SSRI OVERDOSE
SEROTONIN SYNDROME
DANGEROUS DRUGS:
SSRI (especially within 14d of MAOI)
LSD
Lithium
TCA’s
MDMA/Amphetamines
Beware:
Citalopram
Pethidine/fentanyl
Tramadol
Sumatriptan
Tryptophan
St John’s Wort
NB may be caused by OD, Interactions, or therapeutic levels
SYMPTOMS/TOXIDROME:
More rapid than NMS
Usually resolves within 24-48hrs
Criteria:
Must have at least 3 of: altered mental status, agitation, tremor, shivering, diarrhoea,
hyperreflexia, myoclonus, ataxia, or hyperthermia
Other causes (infection, metabolic, other substance use/withdrawal) excluded
Neuroleptics not started prior to onset
EARLY:
Mental – Agitation, Confusion
Neuromuscular – Akathisia, Clonus (espec ocular & lower limb), Hyperreflexia,
ataxia, Repetitive rotation of head
Autonomic – Shivering, Diarrhoea
LATE
Mental - Coma
Neuromuscular - Myoclonus, Rigidity (usually lower limbs “stiff man” synd)
Autonomic – Tachycardia, Mydriasis, Sweating, Hyperthermia, Hyper/Hypotension,
NB: Usually no rhabdo/incr CK
SIGNS OF SEVERITY/WORRYING SIGNS
Rapidly incr temp (>39)
Alt conscious state
COMPLICATIONS
Metabolic acidosis
Rhabdomyolysis
Renal Failure
Seizures
DIC
Compared to NMS
More rapid onset/offset
Ocular clonus
Limb rigidity (usually late & proximal)
Severe rhabdomyolysis rare
Hyperthermia less severe
ECG CHANGES
Nil specific
Co-ingestants may prolong QRS/QT
SPECIFIC INVESTIGATIONS/LEVELS
Nil
Co-ingestants may cause anion gap acidosis
DECONTAMINATION
Activated charcoal of < 1hr
ANTIDOTE
Nil
SPECIFIC TREATMENT
MILD
Symptomatic/supportive
Usually lasts <24hrs
MODERATE
1) Cyproheptadine (5HT2 antag)
8mg o stat, then 4mg 4hrly
2) Phenothiazines
SEVERE
Methysergide
Phenothiazines
Olanzapine 5MG o/IM
Chlorpromazine 50-100mg IM/IV stat then 50-100mg 6hrly
Severe Hyperthermia
Barbituates, Paralysis for intubation/thermal control
THINGS TO AVOID?
Other serotonergic drugs
Dantrolene & Bromocriptine increase serotonin levels
May cause deterioration
DIALYSIS HELPFUL?
Not for decontamination – LARGE Vd
Only for renal failure
ECMO AN OPTION?
Unsure – probably not an option as not a cardiac toxin
INTERACTIONS
SSRI’s INHIBIT cP450, decrease metab and increase levels of:
Warfarin
Clozapine
Digoxin
Phenytoin
Carbamezepine
Barbituates
BZD’s
B-Blockers
Most TCA’s
Caffeine
Some anti-psychotics