Correct Answer: C. Lithium
Lithium is a mood stabilizer used in bipolar disorder that causes oral ulceration and stomatitis as a well-documented adverse effect. The patient's presentation of lesions with burning sensation on eating spicy food is classic for drug-induced oral ulcers. Lithium's mechanism involves direct mucosal irritation and altered salivary composition, reducing protective mucin secretion. The burning sensation on spicy food (acidic/irritant stimuli) is pathognomonic for mucosal ulceration. In Indian psychiatric practice, lithium remains a first-line agent for bipolar disorder despite its narrow therapeutic index (0.6–1.2 mEq/L), and oral ulceration is one of the most common early mucosal side effects encountered. The lesions typically appear as painful aphthous ulcers on the buccal mucosa, tongue, or gingiva. Management includes dose reduction, improved oral hygiene, topical corticosteroids, and switching to alternative mood stabilizers (valproate, carbamazepine) if severe. This is a high-yield adverse effect frequently tested in pharmacology exams because it bridges drug toxicity with clinical presentation.
Why the other options are wrong
A. Beta blockers — Beta blockers (propranolol, atenolol) cause dry mouth (xerostomia) and may rarely cause lichenoid reactions, but do NOT cause acute painful oral ulceration with burning sensation on spicy food. Xerostomia presents as dryness without ulcers. This is a distractor that confuses oral side effects of different drug classes. B. Ciprofloxacin — Ciprofloxacin (fluoroquinolone) is known for photosensitivity, tendinitis, and QT prolongation, but NOT for oral ulceration. While some antibiotics (penicillins, sulfonamides) can cause oral ulcers via allergic reactions, ciprofloxacin is not classically associated with this. NBE uses this to test knowledge of antibiotic-specific adverse effects. D. Fluconazole — Fluconazole is an antifungal used for candidiasis, which itself causes oral lesions, but fluconazole does NOT cause drug-induced ulceration. The question stem describes ulceration with burning on spicy food (chemical irritation), not fungal infection. This is a trap for students who confuse oral candidiasis (treated by fluconazole) with drug-induced ulcers.
High-Yield Facts
- Lithium-induced oral ulceration is a direct mucosal toxicity presenting as painful aphthous ulcers on buccal mucosa, tongue, and gingiva.
- Therapeutic range of lithium is 0.6–1.2 mEq/L; toxicity risk increases above 1.5 mEq/L, with oral ulcers appearing at therapeutic doses.
- Mechanism: Lithium reduces salivary mucin secretion and causes direct epithelial irritation, impairing mucosal barrier function.
- Management of lithium-induced ulcers: Dose reduction, topical corticosteroids (triamcinolone), improved oral hygiene, or switch to valproate/carbamazepine.
- Burning sensation on spicy/acidic food is a discriminating sign of mucosal ulceration (not xerostomia or candidiasis).
Mnemonics
LITHIUM ORAL TOXICITY Lesions (ulcers) → Irritation of mucosa → Therapeutic drug → High risk in bipolar patients → Increased salivary loss → Ulceration worsens → Manage with dose reduction PSYCH DRUG ORAL SIDE EFFECTS Lithium = Ulcers; Antipsychotics = Xerostomia; SSRIs = Bruxism. Use when differentiating psychiatric drug toxicities.
NBE Trap
NBE pairs oral ulceration with fluconazole (antifungal) to trap students who confuse drug-induced ulcers with oral candidiasis. The key discriminator is the burning sensation on spicy food—a sign of chemical irritation of ulcerated mucosa, not fungal infection.
Clinical Pearl
In Indian psychiatric clinics, lithium-induced oral ulcers are one of the earliest signs of mucosal toxicity and should prompt serum lithium level estimation. Patients often report worsening symptoms with spicy Indian cuisine (curries, chaat), making this a culturally relevant clinical clue for diagnosis.
_Reference: KD Tripathi Pharmacology Ch. 12 (Mood Stabilizers); Robbins Ch. 9 (Drug-Induced Injury)_