Geriatric MedicineTier 2Disease (DEADMAN)

Substance use disorders - overdose

Description

Substance overdose in older patients differs from younger populations in presentation, risk factors, and management complexity - often less clearly linked to recreational use and more often related to prescribed medication, cognitive impairment, or unintentional misuse

Benzodiazepine and opioid prescribing is more common in older adults (for anxiety, insomnia, chronic pain), creating a larger population at risk of prescribed-drug overdose compared with illicit substance overdose, which is comparatively less common in this age group

Reduced physiological reserve and altered pharmacokinetics (see pharmacological changes in ageing) mean a dose tolerated for years can become toxic as renal/hepatic clearance declines, or when a new interacting drug is added - overdose can occur without any change in the patient's own dosing behaviour
Cognitive impairment increases the risk of unintentional double-dosing or medication confusion, distinct from deliberate overdose

Presentation can be atypical - confusion, falls, or reduced consciousness rather than the more obvious presentation seen in younger patients, and may be misattributed to an unrelated acute illness or to dementia progression rather than recognised as a drug effect
A detailed, accurate medication history (including OTC and complementary products, and confirmation of actual versus intended dosing) is essential and often requires collateral history from family/carers or a dosette box/pharmacy review, since self-report can be unreliable

Standard overdose management applies (supportive care, specific antidotes where available - e.g. naloxone for opioid toxicity, flumazenil used cautiously given seizure risk in benzodiazepine-dependent patients) but with lower thresholds for monitoring given reduced physiological reserve
Following recovery, review the circumstances (accidental vs deliberate, medication complexity, cognitive capacity to safely self-administer medications) to prevent recurrence - a dosette box, pharmacy-administered dosing, or medication regimen simplification may be needed rather than simply resuming the same regimen unchanged

Polypharmacy, cognitive impairment affecting safe self-medication, chronic opioid/benzodiazepine prescribing, depression/suicidality (deliberate overdose risk, which should always be considered and asked about directly)

An overdose in an older patient - even one that appears clearly accidental - should prompt a systematic review of medication safety and cognitive capacity for self-administration, since the underlying vulnerability (not just the acute event) is what determines recurrence risk

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