Acetylcysteine

Salts of certain metallic elements such as calcium, iron or gold may reduce the bioavailability of acetylcysteine. In this case it is recommended to administer them after at least 2 hours.

In vitro tests have shown that when cephalosporin antibiotics (tetracyclines, aminoglycosides, penicillins, cephalosporins) and acetylcysteine are mixed, there is a degree of antibiotic inactivation. It is precautionary to advise the administration of oral antibiotics at least two hours before or after acetylcysteine.

Concomitant use of acetylcysteine and carbamazepine may result in sub-therapeutic levels of carbamazepine.

Activated charcoal may reduce the effect of acetylcysteine.

Concurrent administration of nitroglycerin and acetylcysteine causes significant hypotension and leads to temporal artery dilation with possible onset of headache. If concurrent administration of nitroglycerin and acetylcysteine is required, patients should be monitored and warned for hypotension that can be severe and accompanied by a headache.

Animal studies do not indicate direct or indirect harmful effects with respect to reproductive toxicity. As a precautionary measure, it is preferable to avoid the use of acetylcysteine during pregnancy.

There is insufficient information on the excretion of acetylcysteine in human milk. A risk to the newborns/infants cannot be excluded.

No studies on the effects on the ability to drive or use machines have been performed. Acetylcysteine has no known effect on the ability to drive and use machines.

Oral administration

Adverse reactions are listed below, by system organ class and frequency.

Uncommon (≥1/1,000, <1/100), Rare (≥1/10,000, <1/1,000), Very rare (<1/10,000), Not Known.

Immune system disorders

Uncommon: Hypersensitivity

Very rare: Anaphylactic shock, anaphylactic/ anaphylactoid reaction

Nervous system disorders

Uncommon: Headache

Ear and labyrinth disorders

Uncommon: Tinnitus

Cardiac disorders

Uncommon: Tachycardia

Vascular disorders

Uncommon: Hypotension

Very rare: Haemorrhage

Respiratory, thoracic and mediastinal disorders

Rare: Bronchospasm, dyspnoea

Gastrointestinal disorders

Uncommon: Vomiting, diarrhoea, stomatitis, abdominal pain, nausea

Rare: Dyspepsia

Skin and subcutaneous tissue disorders

Uncommon: Urticaria, rash, angioedema, pruritus

General disorders and administration site conditions

Uncommon: Fever

Not Known: Oedema of the face

The occurrence of serious skin reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis have been reported in temporal association with the use of acetylcysteine. In most of these cases reported at least one other drug was administered at the same time, which may have possibly enhanced the described mucocutaneous effects.

In case of recurrence skin and mucosal lesions, medical advice should be sought at once and the use of acetylcysteine terminated immediately.

A decreased blood platelet aggregation in the presence of acetylcysteine has been confirmed by various studies. The clinical relevance has not yet been clarified to date.

IV administration

The most common adverse reactions reported with acetylcysteine are nausea, vomiting, flushing and skin rash.

Less commonly, more serious anaphylactoid reactions have been reported that include angioedema, bronchospasm/respiratory distress, hypotension, tachycardia and hypertension.

Adverse reactions to acetylcysteine usually occur between 15 and 60 minutes after the start of infusion and, in many cases, symptoms are relieved by stopping the infusion. An antihistamine drug may be necessary, and occasionally corticosteroids may be required. Once an adverse reaction is under control, the infusion can normally be restarted at the lowest infusion rate (100mg/kg in 1 litre over 16 hours).

Other reported adverse reactions include: injection site reactions, pruritus, cough, chest tightness or pain, puffy eyes, sweating, malaise, raised temperature, vasodilation, blurred vision, bradycardia, facial or eye pain, syncope, acidosis, thrombocytopenia, respiratory or cardiac arrest, stridor, anxiety, extravasation, arthropathy, arthralgia, deterioration of liver function, generalised seizure, cyanosis, lowered blood urea.

Case reports of fatalities with acetylcysteine have been reported very rarely.

Hypokalaemia and ECG changes have been noted in patients with paracetamol poisoning irrespective of the treatment given. Monitoring of plasma potassium concentration is, therefore, recommended.

If any adverse reactions to acetylcysteine develop, advice should be sought from a National Poisons Centre to ensure that the patient receives adequate treatment of the paracetamol overdose.

Topical instillation into the conjunctival sac

Patient may experience itching, redness and/or irritation in their eye(s).