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A case of acute confusion. Lydia Sudbury. 61 year old lady. Presenting symptoms Agitation Confusion “Hasn’t stopped talking for 4 days”. Recent changes to medications. Mirtazapine increased from 30mg to 45mg Also on: Sertraline 100mg Amitriptyline 100mg. Serotonin syndrome - drugs.
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A case of acute confusion Lydia Sudbury
61 year old lady Presenting symptoms • Agitation • Confusion • “Hasn’t stopped talking for 4 days”
Recent changes to medications • Mirtazapine increased from 30mg to 45mg • Also on: • Sertraline 100mg • Amitriptyline 100mg
Serotonin syndrome - drugs • Antidepressants • SSRI, SNRI, TCA, MAOI, St John's wort, lithium. • Analgesics • tramadol, pethidine, fentanyl, dextromethorphan (in OTC cough remedies). • Antiemetics • ondansetron, metoclopramide. • Recreational • cocaine, MDMA, amphetamine, LSD. • Others • eg, linezolid, tryptophan, buspirone, methylthioninium chloride (methylene blue).
Features • Symptoms usually occur within six hours of taking the provoking drug. • Tremor, akathisia and diarrhoea are early features. • Agitation, hypervigilance and pressured speech may occur. • Acute delirium is a feature of severe cases.
Signs • Autonomic hyperactivity • Hypertension, Tachycardia, Hyperthermia, Hyperactive bowel sounds, Mydriasis, Excessive sweating • Neuromuscular abnormality • Tremor, Clonus, Ocular clonus, Hypertonicity, Hyperreflexia • Mental status changes • Anxiety, Agitation, Confusion, Coma
Investigations • Check U&Es and creatine kinase to look for evidence of rhabdomyolysis and consequent renal impairment. • Toxicology screen, particularly for agents likely to be responsible. • FBC and blood culture/microbiological samples can suggest alternative causes of fever. • LFTs.
Management • Stop the offending agent or interacting drugs. • Activated charcoal if overdose. • Supportive measures such as IV fluids and control of agitation with benzodiazepines.
Complications • Hyperthermia can lead to metabolic acidosis, rhabdomyolysis, acute kidney injury and disseminated intravascular coagulation. • Seizures. • Aspiration pneumonia. • Respiratory failure.
Prevention • Caution in the prescription of serotonergic agents. • All patients starting SSRIs should be counselledabout: • Potential interactions (including OTC and herbal medication). • The symptoms of serotonin toxicity. • Do not prescribe an SSRI together with an MAOI. • Particular care should be taken when changing SSRIs or prescribing more than one antidepressant.
Thanks for listening References: • Patient.co.uk • BNF • The Serotonin Syndrome, The New England Journal of Medicine, Edward W. Boyer and Michael Shannon, 2005;352:1112-20 • GPnotebook • NICE Pathways: Antidepressant treatment in adults (March 2014)