N-acetylcysteine (NAC)

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Pronunciation: en-a-seet-il-SIS-teen

N-acetylcysteine (NAC) ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: N-acetylcysteine (NAC) ballicule

N-acetylcysteine (NAC) NAC mascot mnemonic cartoon — Visual mnemonic: N-acetylcysteine (NAC) mascot
**“Knack, Ace of assisting”**

What it isGlutathione precursor sold over the counter as a dietary supplement; the same molecule as prescription acetylcysteine.

Why this oneNot FDA-approved for any use: NAC has been an approved drug since 1963, and FDA allows supplement sales under enforcement discretion (2022). Off-label in psychiatry; in trichotillomania 1,200-2,400 mg/d beat placebo, 56% vs 16% much improved (Grant 2009).

What limits itNausea and vomiting at higher doses; oral NAC smells of sulfur.

N-acetylcysteine (NAC) molecular structure (skeletal formula) — Molecular structure: N-acetylcysteine (NAC)

Used for

trichotillomania
contrast nephropathy prophylaxis

Principal riskNausea and vomiting at higher oral doses

Classes and tags

Clinical profile

Therapeutic safety burden2 / 4

Overdose danger2 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Defining liabilityInhaled bronchospasm; oral gastrointestinal intolerance

FDA label

Read the full label on DailyMed ↗

NO BOXED WARNINGS

FDA dosing	Population	Start	Target	Max
Acetaminophen overdose - prevent/lessen hepatic injury (acute ingestion or repeated supratherapeutic ingestion)	Adults and pediatric patients >=5 kg	Loading 150 mg/kg IV over 1 h	then 50 mg/kg over 4 h, then 100 mg/kg over 16 h	300 mg/kg total over 21 h (3 doses)

Renal Undefined

Hepatic Undefined

Total 300 mg/kg over 21 h as 3 doses; consider continued treatment beyond 21 h if acetaminophen still detectable or ALT/AST/INR still rising (massive overdose, coingestants, or preexisting liver disease).

Instructions

IV only; hyperosmolar (2600 mOsmol/L) - dilute in sterile water, 0.45% NaCl, or D5W (0.45% NaCl preferred) before infusion
Reduce total volume for patients <40 kg or requiring fluid restriction to avoid fluid overload
Administer as 3 sequential bags: 150 mg/kg over 1 h, then 50 mg/kg over 4 h, then 100 mg/kg over 16 h

Available strengths

inj 200 mg/mL
sol 10, 20 %
inhaler 100, 200 mg/mL

Cautions

Serious acute hypersensitivity/anaphylactoid reactions (fatal/life-threatening anaphylaxis, hypotension, wheezing, bronchospasm, rash) - most common during the loading dose; stop infusion and treat, may carefully restart after resolution
Monitor asthmatic patients closely
Fluid overload (can cause hyponatremia, seizure, death) - adjust total volume for <40 kg or fluid restriction

Adverse reactions

Rash
Urticaria/facial flushing
Pruritus

Pregnancy Limited human data insufficient to inform risk; delaying treatment of acetaminophen overdose may increase maternal/fetal morbidity and mortality; no adverse developmental effects in animals.

Lactation No data on presence in human milk; nearly completely cleared 30 h after administration; may pump and discard milk for 30 h after dosing.

Cost

N-acetylcysteine (NAC) (NAC)

Strength		#/mo	generic $/unit	CostPlus
200 mg/mL	inj	per unit		not offered

NADAC is a voluntary CMS survey of what retail community pharmacies pay for the drugs they stock. N-acetylcysteine (NAC) is administered under clinical supervision and dispensed outside retail pharmacies, so it rarely appears on surveyed invoices.

Other forms: Acetylcysteine (ACETADOTE)

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Memory aids: interaction avatars

no kinetic interactions

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Self-check

Within what interval is NAC described as fully protective after acetaminophen overdose?
Within eight hours.
Are IV NAC infusion reactions usually true allergy?
No; rate-related anaphylactoid reactions.