Cilostazole
Contraindicated
Textbook
Increased plasma levels and toxicity of cilostazole.
Should not be administered along with inhibitors of CYP3A4.
Source: KDT 7e · p555
Drug reference
Verapamil
Non-dihydropyridine calcium channel blocker (phenylalkylamine) · Antihypertensive
Also known as Verapamil hydrochloride, Isoptin, Calan, Verelan, Verapil
START
Oral IR 80 mg TID (or SR 120–240 mg/day), titrate; IV SVT 2.5–5 mg over 2 min (monitored)
TYPICAL MAX
480 mg/day oral
STOP IF
High-grade AV block/severe bradycardia, decompensated heart failure, severe hypotension
WATCH
HR/ECG/conduction, BP, heart-failure signs, constipation; avoid with beta-blockers (esp. IV) and in WPW-AF
CDSCO approvedHJan AushadhiNPPA price-controlledATC C08DA01
KDIGO 2024 + manufacturer label
- ONSET
- 1.5h · oral onset
- PEAK
- 1.5h · Cmax (IR)
- t½
- 5h · plasma t½
- DURATION
- 8h · IR effect
EXCRETION
Hepatic CYP3A4; ~70% renal metabolites
route + CYP
INTERACTIONS
12 major
incl. contraindicated
PREGNANCY
Use only if clearly needed — limited data; sometimes used for maternal SVT under monitoring
FDA category + note
Top interactionssee all 12 →
- CilostazoleContraindicatedTextbookKDT 7e · p555
- AzolesSevereTextbookHarrison 22e · p1742
- BucindololSevereTextbookG&G 14e · p275
- CeliprololSevereTextbookG&G 14e · p275
Available in India
16 branded formulations. Look up specific brands in the Drugs workspace.
Jan Aushadhi — generic available at GoI pharmacies
Mechanism
Blocks L-type calcium channels in cardiac (SA/AV node, myocardium) and vascular smooth muscle → slowed AV conduction, negative inotropy/chronotropy and vasodilation; rate control and antianginal/antihypertensive effects.
Indications
Supraventricular tachyarrhythmias / rate control in atrial fibrillationAngina (stable, variant)HypertensionCluster-headache prophylaxis (off-label, common)
Dosing
- Adult
- Oral IR 80–120 mg TID (max 480 mg/day); SR 120–240 mg once–twice daily. IV (SVT): 2.5–5 mg over 2 min, repeat 5–10 mg after 15–30 min if needed (monitored).
- Pediatric
- IV avoided in infants (cardiovascular collapse); oral specialist.
- Renal adjustment
- No major adjustment; caution/monitor in severe impairment.
- Hepatic adjustment
- Reduce dose ~30% (cirrhosis — high first-pass, accumulation).
- Geriatric
- Lower dose; constipation, conduction effects.
- Max dose
- 480 mg/day (oral)
Pharmacokinetics
Onset
Oral 1–2 h; IV 1–5 min
Peak effect
IR 1–2 h
Duration
IR 6–8 h; SR ~24 h
Half-life
~3–7 h (longer with chronic use/hepatic impairment)
Bioavailability
~20–35% (extensive first-pass)
Protein binding
~90%
Metabolism
Hepatic CYP3A4 (active norverapamil); strong CYP3A4 and P-gp inhibitor
Excretion
Renal (~70% as metabolites) and faecal
Contraindications
- Severe LV dysfunction / decompensated heart failure
- 2nd–3rd degree AV block or sick sinus (without pacemaker)
- Atrial fibrillation/flutter with accessory pathway (WPW)
- Severe hypotension/cardiogenic shock
- Concomitant IV beta-blocker; hypersensitivity
Side effects
Common
Constipation (prominent)Headache, dizzinessBradycardiaPeripheral oedemaFlushing/hypotension
Serious
- Severe bradycardia/AV block/asystole (esp. with beta-blockers)
- Worsening heart failure (negative inotropy)
- Severe hypotension
- Hepatotoxicity (rare); gingival hyperplasia
Pregnancy & lactation
Pregnancy
Use only if clearly needed — limited data; sometimes used for maternal SVT under monitoring
Lactation
Small amounts in milk — generally considered compatible with monitoring
Drug interactions
Azoles
Severe
Textbook
Increased plasma levels of verapamil.
Source: Harrison 22e · p1742
Bucindolol
Severe
Textbook
Life-threatening bradyarrhythmias.
Particular caution is indicated.
Source: G&G 14e · p275
Celiprolol
Severe
Textbook
Life-threatening bradyarrhythmias.
Particular caution is indicated.
Source: G&G 14e · p275
Esmolol Hydrochloride
Severe
Textbook
Life-threatening bradyarrhythmias.
Particular caution is indicated.
Source: G&G 14e · p275
Acalabrutinib
Severe
Database
Drug interaction classified as: metabolism
Source: DDInter
Acebutolol
Severe
Database
Life-threatening bradyarrhythmias.
Particular caution is indicated.
Source: DDInter
Alfentanil
Severe
Database
Drug interaction classified as: metabolism
Source: DDInter
Amiodarone
Severe
Database
Increase amiodarone levels.
Source: DDInter
Arbutamine
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Atazanavir
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Atenolol
Severe
Database
Life-threatening bradyarrhythmias.
Particular caution is indicated.
Source: DDInter
Related guidelines
Ask House about Verapamil
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Goodman & Gilman 14e, Harrison 22e, Katzung·Verified: 2026-05-19 · House clinical team·Cockpit curated: 2026-05-19