Vasopressors & Inotropes
High-yield High-alert Verified · Oct 2026Prototype: norepinephrine
Vasopressors & Inotropes are a class of medications used for septic and other distributive shock.
Medical view → mechanisms, drug comparisons and Step 1 pharmacology
Catecholamines and related agents — the drugs that keep perfusion going in shock and cardiac arrest — plus milrinone for the failing heart, oral midodrine for orthostatic hypotension and ephedrine for hypotension during anesthesia.
How it works in the body
The system involved, what goes wrong, and how the drug and body interact.
01 Shock — when perfusion fails
Shock is the state where blood pressure and flow fall so low that organs stop getting the oxygen they need. Blood pressure depends on two things: how hard the vessels squeeze (systemic vascular resistance) and how much blood the heart pumps (cardiac output). Different shocks fail differently — septic shock dilates the vessels; cardiogenic shock weakens the pump.
Vasopressors and inotropes are the emergency levers. They borrow the body’s own fight-or-flight (adrenergic) signaling to squeeze vessels, strengthen the heart, or both — buying time while the underlying cause is treated. The IV agents are titrated to effect, usually in an ICU, and epinephrine and norepinephrine are on the ISMP high-alert list; oral midodrine, used for orthostatic hypotension, is the exception.
02 The adrenergic receptors — which lever each drug pulls
These drugs act on the same adrenergic receptors beta-blockers oppose, but in the opposite direction — they stimulate them. Alpha-1 (α1) receptors on blood vessels cause vasoconstriction (↑ resistance, ↑ BP). Beta-1 (β1) receptors on the heart increase rate and contractility (↑ cardiac output). Beta-2 (β2) relaxes vessels and airways.
Each drug is really a recipe of receptor effects. Norepinephrine (mostly α1, some β1) is the first-line pressor in septic shock — strong squeeze, modest cardiac boost. Phenylephrine is pure α1 (squeeze only). Dobutamine is mostly β1 — a pure inotrope for the failing pump, but it can lower BP. Epinephrine hits α and β hard (arrest, anaphylaxis). Dopamine’s effect shifts with the dose. Knowing the recipe tells you what each drug does and what to watch for. Vasopressin is the non-adrenergic exception: it squeezes vessels through V1 receptors, with no direct boost to heart rate or contractility, and is one of the pressors added to norepinephrine when shock stays hypotensive despite fluids and catecholamines.
Isoproterenol is a nonselective β agonist (β1 + β2) with very little α effect: the heart speeds up and contracts harder, but β2 widens the vessels, so cardiac output rises while mean arterial pressure typically falls. Midodrine is an oral prodrug — its active metabolite, desglymidodrine, is an α1 agonist that tightens arterioles and veins, used by day for orthostatic hypotension rather than shock. Milrinone acts beyond the receptors: it inhibits phosphodiesterase 3 (PDE3) in heart and vascular muscle, so cAMP builds up — stronger contraction in the heart, relaxation in the vessels — without being a β agonist. Ephedrine works two ways: it stimulates α and β receptors directly and also makes sympathetic nerve endings release their own norepinephrine. Heart rate and cardiac output rise, resistance rises variably, and blood pressure usually goes up; given as IV boluses for hypotension during anesthesia, its pressor effect can fade with repeated doses (tachyphylaxis).
03 The catch — a powerful squeeze is dangerous where it leaks
The very vasoconstriction that saves a patient centrally becomes destructive if the drug leaks out of the vein. Extravasation of a vasopressor clamps down the local vessels so hard that the tissue loses its blood supply and can die (necrosis). This is why vasopressors go into a large vein — central access is the method of choice, though in septic shock a peripheral start is suggested rather than delaying for a central line — and why the antidote — phentolamine, an α-blocker injected around the site — must be known.
Systemically, too much α1 squeeze can raise the workload on the heart and cause reflex effects and arrhythmias; too much β1 can cause tachyarrhythmias and ischemia. Every dose is a balance between enough perfusion pressure and too much.
Drug names
Indications
- Septic and other distributive shock (norepinephrine first-line; vasopressin added if hypotension persists, then epinephrine as the next step)
- Cardiogenic shock / decompensated heart failure (dobutamine — inotropic support)
- Cardiac arrest and anaphylaxis (epinephrine); symptomatic hypotension/bradycardia
- Milrinone for short-term IV treatment of acute decompensated heart failure
- Isoproterenol for distributive shock, shock from reduced cardiac output, and bronchospasm during anesthesia (labeled); also used for bradyarrhythmias
- Oral midodrine for symptomatic orthostatic hypotension that impairs daily life despite standard care
- Ephedrine (IV bolus) for clinically important hypotension in the setting of anesthesia
Mechanism of action
Stimulate adrenergic receptors: α1 (vasoconstriction → ↑ SVR/BP), β1 (↑ heart rate & contractility → ↑ cardiac output), and β2 (vasodilation/bronchodilation). Each agent has a distinct receptor profile — norepinephrine α1>β1, phenylephrine pure α1, dobutamine β1, epinephrine α+β, dopamine dose-dependent, isoproterenol nonselective β (β1 + β2) with very low α affinity, midodrine an oral prodrug whose metabolite desglymidodrine is an α1 agonist, and ephedrine a direct α and β agonist that also releases norepinephrine from sympathetic neurons. Vasopressin is non-adrenergic — it constricts vessels through vascular V1 receptors. Milrinone is also non-adrenergic — it inhibits phosphodiesterase 3 in cardiac and vascular muscle, raising cAMP (↑ contractility, vasodilation).
