Mucolytic + methylxanthine: no clinically significant pharmacokinetic interaction.
Acetylcysteine does not significantly affect theophylline metabolism. Possible additive therapeutic effect (mucolytic + bronchodilator).
No dose adjustment required.
DailyMed/FDA; EMC-UK
Acetylcysteine + nitroglycerin: risk of hypotension and headache when given together.
The Prontuário Terapêutico records the interaction between acetylcysteine and nitroglycerin (hypotension and headache) in the acetylcysteine monograph (5.2.2). The mechanism is vasodilatory potentiation: acetylcysteine is a glutathione precursor and increases nitric oxide availability, reinforcing the vasodilatory and hypotensive effect of nitroglycerin. The combination is clinically relevant mainly in the coronary patient receiving nitrates who takes acetylcysteine (e.g., as a mucolytic), because symptomatic hypotension and headache may occur in the first administrations. The practical guidance is to monitor blood pressure, warn the patient about the risk of headache and dizziness, and, in case of significant hypotension, assess dose spacing or discontinuation of one of the drugs. It is not a major-severity interaction, but requires active clinical vigilance.
Acetylcysteine + nitroglycerin: risk of hypotension and headache — monitor blood pressure during co-administration.
The Prontuário Terapêutico records the interaction between acetylcysteine and nitroglycerin (hypotension and headache) in the acetylcysteine monograph (5.2.2). The mechanism is vasodilatory potentiation — acetylcysteine increases nitric oxide availability, reinforcing the vasodilatory and hypotensive effect of nitroglycerin.
Clinical monitoring of symptoms (headache, dizziness, hypotension) during the first combined administrations.
Symptomatic hypotension, syncope or severe headache after combined intake.
Monitor blood pressure during co-administration; warn the patient about the risk of headache and orthostatic hypotension.
Prontuário Terapêutico do INFARMED (11th ed., 2012) — Acetylcysteine, 5.2.2
NAC can be taken with or without food; only acidic juices partially inactivate the oral solution (not correctly dissolved effervescent tablets).
Do not dilute the oral solution in acidic juices; dissolve the effervescent tablet in water (site monograph).
Site monograph (NAC — do not dilute with acidic juices, inactivation).
Acetylcysteine can be taken with or without food; taking it with food reduces gastrointestinal discomfort.
Take with food if gastric discomfort occurs.
DailyMed/FDA (NIH/NLM) — approved Acetylcysteine label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5558a5f5-e821-473b-7d8a-5d33d09f0586
Alcohol may reduce glutathione levels and counteract the antioxidant effect of acetylcysteine; limit intake.
Limit alcohol intake during treatment.
DailyMed/FDA (NIH/NLM) — approved Acetylcysteine label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5558a5f5-e821-473b-7d8a-5d33d09f0586
NAC is used prophylactically in contrast-induced nephropathy, but evidence is uncertain — caution in renal impairment (adjusted doses).
Dose adjusted to clearance; do not substitute IV hydration with NAC.
EMC-UK — N-acetylcysteine SmPC (IV route, renal precautions).
Inhaled acetylcysteine may trigger bronchospasm, especially in asthmatic patients.
Use with caution; keep a short-acting bronchodilator available.
EMC-UK (MHRA) — approved Acetylcysteine SmPC: https://www.medicines.org.uk/emc/product/2488/smpc
No entry in the annexes; IV NAC is the antidote for paracetamol poisoning — in these emergencies maternal benefit (life-saving) is absolute and treatment must be given without hesitation. Observational data of exposed pregnancies show no malformations. NAC is not teratogenic in animals.
Emergency use without restriction (paracetamol poisoning, contrast prophylaxis); maternal benefit always prevails.
Compatible; antidote doses are valid during breastfeeding.
EMC-UK (MHRA) — Acetylcysteine SmPC: https://www.medicines.org.uk/emc/product/3501/smpc (section 4.6). MHRA — paracetamol overdose treatment guideline.
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Prevention of paracetamol hepatotoxicity (NAPQI neutralised); mucolysis by disulphide breaking.
Cysteine donor: ↑ hepatic glutathione that conjugates NAPQI (paracetamol reactive metabolite) to harmless mercapturate. Mucolytic: breaks disulphide bonds of mucus glycoproteins, reducing viscosity.
Oral: 6–10% (extensive first pass — reason for IV preference in overdose); IV: 100%.
Deacetylation to cysteine; metabolism by hepatic and renal oxidases; renal excretion.
~ 2–6 h (IV; dose-dependent).
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
