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                   530 Chapter 15: Overdose, poisoning and addiction


                   Management                                     before waiting for serum iron levels. Gastrointesti-
                   Activated charcoal may be considered in conscious pa-  nal haemorrhage may require blood replacement and
                   tientswithin1hourofingestionandconsumptionabove  metabolic acidosis should be corrected. Liver and re-
                   120mg/kg.Patientsmayrequireprotectionoftheairway,  nal support may be required.
                   correction of hypoglycaemia and hypokalaemia, and     In absence of symptoms, serum levels are monitored
                   then any metabolic acidosis with intravenous sodium  every 2 hours until levels fall or symptoms develop.
                   bicarbonate.                                   Symptomatic patients with moderate (3–5 mg/L or
                     Haemodialysis is used if plasma salicylate level is 700  55–90 µmol/L) or severe (>5 mg/L or 90 µmol/L)
                   mg/L (5.1 mmol/L), renal or cardiac failure, convulsions  poisoning may require treatment with i.v. desferriox-
                   or if there is severe metabolic acidosis.      amine. Patients who have not developed symptoms
                                                                  by 6 hours following ingestion are unlikely to have
                                                                  had a significant overdose and do not require further
                   Iron overdose                                  monitoring.
                                                                  Within an hour of ingestion of large doses of iron,

                   Definition
                                                                  gastric lavage or endoscopic removal of tablets may be
                   Accidental or deliberate overdose of iron salts.
                                                                  performed.
                   Aetiology
                   Iron poisoning is usually seen in childhood and results  Tricyclic antidepressant overdose
                   from accidental ingestion of iron-containing medica-
                                                                Definition
                   tions such as vitamin preparations mistaken for sweets.
                                                                Accidental or deliberate overdose of tricyclic antidepres-
                                                                sant drugs.
                   Clinical features
                   Iron causes acute necrotising gastritis. Patients may de-
                                                                Incidence/prevalence
                   velop nausea, vomiting, abdominal pain and diarrhoea.
                                                                Almost 1.8% of poisoning cases, but 18% of all deaths
                   In severe poisoning acute upper gastrointestinal bleed-
                                                                by poisoning.
                   ing, convulsions and metabolic acidosis may occur. Late
                   signs in severe overdose include hypotension, coma, hy-
                                                                Pathophysiology
                   poglycaemia and hepatocellular necrosis.
                                                                Tricyclic antidepressants have anticholinergic, alpha-
                                                                adrenergic blocking, and adrenergic uptake inhibiting
                   Investigations                               properties. They also have a quinidine like effect on the
                   Aserum iron level (ideally at 4 hours after ingestion) is  myocardium. Alcohol and other psychotropic drugs in-
                   the best laboratory measure of severity. Abdominal X-  crease the toxicity.
                   raymay show radio-opaque tablets present in the stom-
                   ach or small bowel if taken within 2 hours of ingestion.
                                                                Clinical features
                   Araised neutrophil count and serum glucose suggests
                                                                    Common features include hot, dry skin, dry mouth,
                   toxicity. LFTs and blood gas measurements should be
                                                                  dilated pupils and urinary retention.
                   performed.
                                                                    Cardiovascular consequences include sinus tachycar-
                                                                  dia, vasodilation, hypotension and cardiac arrhyth-
                   Complications                                  mias.
                   Gastrointestinal perforation or infarction.      Neurological consequences include ataxia, nystagmus
                                                                  and altered levels of consciousness including coma,
                   Management                                     hypothermia and respiratory depression. There may
                     In severe poisoning (unconscious or hypotension)  be increased tone, increased deep tendon reflexes and

                     intravenous fluids and desferrioxamine (a chelating  extensor plantar responses. If the patient is comatose,
                     agent for iron) should be commenced immediately  all reflexes may be absent.
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