Therapeutic effects — what you'll see working
For the IV agents, success is measured in real time: a rising mean arterial pressure (MAP, usually an initial target of 65 mmHg; 60–65 mmHg in septic shock at ≥ 65 years), better organ perfusion (mentation, urine output, lactate clearing). Doses are titrated continuously — the goal is the lowest dose that restores perfusion.
- ↑ Blood pressure (MAP)
- α1-mediated vasoconstriction raises systemic vascular resistance, restoring the perfusion pressure organs need — titrated to a MAP target (commonly 65 mmHg; 60–65 mmHg in septic shock at ≥ 65 years).
- ↑ Cardiac output
- β1 stimulation (dobutamine, epinephrine, norepinephrine, isoproterenol) increases the heart’s rate and force, moving more blood forward in a failing pump. Milrinone raises contractility through PDE3 inhibition, with a smaller rise in heart rate than the catecholamines, and also lowers wedge pressure and vascular resistance.
- ↑ Standing blood pressure (midodrine)
- Desglymidodrine’s α1 action raises arteriolar and venous tone: standing systolic pressure is about 15–30 mmHg higher 1 hour after a dose, with some effect for 2–3 hours. Supine and sitting pressures rise too, which is the drug’s main hazard.
- Restored organ perfusion
- The end goal — judged by improving mentation, rising urine output, and a falling lactate — signals oxygen is reaching tissues again.
Adverse effects
The adverse effects are the adrenergic drive taken too far — excessive squeeze (ischemia), excessive cardiac stimulation (arrhythmias), and the local disaster of extravasation. Milrinone’s are its cAMP effects taken too far: ventricular arrhythmias and vasodilator hypotension.
Antidote
Interactions
Contraindications
Most are relative — these are emergency drugs — but certain states make excessive vasoconstriction or cardiac stimulation especially hazardous. A few are listed as contraindications: halogenated anesthesia, pheochromocytoma (dopamine), idiopathic hypertrophic subaortic stenosis (dobutamine), tachycardia, ventricular arrhythmias and angina (isoproterenol), and, for oral midodrine, severe heart disease, acute renal disease, urinary retention, pheochromocytoma, thyrotoxicosis and persistent supine hypertension. Milrinone’s only labeled contraindication is hypersensitivity to it, and ephedrine’s label lists none.
When to hold
Assess before giving — these findings mean hold the dose and act.
Nursing considerations
The RN-specific layer — each action paired with the reason it matters.
Common questions
What are Vasopressors & Inotropes used for?
How do Vasopressors & Inotropes work?
What are the serious side effects of Vasopressors & Inotropes?
What is the antidote for Vasopressors & Inotropes toxicity?
When should a nurse hold Vasopressors & Inotropes, and what safety checks apply?
Why are Vasopressors & Inotropes considered high-alert?
Conditions treated
ARDS pulls blood pressure down three ways at once — PEEP cuts preload, deep sedation blunts tone, and sepsis (the leading cause) dilates the circulation — and a failing right ventricle adds a fourth. Vasopressors support cardiac output and tissue perfusion so that lung-protective settings and proning can continue; norepinephrine and epinephrine also raise right-ventricular contractility. They are the reason the conservative fluid strategy waits: FACTT withheld diuresis until the patient held a MAP above 60 mm Hg off vasopressors for 12 hours.
Epinephrine is THE drug of anaphylaxis — given first, immediately on recognition: its alpha-1 vasoconstriction reverses the vasodilation and capillary leak while its beta effects reverse the bronchospasm. Adult dose 0.3–0.5 mg IM (1 mg/mL) in the mid-anterolateral thigh (pediatric 0.01 mg/kg, max 0.5 mg), repeatable every 5–15 minutes (WAO 2020) — about 35% of patients need a second dose. There is no absolute contraindication in anaphylaxis. Refractory cases escalate to a low-dose IV epinephrine infusion in the ICU.
Phenylephrine is the pressor of choice for takotsubo shock with outflow obstruction. Beta-agonists such as dopamine and dobutamine are on the HCM avoid list — added contractility tightens the obstruction.
When crystalloid is not enough, vasopressors may be required for refractory hypotension; cardiac support follows ACLS protocols (StatPearls).
For hypotension after the tumour is removed — rapid volume replacement first, then intravenous vasoconstrictors "(e.g., norepinephrine or phenylephrine)," sometimes for several hours.
