Bendroflumethiazide
Contraindicated
Textbook
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: G&G 14e · p567
Drug reference
quinidine
Na+ Channel Blocker (Class IA), K+ Channel Blocker, α-Adrenergic Blocker, Vagolytic · Antiarrhythmic
Na+ Channel Blocker (Class IA), K+ Channel Blocker, α-Adrenergic Blocker, VagolyticAntiarrhythmicATC C01BA01
CDSCO approvedATC C01BA01
EXCRETION
—
not curated
INTERACTIONS
12 major
incl. contraindicated
PREGNANCY
X
FDA category + note
Top interactionssee all 12 →
- BendroflumethiazideContraindicatedTextbookG&G 14e · p567
- ChlorthalidoneContraindicatedTextbookG&G 14e · p567
- HydrochlorothiazideContraindicatedTextbookG&G 14e · p567
- HydroflumethiazideContraindicatedTextbookG&G 14e · p567
Mechanism
Quinidine blocks Na+ current and multiple cardiac K+ currents (IKr, IKs, IK1, ITO, L-type Ca2+). It is an open-state blocker of Na+ channels. Its Na+ channel–blocking properties increase threshold for excitability and decrease automaticity. As a K+ channel blocker, it prolongs action potentials (most prominently at slow heart rates). Quinidine also produces α adrenergic receptor blockade and vagal inhibition.
Indications
Maintaining sinus rhythm in atrial flutterMaintaining sinus rhythm in atrial fibrillationPrevent recurrence of ventricular tachycardiaPrevent recurrence of ventricular fibrillationPreventing recurrent ventricular fibrillation in Brugada syndromePreventing recurrent ventricular fibrillation in short QT syndromeparenteral treatment of severe illness due to drug-resistant strains of p. falciparumcombined with tetracycline, doxycycline, or clindamycinMaintenance of sinus rhythm after termination of atrial fibrillation (AF)Maintenance of sinus rhythm after termination of atrial flutter (AFl)
Dosing
- Adult
- 324–648 mg (gluconate) q8h; 200–400 mg (sulfate) q6h.
- Pediatric
- Same as adult
Pharmacokinetics
Half-life
4–10 h
Bioavailability
Well absorbed
Protein binding
~80% (to plasma proteins, including albumin and α1-acid glycoprotein)
Metabolism
Extensive hepatic oxidative metabolism (one active metabolite: 3-hydroxyquinidine)
Contraindications
- Diarrhea
- Prolonged QT interval
- hypersensitivity
- history of blackwater fever
- thrombocytopenic purpura
- thrombocytopenia associated with quinine/quinidine use
- many cardiac conduction defects and arrhythmias
- myasthenia gravis
- optic neuritis
Side effects
Common
Diarrhea (30% to 50% of patients)Headache (cinchonism)Tinnitus (cinchonism)Flushing (cinchonism)Blurred vision (cinchonism)Dizziness (cinchonism)cinchonismtachycardiaprolongation of qrs and qtc intervalsflattening of t wavehypoglycemiahypotensioncramps (as idiosyncrasy)diarrhoea (as idiosyncrasy)purpura (as idiosyncrasy)asthma (as idiosyncrasy)vascular collapse (as idiosyncrasy)Fall in blood pressureDecreased skeletal muscle contractilityAugmented uterine contractionsVomitingDiarrhoeaRinging in ears (Cinchonism)Vertigo (Cinchonism)Deafness (Cinchonism)Visual disturbances (Cinchonism)Mental changes (Cinchonism)Increased P-R intervalIncreased Q-T intervalBroadened QRS complexChanges in T wave shapecinchonism (tinnitus, high-tone deafness, headache, dysphoria, nausea, vomiting, abdominal pain, visual disturbances, postural hypotension)hyperinsulinemia
Serious
- Marked QT interval prolongation (up to 25%)
- Torsades de pointes (2% to 8% incidence, can occur at therapeutic/subtherapeutic concentrations)
- Immune thrombocytopenia (~1%)
- Hepatitis (rare)
- Bone marrow depression (rare)
- Lupus syndrome (rare)
- Ventricular tachycardia (at very high plasma concentrations)
- Marked hypotension (with intravenous use)
- Sinus tachycardia (with intravenous use)
- ventricular arrhythmias
- more cardiotoxic than quinine
- Torsades de pointes
- Sudden cardiac arrest
- Ventricular fibrillation (VF)
- Idiosyncratic angioedema
- Vascular collapse
- Thrombocytopenia
- deafness
- hemolytic anemia
- arrhythmias
- hypotension
Pregnancy & lactation
Pregnancy
X
Drug interactions
Chlorthalidone
Contraindicated
Textbook
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: G&G 14e · p567
Hydrochlorothiazide
Contraindicated
Textbook
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: G&G 14e · p567
Hydroflumethiazide
Contraindicated
Textbook
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: G&G 14e · p567
Indapamide
Contraindicated
Textbook
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: G&G 14e · p567
Metolazone
Contraindicated
Textbook
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: G&G 14e · p567
Trichlormethiazide
Contraindicated
Textbook
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: G&G 14e · p567
Xipamide
Contraindicated
Textbook
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: G&G 14e · p567
Amisulpride
Contraindicated
Database
Increased risk of Torsades de Pointes (TdP) and other ventricular arrhythmias
Concomitant use is contraindicated. Avoid combination.
Source: DDInter
Domperidone
Contraindicated
Database
Increased risk of QT prolongation and Torsades de Pointes (TdP)
Concomitant use is contraindicated. Avoid co-administration.
Lidocaine
Severe
Textbook-cited
Exaggerated cardiac depression; may precipitate arrhythmias
Avoid concurrent use
Source: KDT 7e · p950
Quinolones
Severe
Textbook
Increased risk of QT interval prolongation and torsades de pointes arrhythmias.
Quinolones should be used with caution in patients on class IA antiarrhythmics.
Source: G&G 14e · p1144
Related guidelines
Ask House about quinidine
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Goodman & Gilman 14e, Harrison 22e·Verified: 2026-05-10 · House clinical team