172 Tox icolog y
SPECIFIC POISONS(ii) A potentially toxic ingestion of paracetamol (more than 20 tablets
or 200 mg/kg) in a patient presenting 8– 24 h after overdose, or if
the serum paracetamol level will not be available within 8 h of the
original ingestion:
(a) commence treatment immediately without waiting for the
blood results
(b) cease treatment if the serum paracetamol level turns out to
be below the relevant treatment line, and the ALT and PTI
(INR) are normal.
(iii) Patients presenting with deranged ALT and PTI (INR) more than
24 h after acute overdose, or following staggered overdose
(a) serum paracetamol levels are difficult to interpret in cases
of staggered ingestion. Monitor the PTI (INR) and ALT
regularly instead and seek specialist toxicologist advice (see
below).
4 Consult a clinical toxicologist for patients presenting with a staggered
overdose, with delayed presentation of more than 24 h, and patients with
severe liver dysfunction and an elevated PTI (INR).
5 Use the adult infusion protocol for NAC below.
(i) Take care with the dose calculation. Read from the drug-insert
infusion dosage guide the volume in millilitres of NAC 200 mg/
mL to be added to the 5% dextrose, according to the patient’s
weight:
(a) 150 mg/kg in 5% dextrose 200 mL i.v. over 15 min.
(b) 50 mg/kg in 5% dextrose 500 mL i.v. over 4 h.
(c) 100 mg/kg in 5% dextrose 1000 mL i.v. over 16 h.
6 Side effects are mostly from non-allergic anaphylactic reactions, occurring
in the first 30 min of administering high-dose NAC. These include nausea,
f lushing, itching, urticaria, wheeze and hypotension.
(i) Stop the infusion.
(ii) Give promethazine 12.5–25 mg i.v. and hydrocortisone
200 mg i.v.
(iii) Once symptoms have settled, re-commence the initial infusion at
a slower rate (e.g. 150 mg/kg over 1 h).Salicylates
DIAGNOSIS
1 The clinical features of salicylate toxicity following acute ingestion are dose
related:
(i) Ingested dose <150 mg/kg: usually asymptomatic.
(ii) 150–300 mg/kg: moderate symptoms such as tachypnoea, nausea,
vomiting and tinnitus (salicylism).