Drug Interactions between fluoxetine / olanzapine and papaverine

MONITOR CLOSELY: Intracoronary administration of papaverine has been associated with QT interval prolongation and torsade de pointes (TdP) arrhythmia. The risk may theoretically increase in patients receiving concomitant medications that can also prolong the QT interval or cause bradycardia. QT interval prolongation has not been reported following systemic or intracavernosal administration of papaverine. The precise mechanism of papaverine-induced ventricular tachyarrhythmias has not been delineated, but may involve inhibition of potassium currents and prolongation of the action potential duration. In a study involving 182 consecutive patients undergoing fractional flow reserve measurements, premature ventricular beats occurred in 15.9% of patients following administration of intracoronary papaverine. TdP occurred in 2.8% of patients, and of those, 1.7% developed ventricular fibrillation. The incidence of intracoronary papaverine-induced ventricular tachyarrhythmias has not been determined, but has ranged between <0.67% and 8.8% following intracoronary administration of 6 mg to 20 mg. Based on numerous reports, female gender, hypokalemia, alkalosis, bradycardia, administration of papaverine into the left coronary artery, and a prior history of drug-induced QT prolongation may be risk factors for papaverine-induced fatal ventricular tachyarrhythmias. Apart from isolated case reports, there are no published data regarding the potential interaction between intracoronary papaverine and its use with other QT-prolonging drugs. In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). In addition, the extent of drug-induced QT prolongation is dependent on the particular drugs involved and dosages of the drugs.

MANAGEMENT: Caution and close monitoring are advised during intracoronary administration of papaverine, particularly in patients receiving concomitant drugs that can prolong the QT interval or cause bradycardia and in patients with other risk factors described above. Some QT prolonging medications have specific monitoring, dosing, and/or other recommendations present in their labeling to help mitigate or monitor this side effect; therefore, it may be advisable to consult the package labeling of the concomitant medication if coadministration with intracoronary papaverine is being considered or deemed necessary.

MONITOR CLOSELY: QT interval prolongation and torsade de pointes (TdP) arrhythmia have been associated with intracoronary administration, but not reported following systemic or intracavernosal administration of papaverine. The risk may theoretically increase in patients receiving concomitant medications associated with prolongation of the QT interval. The precise mechanism of papaverine-induced ventricular tachyarrhythmias has not been delineated, but may involve inhibition of potassium currents and prolongation of the action potential duration. The incidence of ventricular tachyarrhythmias has been reported to range between <0.67% and 8.8% following intracoronary administration of papaverine at doses of 6 mg to 20 mg. Female gender, hypokalemia, alkalosis, bradycardia, administration of papaverine into the left coronary artery, and a prior history of drug-induced QT prolongation may be risk factors for papaverine-induced fatal ventricular tachyarrhythmias. Apart from isolated case reports, there are no published data regarding the potential interaction between intracoronary papaverine and its use with other QT-prolonging drugs. In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be affected by the drug and dose of that drug, as well as underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia).

MONITOR CLOSELY: Certain phenothiazines, tricyclic antidepressants (TCAs), and antipsychotic (neuroleptic) agents may potentiate the blood pressure lowering capabilities of papaverine due to their peripheral alpha-1 adrenergic blocking activity. Orthostatic hypotension and syncope associated with vasodilation may occur, particularly during initial dosing and/or parenteral administration of the phenothiazine, TCA, or neuroleptic. The severity of this interaction may be affected by the agent's affinity for the alpha-1 adrenoceptor. One in vitro study demonstrated an affinity for the alpha-1 adrenoceptor for some of these medications that was similar to, or greater than, those of alpha blocker medications used to treat hypertension. Examples of drugs evaluated in this study with a high affinity included amitriptyline, clomipramine, chlorpromazine, clozapine, doxepin, flupenthixol, nortriptyline, paliperidone, quetiapine, risperidone, sertindole, and ziprasidone. On the other hand, examples of those with lower affinities included amisulpride, aripiprazole, lofepramine, protriptyline, and sulpiride.

MANAGEMENT: Caution and close clinical monitoring are advised if papaverine is given with certain phenothiazines, TCAs, and/or antipsychotic (neuroleptic) agents. If papaverine is administered via the intracoronary route, additional monitoring of the QT interval is recommended, particularly in patients with other risk factors (described above). All patients should be closely monitored for the development of hypotension, as this adverse effect is possible regardless of how papaverine is administered. A lower starting dosage and slower titration of the phenothiazine, TCA, or antipsychotic may be appropriate, especially in the elderly. It may also be advisable to use a phenothiazine, TCA, or neuroleptic with a lower affinity for the alpha-1 adrenoceptor when possible. Patients should be counseled to avoid rising abruptly from a sitting or recumbent position and to notify their healthcare provider if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia. Patients should also avoid driving or operating hazardous machinery until they know how the medications affect them.

MONITOR: It is uncertain whether olanzapine causes clinically significant prolongation of the QT interval. In pooled studies of adults as well as pooled studies of adolescents, there were no significant differences between olanzapine and placebo in the proportion of patients experiencing potentially important changes in ECG parameters, including QT, QTcF (Fridericia-corrected), and PR intervals. In clinical trials, clinically meaningful QTc prolongations (QTcF >=500 msec at any time post-baseline in patients with baseline QTcF <500 msec) occurred in 0.1% to 1% of patients treated with olanzapine, with no significant differences in associated cardiac events compared to placebo. Published studies have generally reported no significant effect of olanzapine on QTc interval, although both QTc prolongation and QTc shortening have also been reported. There have been a few isolated case reports of QT prolongation in patients receiving olanzapine. However, causality is difficult to establish due to confounding factors such as concomitant use of drugs that cause QT prolongation and underlying conditions that may predispose to QT prolongation (e.g., hypokalemia, congenital long QT syndrome, preexisting conduction abnormalities).

MANAGEMENT: Some authorities recommend caution when olanzapine is used with drugs that are known to cause QT prolongation. ECG monitoring may be advisable in some cases, such as in patients with a history of cardiac arrhythmias or congenital or family history of long QT syndrome. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.