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NAC (N-Acetyl Cysteine) illustration

NAC (N-Acetyl Cysteine)

A glutathione precursor with strong COPD/respiratory evidence and moderate evidence for OCD-spectrum symptom reduction (as adjunct, not monotherapy).

Aminos Last verified 2026-05-06
stress and mood

What it does

N-Acetyl Cysteine (NAC) at 1 to 2 g/day supports glutathione synthesis. Cochrane 2019 supports use for COPD/chronic-bronchitis exacerbation reduction. OCD-spectrum evidence is heterogeneous: 2024 meta-analysis modestly positive, 2023 Sarris RCT negative.

  • Respiratory mucus clearance / COPD exacerbations Strong evidence

    Mucolytic via disulfide bond cleavage on mucin glycoproteins; reduces COPD/chronic-bronchitis exacerbations at 1200 mg/day. Long prescription history.

    Sources: PMID 31107966

  • OCD symptom reduction (adjunct) Moderate evidence

    Reduces Y-BOCS scores when added to SSRIs in moderate-to-severe OCD; significant benefit between weeks 5 and 8. Effect size modest, evidence mixed (one large 2023 Australian RCT was negative).

    Sources: PMID 39376972

  • Trichotillomania (adults) Moderate evidence

    Grant 2009 (n=50, 1200 to 2400 mg/day, 12 weeks): large reduction in hair-pulling vs placebo (P<.001). Pediatric RCT was NEGATIVE - adult evidence does not transfer to children.

    Sources: PMID 19581567

  • Glutathione precursor Strong evidence

    Provides cysteine (rate-limiting amino acid) for endogenous glutathione synthesis; FDA-approved IV antidote for acetaminophen-induced hepatotoxicity confirms the GSH-replenishment mechanism.

    Sources: PMID 34201323 · N-Acetylcysteine StatPearls monograph

Top picks

  1. 1

    NOW Foods

    NAC 600 mg

    600 mg per cap supports the 1200 to 2400 mg daily protocol.

    Check on Amazon
  2. 2

    Jarrow Formulas

    NAC Sustain 600 mg

    Sustained-release formulation.

    Check on Amazon
  3. 3

    Thorne

    NAC 500 mg / Cysteplus

    Practitioner-channel quality; clean inactives.

    Check on Amazon

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How to use it

Dosage
600 to 2400 mg/day (typical 1200 mg split BID).
Timing
Divided 2x daily. OCD/trich studies titrated 1200 mg/day weeks 1-2 to 2400 mg/day weeks 3+.
With food
Yes
Onset
Respiratory 4 to 12 weeks; OCD/trich 8 to 12 weeks minimum (effect emerges weeks 5 to 8).

What to look for

  • Pure NAC at clinical doses (600 mg per cap), not 'liver support' blends that under-dose.
  • Capsule vs powder: powder cheaper but sulfurous taste; capsules dominate for 1200 to 2400 mg/day compliance.
  • Third-party tested (USP, NSF, Informed Sport).
  • FDA REGULATORY NOTE: since August 2022, FDA exercises enforcement discretion. NAC remains widely sold in US dietary supplements, technically excluded from the supplement definition pending rulemaking.
  • Dose per serving supports 1200 to 2400 mg/day without 6+ pills.

Formats: capsules, powder, effervescent tablets.

Skip if:
  • Nitroglycerin or nitrate medications (MAJOR interaction; severe hypotension via S-nitroso-NAC).
  • Anticoagulants or antiplatelets (warfarin, apixaban, clopidogrel, aspirin) at clinical doses; antiplatelet activity. Stop 2 weeks before elective surgery.
  • Asthma (caution; inhaled NAC can trigger bronchospasm; oral risk lower but documented).
  • Active peptic ulcer or GI bleeding.

FAQ

Why was it briefly hard to find on Amazon?
FDA briefly questioned its supplement-vs-drug status in 2020-2021. Settled in August 2022 with enforcement discretion; now widely available again.
Does it work for OCD as monotherapy?
No. Frame as adjunct to SSRIs. Evidence is heterogeneous and one large 2023 RCT was negative.

Related comparisons

Additional references