QT Interval (QTc) - prolonged QTc is > 450 for men, > 470 for women

Relevance to Psychiatry
Several Psych meds prolong QT interval (see below).  The most notorious are:

Thioridazine (MELLARIL)

Pimozide (ORAP)

Ziprasidone (GEODON)

Tricyclic antidepressants:

Amitriptyline

Amoxapine

Clomipramine

Desipramine

Doxepin

Imipramine

Maprotiline

Nortriptyline

Keep track of QTc, which is QT interval corrected for heart rate.


QTc Prolongation Defined


QT Interval Defined

Think of it as an indicator of how "stretched out" the EKG tracing is.  



QT Prolongation Visualized



Torsades de Pointes - Why QT Prolongation is Dangerous

If QT becomes too prolonged, cardiac conduction is "stretched out" (prolonged, delayed) so much that the heart rhythm goes to Torsades.

Other Psych Meds that Prolong QT Interval (see above for notorious QT prolongers)

Amphetamine (ADDERALL)

Atomoxetine (STRATTERA)

Dextroamphetamine (DEXEDRINE)

Methylphenidate (RITALIN)

Lithium

Clozapine (CLOZARIL)

Chlorpromazine (THORAZINE)

Perphenazine (PROLIXIN)

Haloperidol (HALDOL)

Chloral Hydrate

Fluoxetine (PROZAC)

Paroxetine (PAXIL)

Sertraline (ZOLOFT)

Venlafaxine (EFFEXOR)







 Drugs which can prolong QT Interval -see also www.torsades.org

Cardiovascular

Agents

CNS Agents /

Psychotropics

Anti-Infective

Agents

Miscellaneous

Agents

Cytochrome P450

Inhibitors

Anti-arrhythmics

Amiodarone

(low risk of TdP

compared to other

class III agents such as

sotalol; however

potential for DIs)

Bepridil

Bretylium

Disopyramide

Dofetilide

Flecainide

Ibutilide

Procainamide

Propafenone

Quinidine

Sotalol

Dobutamine

Dopamine

Isradipine

Moexipril/HCTZ

Nicardipine

Norepinephrine



Antibiotics

Cotrimoxazole

Fluoroquinolones

Gatifloxacin

Gemifloxacin

Levofloxacin

Moxifloxacin

Ofloxacin

Macrolides

Azrithromycin

Clarithromycin

Erythromycin 11

Roxithromycin

Azole Antifungals

Fluconazole

Itraconazole

Ketoconazole

Voriconazole

Antimalarials

Chloroquine

Halofantrine

Mefloquine

Quinine

Pentamidine

Alfuzosin

Amantidine

Arsenic trioxide

Cisapride(Special Access)

Cocaine

Cyclosporin

Foscarnet

Hydroxyzine

Indapamide

Methadone

Midodrine

Octreotide

Phenylephrine

Probucol

Pseudoephedrine

Ritodrine

Tacrolimus

Tamoxifen

Tizanidine

Triptans(Recently off QT list)

Vardenafil

Antihistamines

Diphenhydramine

Clemastine

Loratidine

(proposed but no reports)

Withdrawn:

Astemizole & terfenadine

Appetite suppressant

Ephedrine

Fenfluramine

Phentermine

Sibutramine

Bronchodilators

Epinephrine

Isoproterenol

Levalbuterol

Metaproterenol

Salbutamol/albuterol

Salmeterol

Terbutaline

CYP3A4 INHIBITORS - watch for interactions that may prolong QT

amiodarone

Azole antifungals:

Fluconazole

Itraconazole

Ketoconazole

Calcium channel blocker:

Diltiazem

Verapamil

Cimetidine

Ciprofloxacin

Grapefruit juice

HIV: protease inhibitors

Macrolides:

Erythromycin

Clarithromycin

Troleandomycin

(not with Azithromycin)

Methadone

SSRI's:

Fluvoxamine

Norfluoxetine

Nefazodone

Paroxetine

CYP2D6 INHIBITORS  - watch for interactions that may prolong QT

Beta Blockers (BBs)

Haloperidol

Phenothiazines

Quinidine

SSRIs (not citalopram)

Terbinafine

TCAs


CYP1A2 INHIBITORS - watch for interactions that may prolong QT

Fluoroquinolones

Fluvoxamine

Grapefruit juice

AVOID COMBINATIONS of PHENOTHIAZINES with TCAs, BETA BLOCKERS, and ANTICONVULSANTS

Some drugs (eg. erythromycin & amiodarone) prolong the QT Interval AND act as inhibitors to potentially increase levels or QT effects of concomitant medications.

BOLD=major significance (well-documented) REGULAR=low-moderate significance (fewer case reports) ITALIC=minor significance (theoretical, few if any case reports)


Comments

Common ICD-9

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