TdP but only under certain clinical conditions and not when used as directed. These conditions included extreme bradycardia, low serum K+ or Mg++, drug overdose or when the drug’s elimination is impaired by another drug (i.e. due to interactions with other prescribed drugs). We also included drugs that have evidence of causing TdP because they create conditions that foster TdP, i.e. drugs that block the elimination of a QT prolonging drug or that cause low serum K+ or Mg++, e.g. certain diuretics.
We have recently reviewed the data now available for the drugs in the Conditional Risk category. We found that the evidence for increased QT or TdP was not convincing for two drugs, amoxapine and protriptyline. Therefore, these drugs will be removed from all lists on the CredibleMeds website and monitored closely.
We found convincing evidence of QT prolongation for clomipramine, desipramine, imipramine, nortriptyline and trimipramine but no convincing evidence of TdP. Therefore, these drugs will be moved from the Conditional Risk list to the Possible Risk list of drugs that have the ability to prolong QT but lack substantial evidence that they cause TdP.
Note that the drugs moved from Conditional Risk to the Possible Risk list will still remain on the list of Drugs to Avoid for patients with congenital LQTS.