Counter the pathologic vasodilation of septic shock when hypotension persists during or after fluids, targeting MAP ≥ 65 mmHg. Norepinephrine is first-line (SSC 2026 accepts norepinephrine or epinephrine first when the heart is also failing); vasopressin is the preferred add-on when norepinephrine is inadequate, epinephrine is used when a further agent is needed or vasopressin is unavailable, and pressors may be started peripherally rather than delayed for central access. For adults aged 65 or older, SSC 2026 suggests a lower initial target of 60–65 mmHg. Septic shock still needing norepinephrine or epinephrine at ≥ 0.25 µg/kg/min at least 4 hours after starting adds IV hydrocortisone 200 mg/day (SSC 2026).
Started when the MAP will not reach target after appropriate fluid resuscitation (in unstable septic shock, SSC 2026 allows starting them alongside the first fluids, case by case) — vasoconstriction (α-1) restores SVR and MAP that fluid alone can’t. Norepinephrine is first-line in septic shock (SSC), preferred over dopamine in cardiogenic shock (fewer arrhythmias), and first choice in neurogenic shock, where its β activity also supports the bradycardic heart (atropine counters the vagal excess). Anaphylaxis is the exception: epinephrine, whose β-2 effect adds bronchodilation — give it IM early; there is no absolute contraindication. Peripheral starts are acceptable while central access is obtained — watch for extravasation.
Hypotension in TRALI and shock — "hemodynamic support with fluid resuscitation or pressors may be necessary." For surveillance reporting, NHSN grades a reaction life-threatening when major intervention such as vasopressors, intubation or ICU transfer is needed.
See also
Slow heart rate & lower BP by blocking β-adrenergic receptors. Watch for bradycardia.
Lower BP by blocking angiotensin conversion. Classic dry cough & angioedema risk.
Lower LDL cholesterol via HMG-CoA reductase inhibition. Monitor for myopathy.
Injectable antibodies that protect the liver’s LDL receptors, cutting LDL cholesterol by about half and lowering cardiovascular events. Given subcutaneously every 2–4 weeks.
PPAR-α agonists that mainly lower triglycerides — used with diet for severe hypertriglyceridemia — with muscle, gallbladder, liver and kidney risks, highest for gemfibrozil combined with a statin.
Non-absorbed resins that trap bile acids in the gut, forcing the liver to use cholesterol and pull LDL from the blood. Constipation, drug binding and rising triglycerides are the issues to manage.
Sources
- Inotropes and Vasopressors — receptor profiles, indications, titration — StatPearls (NCBI)
- Norepinephrine — first-line pressor in septic shock, adverse effects — StatPearls (NCBI)
- LEVOPHED (norepinephrine) — prescribing information — DailyMed (NLM)
- ADRENALIN (epinephrine) — prescribing information — DailyMed (NLM)
- Dopamine HCl Injection — prescribing information — DailyMed (NLM)
- Dobutamine Injection — prescribing information — DailyMed (NLM)
- Phentolamine Mesylate for Injection — extravasation of norepinephrine — DailyMed (NLM)
- Phenylephrine HCl Injection — prescribing information — DailyMed (NLM)
- Drugs@FDA — VAZCULEP (NDA 204300) marketing status — U.S. FDA
- Insights from the 2026 Surviving Sepsis Campaign guidelines (MAP target, peripheral vasopressors) — Acute and Critical Care (PMC)
- Autonomic nervous system — adrenergic agonists (Ch. 4) — Open RN — Nursing Pharmacology
- High alert medications off the radar: a systematic review (ISMP list, Table 6) — PMC (open access)
- Advanced Cardiac Life Support (ACLS) — epinephrine, dopamine — StatPearls (NCBI)
- Septic Shock — perfusion assessment — StatPearls (NCBI)
- VASOSTRICT (vasopressin) — vasodilatory shock despite fluids and catecholamines (FDA label) — DailyMed (NLM)
- Shock — norepinephrine first, vasopressin added if refractory — StatPearls (NCBI Bookshelf)
- Epinephrine — next-step pressor after norepinephrine and vasopressin in septic shock (StatPearls, citing the Surviving Sepsis Campaign) — StatPearls (NCBI Bookshelf)
- Milrinone Lactate Injection (Hospira) — FDA label: PDE3 mechanism, short-term use in acute decompensated HF, arrhythmia warnings, renal dosing — DailyMed (NLM)
- Milrinone — inotropy and lusitropy, chronotropy vs catecholamines, monitoring — StatPearls (NCBI)
- Isoproterenol Hydrochloride Injection (Amphastar) — FDA label: indications, contraindications, interactions — DailyMed (NLM)
- Isoproterenol — β1/β2 effects, bradydysrhythmias, monitoring — StatPearls (NCBI)
- Midodrine Hydrochloride Tablets (Apotex) — FDA label: boxed warning (supine hypertension), prodrug desglymidodrine, dosing-time principle — DailyMed (NLM)
- The use of stems in the selection of INN (2018) — -rinone, -drine — World Health Organization
- Akovaz (ephedrine sulfate) — hypotension during anesthesia; direct α/β agonist and norepinephrine release; tachyphylaxis, oxytocic interaction (FDA label) — FDA / DailyMed
- Emerphed (ephedrine sulfate) — FDA label — FDA / DailyMed
Reviewed by Hae Suk Lee, RN
Educational summary for nursing students. Always verify against current prescribing information and your institution's protocols before administering. Not medical advice.