Application of pharmacokinetic-pharmacodynamic modelling in the management of QT abnormalities after citalopram overdose. Relative toxicity of selective serotonin reuptake inhibitors (SSRIs) in overdose. Comparison of toxicity of acute overdose with citalopram and escitalopram. Tox conundrum 025 – Toxidrome challenge.CCC – Hyperthermia associated toxidromes.Patient who develop severe serotonin toxicity require HDU/ICU care.Symptomatic patients require 12-24 hours of monitoring and supportive care and can be medically cleared once asymptomatic with a normal 12-lead ECG. All other patients require 6 hours of observation and if they are asymptomatic at the end of this time with a normal 12-lead ECG they can be medically cleared.Citalopram (>1000 mg) and escitalopram (>500 mg) requires monitoring for at least 12 hours.Citalopram (>600 mg) and escitalopram (>300mg) requires monitoring for at least 8 hours.Most children can be observed at home unless symptomatic.However, adverse effects are common including increased sedation, orthostatic hypotension and anticholinergic side effects. Chlorpromazine: 25 – 100 mg in 100ml of 0.9% saline over 60 minutes.8mg TDS if there is a positive response after the first dose. Cypoheptadine: Antihistamine with anti-serotonergic effects, can be given orally or via a nasogastric tube.If the patient has severe toxicity aggressive supportive care including cooling, intubation, ventilation and neuromuscular paralysis will be necessary – do not use the specific serotonin antagonists below in this situation. Serotonin toxicity: There maybe a role for serotonin antagonists for mild to moderate serotonin toxicity refractory to benzodiazepines.Overdose with other SSRIs does not warrant activated charcoal as the clinical course is more benign.Giving charcoal has to be weighed against the risk of seizures and aspiration. Alert and cooperative patients who have ingested >600 mg citalopram or >300 mg escitalopram may have 50 g of activated charcoal within 4 hours after overdose.Technically the average QT of 6 leads should be plotted on the nomogram but recent evidence would indicate lead V2 is the most accurate if only one lead is to be used. The QT should be measured on the QT nomogram (not using the Bazett formula in toxicology).If citalopram (>1000 mg) and escitalopram (>500 mg) has been ingested then at least 12 hours of cardiac monitoring is required. Continuous cardiac monitoring is required for citalopram (>600 mg) and escitalopram (>300mg) for at least 8 hours.Screening: 12 lead ECG, BSL, Paracetamol level.diazepam 2.5 – 5 mg every 5 minutes IV until gentle sedation is achieved and a heart rate falls towards 100 beats per minute is considered safe. Titrated doses of benzodiazepines are effective e.g. Agitation and tachycardia: Increasing anxiety, sweating, tremor, tachycardia and mydriasis may herald the onset of seizures.Referral to hospital is only required in a larger ingestion of if they become symptomatic. Children: Ingestion of up to 3 tablets is benign. Minor symptoms are usually present within 4 hours and have resolved within 12 hours. Co-ingestion with other serotonergic agents greatly increases the risk of serotonin toxicity.
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