3 Clinical psychopharmacology3.4 Therapeutics
3.4.5.2 The elderly
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Written by Resident Doctor Committee · Published
Pharmacokinetics in old age
Less body water and more fat raise levels of water-soluble drugs and let lipophilic drugs such as diazepam persist longer.
Low albumin from illness or malnutrition raises the free fraction of highly bound drugs.
Hepatic oxidation falls more than glucuronidation: diazepam forms long-lived active metabolites, while lorazepam and oxazepam form inactive conjugates.
Renal function varies widely, and low muscle mass makes creatinine-based estimates misleading.
Drugs that cause delirium
Drug | Mechanism | Result |
|---|---|---|
Diazepam | Active metabolite desmethyldiazepam accumulates over days as hepatic oxidation slows | Sedative, fluctuating delirium |
Pethidine | Renally cleared metabolite norpethidine accumulates and excites the central nervous system | Higher delirium risk than other opioids; myoclonus, seizures |
Anticholinergic combinations | Reduced cholinergic reserve | Retention, constipation, blurred vision, delirium |
New fluctuating confusion needs delirium assessment for medicines, withdrawal, infection, pain, urinary retention, constipation and metabolic causes.
Restraint is used only once de-escalation has failed in an agitated, confused older inpatient who poses a risk.
Restraint, physical or pharmacological, is the least restrictive option for the shortest time, with frequent review of physical state.
Glycopyrronium
Glycopyrronium bromide is a quaternary ammonium antimuscarinic that reduces mucosal secretions and relaxes smooth muscle.
Its charged structure keeps it out of the brain.
Herbal and complementary treatments
Treatment | Use and evidence | Harm |
|---|---|---|
St John's wort | Hyperforin induces cytochrome P450 enzymes CYP3A4 and CYP2C9 and P-glycoprotein, in liver and gut | Faster warfarin clearance lowers the international normalised ratio (INR); less digoxin absorption lowers its level |
Ginkgo biloba | Leaf extract taken for memory; no consistent benefit in dementia or mild cognitive impairment | Antiplatelet effect adds to bleeding risk with clopidogrel, aspirin or warfarin |
Aromatherapy | Lavender or lemon balm oil by massage or diffuser for distressed behaviour in dementia | A Cochrane review found trial evidence too weak to draw conclusions |
Cumulative burden and review
Burden | Contributors |
|---|---|
Anticholinergic | Psychotropics, bladder antimuscarinics, sedating antihistamines |
Sedative | Hypnotics, opioids, gabapentinoids, antipsychotics |
Hypotensive | Antihypertensives, diuretics, alpha blockers, trazodone |
QT prolonging | Selected antipsychotics, citalopram; bradycardia adds risk |
The Beers Criteria identify medicines likely to do more harm than good in adults aged 65 and over.
STOPP/START criteria prompt review of inappropriate or omitted treatment; both tools support individual judgement.
Reconcile records against what the patient actually takes at every transfer of care.
Prescribing principles
Start low and titrate in smaller steps, allowing for delayed accumulation; "half the adult dose" is not a universal rule.
Do not undertreat serious illness: electroconvulsive therapy may suit selected severe depression.
Dementia or an unwise choice does not by itself remove capacity.
Covert medication needs a lawful, documented, medicine-specific decision, pharmacy advice and regular review.
Visual loss can cause Charles Bonnet hallucinations, often with insight.