PTCB Guide to Antihypertensives

Also called blood pressure medications, including calcium channel blockers and alpha-blockers · suffix -dipine, -zosin · updated August 6, 2026

What gets tested

• Recognizing the stems: -dipine for dihydropyridine calcium channel blockers and -zosin for alpha-1 blockers
• Matching brand to generic: Norvasc is amlodipine, Cardizem is diltiazem, Calan is verapamil, Cardura is doxazosin, Catapres is clonidine
• The split between dihydropyridine and non-dihydropyridine calcium channel blockers and what each does
• Peripheral edema as the classic amlodipine side effect and constipation as the classic verapamil one
• The grapefruit juice interaction with several calcium channel blockers
• Which classes belong to the wider antihypertensive picture, and which drug is which class

What is not tested

You are not asked to select a first line agent, to know target blood pressure numbers, or to titrate therapy. Concentrate on class identification, the stems, brand and generic pairs, and the signature side effects and counseling points. Strengths, dosage forms, routes, special handling, and duration of therapy sit inside PTCE knowledge area 1.4, and combination antihypertensive products make accurate strength reading a practical order entry skill.

Why antihypertensives matter

Amlodipine is among the most dispensed medications in the United States, and blood pressure drugs as a group are the single largest chunk of a typical retail pharmacy's volume. Because so many patients take two or three agents from different classes, and because so many combination products exist, sorting drugs into the right class quickly is one of the most practical skills the Medications domain tests.

Antihypertensives at a glance

Mechanism of action

Blood pressure is the product of how much blood the heart pumps and how tightly the vessels squeeze, so every antihypertensive class works by lowering one of those two. Calcium channel blockers act on the vessels and the heart by blocking L-type calcium channels, which are the route calcium takes into muscle cells to trigger contraction. Less calcium entry means weaker contraction. The class divides by where that effect lands. Dihydropyridines, the drugs ending in -dipine, are selective for the smooth muscle of arteries, so they dilate vessels and lower resistance without much direct effect on the heart. Diltiazem and verapamil are not selective in that way: they also act on cardiac muscle and on the conduction system, so they slow the heart rate and reduce the force of each beat, which is why they are used for rate control in atrial fibrillation as well as for blood pressure. Verapamil has the strongest cardiac effect of the three. Alpha-1 blockers, the -zosin drugs, block the alpha-1 receptors that noradrenaline uses to keep arteries constricted, so the vessels relax. Because those same receptors sit in the prostate and bladder neck, these drugs also relieve urinary symptoms in benign prostatic hyperplasia, which is now their more common use. Clonidine works from the opposite direction, stimulating alpha-2 receptors in the brainstem, which reduces the sympathetic outflow leaving the brain. Hydralazine relaxes arterial smooth muscle directly. Understanding this map matters because the other major classes, covered in their own guides, hit different points again: ACE inhibitors and ARBs act on the renin-angiotensin system, beta-blockers reduce cardiac output and renin release, and diuretics lower blood volume.

Common and important side effects

• Peripheral edema, meaning ankle and lower leg swelling, which is the classic dihydropyridine effect and is dose related
• Constipation, the signature verapamil effect
• Bradycardia and heart block with diltiazem and verapamil, particularly alongside a beta-blocker
• First-dose orthostatic hypotension with alpha-blockers, which can cause fainting, so the first dose is usually taken at bedtime
• Dizziness, flushing, and headache from vasodilation
• Gingival hyperplasia (gum overgrowth) with long-term use of some calcium channel blockers
• Dry mouth and sedation with clonidine, plus severe rebound hypertension if it is stopped abruptly
• Reflex tachycardia with hydralazine, and a lupus-like syndrome with prolonged high doses

Key interactions

• Grapefruit juice inhibits CYP3A4 and raises levels of several calcium channel blockers, notably nifedipine and felodipine
• Verapamil or diltiazem combined with a beta-blocker can cause severe bradycardia or heart block, because both slow conduction
• Verapamil and diltiazem raise levels of simvastatin and lovastatin, increasing the risk of muscle injury
• Alpha-blockers combined with a PDE5 inhibitor such as sildenafil can cause a dangerous drop in blood pressure
• Other blood pressure lowering agents add to the hypotensive effect
• NSAIDs reduce the effectiveness of most antihypertensives

Patient counseling notes

• Take the first dose of an alpha-blocker at bedtime, and rise slowly afterwards, because the first dose can cause marked dizziness or fainting
• Report new or worsening ankle swelling on a -dipine drug, since it is dose related and the prescriber may adjust therapy
• Increase fibre and fluid intake if constipation develops on verapamil
• Do not stop clonidine suddenly, because blood pressure can rebound sharply higher than before treatment
• Avoid grapefruit juice with the calcium channel blockers whose labels warn against it
• Keep dental hygiene appointments, because some calcium channel blockers can cause gum overgrowth
• Do not stop any blood pressure medicine because you feel well: high blood pressure usually has no symptoms

Practice questions

Work the Antihypertensives questions below first, then widen out. Two skills carry most of the Medications domain, and each has its own quiz. The first is drug class identification: recognising which class a drug belongs to from its name or its stem, which is what the drug class identification quiz drills across every class. The second is brand and generic recall, because the exam switches between the two names freely and expects you to follow. Pair this guide with the brand and generic quiz until the brand and generic pairs in the table above come back without effort.

Related drug-class guides

Official sources

• MedlinePlus: Amlodipine
• MedlinePlus: Diltiazem
• MedlinePlus: Verapamil
• MedlinePlus: Doxazosin
• MedlinePlus: Clonidine
• ClinCalc DrugStats: Amlodipine (dispensing data)

PTCB Quiz Prep is an independent study resource, not affiliated with the Pharmacy Technician Certification Board. This guide is for exam preparation, not medical advice. Part of the PTCB Medications domain.