Non-dihydropyridine calcium channel blockers

They block L-type (slow) calcium channels in the heart as well as in arterioles. The SA and AV nodes depend on calcium entry for their electrical activity, so the heart rate and AV conduction slow; heart muscle contracts less forcefully; and widened arterioles lower blood pressure and the heart's workload.

• VerapamilConstipation is its best-known side effect; the NHS notes that specialists also use it to prevent cluster headaches.
• DiltiazemThe NHS also lists it for Raynaud's phenomenon and, as a cream or ointment, for healing anal fissures.

• High blood pressure
• Angina
• Slowing a fast heart rate in atrial fibrillation or flutter
• Preventing or ending supraventricular tachycardia

• ConstipationKnown for
• Slow heart rate (bradycardia)Known for
• Heart block (slowed AV conduction)Known forSerious
• Worsening heart failureSerious
• Low blood pressure
• Dizziness
• Headache
• Ankle swelling (edema)
• Flushing
• Liver injury, from raised enzymes to hepatitis (rare)Serious

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

• Contraindicated in sick sinus syndrome and in 2nd- or 3rd-degree AV block unless a pacemaker works, and in marked hypotension.
• With a beta blocker the slowing adds up: severe bradycardia, heart block or heart failure can follow.
• Atrial fibrillation or flutter with an accessory pathway (WPW): they can speed the ventricles dangerously.
• They raise levels of CYP3A4 substrates such as simvastatin, lovastatin, carbamazepine and ciclosporin.

Written for biofideX in plain words, after checking these references:

• Calcium Channel Blocker (NCI Thesaurus)
• Verapamil hydrochloride tablets: label (DailyMed)
• Diltiazem hydrochloride extended-release capsules: label (DailyMed)
• Diltiazem hydrochloride injection: label (DailyMed)
• Verapamil (NHS)

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.