Overdose

Mild poisoning
Usually associated with a peak salicylate concentration of less than 300 mg/L (2.2 mmol/L): nausea, vomiting, tinnitus, deafness, lethargy or dizziness.

Moderate poisoning
Usually associated with a salicylate concentration of 300 - 700 mg/L (2.2 - 5.1 mmol/L): dehydration, restlessness, sweating, warm extremities with bounding pulses, increased respiratory rate and hyperventilation. Respiratory alkalosis is often present at lower concentrations; metabolic acidosis may co-exist.

Severe poisoning
Usually associated with a peak salicylate concentration of more than 700 mg/L (5.1 mmol/L): cardiac dysrhythmias, acute non-cardiogenic pulmonary oedema, cerebral oedema, convulsions, confusion, coma, hyperpyrexia, heart failure, renal failure and worsening metabolic and lactic acidosis. Central nervous system features including confusion, disorientation, coma and convulsions are more common in children.

Most adult deaths occur in patients whose concentrations exceed 700 mg/L (5.1 mmol/L) (Chapman and Proudfoot, 1989). Patients are more likely to die if they are aged over 70 years, or if they develop coma, convulsions, confusion, agitation, hyperpyrexia, pulmonary oedema or metabolic acidosis (Chapman and Proudfoot, 1989).

Concentrations of over 900 mg/L (6.4 mmol/L) are associated with very severe toxicity.

• There is variability in response to poisoning with this drug.Ingestion of 1-1.2 g by adults has produced little clinical effect but 500 mg in a 15-year-old girl caused prolonged bradycardia. Survival has been reported after overdose of 3 g 

• There is variability in response to poisoning with this drug. Death has been reported following overdose with 70 mg amlodipine while only mild sinus tachycardia occurred after ingestion of 350 mg amlodipine 

• A 17-year-old female developed profound vasoplegia and cardiovascular collapse following ingestion of up to 550 mg amlodipine. She suffered a period of unresponsiveness after a seizure requiring intubation.

The most serious toxic features are respiratory depression, hypercapnoea, reduced consciousness/coma and airway obstruction, mediated by mu and kappa opioid receptor agonism. The toxic dose is very variable according to individual tolerance. These effects will be potentiated by simultaneous ingestion of other sedatives including alcohol. 

• The primary toxicity of benzodiazepines is CNS depression; the effects are potentially more severe when co-ingested with alcohol and other CNS depressants 

• Patients have recovered from deep coma following ingestion of 500 to 2000 mg of diazepam within 48 hours 

• In adults, ingestion of less than 100 mg/kg ibuprofen is unlikely to result in any symptoms but ingestion of 400 mg/kg or more has been associated with significant toxicity 

• In children,  patients who ingested 114 mg/kg remained asymptomatic, compared to 440 mg/kg for those who developed symptoms. No patient who ingested less than 99 mg/kg developed symptoms 

The most serious toxic features are respiratory depression, hypercapnoea, reduced consciousness/coma and airway obstruction, mediated by mu and kappa opioid receptor agonism. The toxic dose is very variable according to individual tolerance. These effects will be potentiated by simultaneous ingestion of alcohol and other sedative drugs (e.g. benzodiazepines, xylazine); reversibility with naloxone will be limited in these situations. 

• Serious toxicity may occur in patients ingesting more than 150 mg/kg in any 24-hour period

• Rarely, toxicity can occur with ingestions between 75 and 150 mg/kg within any 24-hour period in some patients

• Doses consistently less than 75 mg/kg in any 24 hour period are very unlikely to be toxic, although risk may be increased if this dose is repeatedly ingested over two or more days

• The lowest reported dose associated with convulsions and apnoea in adults is 200 mg. The lowest fatal dose reported in one retrospective study of 114 cases was 5000 mg  

• In children the minimum weight-based dose for respiratory depression was 7.9 mg/kg and for convulsions, 4.8 mg/kg 

The onset and severity of symptoms are dependent on the individual's sensitivity to oral anticoagulants, the severity of the overdose and if applicable the duration of treatment.

Haemorrhage (which may be occult) from any body system is the most prominent feature of overdose. It can occur within 1 to 5 days after ingestion and cause cardiovascular collapse.

• The lowest fatal dose for an adult ingesting citalopram alone was reported to be up to 2800 mg, however, there are cases of full recovery following ingestions up to 5200 mg 

• The largest known ingestion of Sertraline is 13.5 g with recovery reported. Another overdose of 2.5 g sertraline alone resulted in death. Overdosage of 400 mg and 500 mg in two children have resulted in serotonin syndrome 

• Death has been reported after ingestion of 6-12 g of Fluoxetine. Deaths have also been noted on FDA databases after much lower doses (260 and 520 mg)