The Psychiatric Patient in Dental Practice
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Direct answer
Lithium has a narrow therapeutic index, and the NSAIDs you prescribe routinely — ibuprofen, diclofenac — reduce its renal clearance and push levels toward toxicity (tremor, ataxia, confusion, diarrhoea), so paracetamol is the analgesic of choice in lithium patients, with hydration actively maintained after surgery. Tricyclic antidepressants sensitise the patient to circulating catecholamines: use an aspirating technique, limit adrenaline-containing cartridges (commonly to about two of 1:100,000 per visit with monitoring), and never combine MAO inhibitors with pethidine or dextromethorphan. The chronic dry mouth from tricyclics and antipsychotics drives the caries and candidiasis you will actually be treating, and long-term typical antipsychotics (haloperidol and kin) cause tardive dyskinesia — orofacial choreiform movements that defeat denture stability. Consent in acute psychosis is deferred until the patient is stabilised; in the stable patient on treatment, it is ordinary consent, and refusal of care to a psychiatric patient is discrimination, not caution.
What you must remember
- Lithium rules: avoid NSAIDs (and diuretics, ACE inhibitors) which raise lithium levels; prefer paracetamol; ensure fluid intake after extractions, because dehydration concentrates lithium.
- Toxicity signature of lithium: coarse tremor, diarrhoea, vomiting, ataxia, drowsiness, confusion — stop and refer; the dental trigger is often a careless analgesic prescription.
- Tricyclic-adrenaline arithmetic: aspirate and limit to roughly two cartridges of 1:100,000 adrenaline per appointment with cardiovascular monitoring — sustained or accidental intravascular injection is the hazard.
- MAOI absolutes: no pethidine, no dextromethorphan, caution with indirect sympathomimetics — hypertensive and excitatory reactions.
- Xerostomia axis: tricyclics, antipsychotics and some SSRIs reduce saliva — caries, candidiasis and burning mouth follow; treat with fluoride, saliva substitutes, antifungals and diet counselling.
- Tardive dyskinesia: chronic typical antipsychotics produce orofacial dyskinesia — lip smacking, tongue chorea, grimacing — complicating prosthetics and demanding (the examinable pair) differentiation from denture-induced movements.
- Clozapine notes: sialorrhoea (a teaching-point contrast with the dry mouth of other agents) and agranulocytosis requiring blood monitoring.
Lithium, the narrow window
A 45-year-old with bipolar disorder on lithium carbonate needs surgical extraction of a mesioangular third molar. Your prescribing decisions matter as much as your surgery. Analgesia: paracetamol regularly, codeine if needed — the instinctive ibuprofen prescription is the classic error, because prostaglandin inhibition reduces renal lithium excretion, and in a patient already near the therapeutic ceiling, three days of diclofenac can produce tremor, ataxia and confusion. Hydration: post-operative sore mouths drink less; instruct warm fluids and adequate water explicitly, because dehydration also concentrates lithium, and low-salt diets do the same (relevant to patients on "BP diets"). Interaction check with the physician: thiazides, ACE inhibitors and metronidazole can all raise lithium levels — coordinate rather than improvise. Surgical technique stays routine: local anaesthesia with adrenaline is acceptable with aspiration; sedation choices go through the psychiatrist when the patient is on multiple agents. The closing safety net: written advice on lithium toxicity symptoms and a phone number to call, because the patient on lithium meets your prescription again at home.
The same visit is the moment to notice her dry mouth from quetiapine, plan fluoride and saliva substitutes, and ask the questions that build the psychiatric dental history — stability, hospitalisations, who prescribes, who decides when she cannot.
High-yield viva angles
Rank the questions examiners actually ask. First, "which analgesic will you give a patient on lithium?" — paracetamol; quoting the mechanism (reduced renal clearance, toxicity) turns a one-word answer into a pass. Second, "can you use adrenaline in a patient on amitriptyline?" — yes, with aspiration and cartridge limitation; the TCI sensitises receptors, so accidental intravascular adrenaline produces exaggerated hypertension and arrhythmia — the numbers (about two cartridges, 0.04 mg ceiling equivalent) show precision. Third, "the schizophrenic patient on ten years of haloperidol has constant lip and tongue movements — what is it?" — tardive dyskinesia, dose- and duration-related, potentially irreversible; the dental consequence is denture instability, and the management involves the psychiatrist, not a bigger denture. Fourth, the xerostomia cascade — psychotropic polypharmacy makes dry mouth one of the commonest real-world reasons psychiatric patients reach a dentist; management is a protocol (fluoride, substitutes, chlorhexidine, antifungal when candidiasis rides in). Fifth, ethics: "a stable schizophrenic asks for implants" — treat with ordinary standards; "an acutely psychotic patient needs extraction" — defer with the psychiatrist until decision-making capacity returns. The refusal-to-treat reflex remains both unethical and examinable.
Frequently asked questions
Which analgesic is safe in a patient taking lithium?
Paracetamol; NSAIDs such as ibuprofen and diclofenac reduce renal lithium clearance and risk toxicity, as do diuretics and dehydration.
How is adrenaline-containing local anaesthesia handled with tricyclic antidepressants?
Use an aspirating technique, limit to about two cartridges of 1:100,000 with monitoring, since tricyclics sensitise the patient to catecholamines.
What is tardive dyskinesia and why does it matter in dentistry?
Orofacial choreiform movements (lip smacking, tongue protrusion, grimacing) from chronic typical antipsychotics; the movements destabilise dentures and complicate prosthetic treatment.
How is psychotropic-induced xerostomia managed in the dental clinic?
Fluoride (including high-strength toothpaste), saliva substitutes, dietary counselling, chlorhexidine for plaque, and antifungal treatment when candidiasis develops — with a psychiatrist consult about substitution options.
Which drugs must never meet an MAO inhibitor?
Pethidine and dextromethorphan (serotonin and excitatory syndromes), with caution also with indirect sympathomimetics that can trigger hypertensive reactions.