5.2 Neurology, Psychiatry & Gastroenterology
Key Takeaways
- Selective serotonin reuptake inhibitors (SSRIs) are first-line for major depressive disorder and most anxiety disorders; antidepressant onset of full benefit typically takes several weeks, and abrupt discontinuation of short-half-life agents can cause discontinuation syndrome.
- Lithium and certain anticonvulsants are mood stabilizers for bipolar disorder; lithium has a narrow therapeutic index requiring level monitoring and is sensitive to dehydration, NSAIDs, and renal changes.
- Antipsychotics treat schizophrenia; first-generation agents carry higher extrapyramidal risk, while many second-generation agents carry higher metabolic risk requiring weight, glucose, and lipid monitoring.
- Levodopa-carbidopa is the most effective Parkinson disease symptomatic therapy; carbidopa blocks peripheral conversion to reduce nausea and increase central availability.
- Proton pump inhibitors are first-line for erosive GERD and peptic ulcer disease; H. pylori-associated ulcers require eradication therapy, and inflammatory bowel disease management differs by disease type and severity.
Why These Systems Cluster Together
Neurologic, psychiatric, and gastrointestinal drugs share three exam themes: delayed or titrated onset, distinctive monitoring parameters, and clinically important interactions. The NAPLEX repeatedly checks whether you can pick first-line therapy for a presentation, anticipate an adverse effect, and counsel the patient accurately.
Psychiatric Pharmacotherapy
Depression and Anxiety
Selective serotonin reuptake inhibitors (SSRIs) are first-line for major depressive disorder (MDD) and most anxiety disorders because of their tolerability and safety in overdose relative to older agents. Core counseling and safety points:
- Full antidepressant benefit usually takes several weeks; set expectations to support adherence.
- Excessive serotonergic combinations (e.g., adding another strong serotonergic agent) can precipitate serotonin syndrome (mental status changes, autonomic instability, neuromuscular hyperactivity).
- Abruptly stopping a short-half-life serotonergic antidepressant can cause discontinuation syndrome; taper when feasible.
- Serotonin-norepinephrine reuptake inhibitors (SNRIs), bupropion, and mirtazapine are alternatives selected by comorbidity and side-effect profile.
Bipolar Disorder
Bipolar disorder is managed with mood stabilizers (lithium, certain anticonvulsants) and select antipsychotics. Lithium has a narrow therapeutic index and requires serum level monitoring; dehydration, sodium changes, NSAIDs, and certain diuretics or renal decline can raise levels toward toxicity. Antidepressant monotherapy without a mood stabilizer is generally avoided because of the risk of inducing mania.
Schizophrenia
Antipsychotics are the cornerstone of schizophrenia treatment.
| Class | Representative concern | Monitoring emphasis |
|---|---|---|
| First-generation (typical) | Higher extrapyramidal symptoms (EPS) and tardive dyskinesia risk | Movement assessment |
| Second-generation (atypical) | Higher metabolic risk (weight, glucose, lipids) | Weight/BMI, glucose, lipid panel |
| Clozapine (special case) | Risk of severe neutropenia | Required absolute neutrophil count monitoring program |
The exam often asks which monitoring parameter matches a chosen agent — match typical agents to movement disorders and many atypicals to metabolic monitoring.
Neurology
Epilepsy
Antiseizure medication is selected by seizure type, patient factors (pregnancy potential, comorbidities, interactions), and tolerability. High-yield concepts include enzyme-inducing interactions with several older agents, the need for adherence to maintain seizure control, and pregnancy-related counseling (some agents carry higher teratogenic risk and require preconception planning with the care team). Therapeutic drug monitoring is used for selected agents with established target ranges.
Parkinson Disease
Levodopa-carbidopa is the most effective symptomatic therapy for Parkinson disease motor symptoms. Carbidopa inhibits peripheral decarboxylase so less levodopa is converted to dopamine outside the central nervous system, which reduces peripheral nausea and increases central availability. Dopamine agonists and other adjuncts are used by stage and side-effect profile; abrupt withdrawal of dopaminergic therapy can cause serious deterioration.
Pain and Opioids
Pain management follows a patient-specific, often stepwise approach using non-opioid analgesics where appropriate before or alongside opioids. Key NAPLEX safety themes:
- Acetaminophen has a maximum daily dose ceiling and hepatotoxicity risk, especially with combination products and alcohol use.
- NSAIDs carry gastrointestinal, renal, and cardiovascular risks; caution in renal impairment, heart failure, and ulcer history.
- Opioids require counseling on sedation, constipation (offer a bowel regimen proactively), respiratory depression, and the risk of additive central nervous system depression with benzodiazepines and alcohol.
- Naloxone access and counseling are emphasized for patients at elevated overdose risk.
Gastroenterology
| Condition | First-line / key principle |
|---|---|
| GERD (gastroesophageal reflux disease) | Lifestyle measures plus acid suppression; proton pump inhibitors (PPIs) for erosive or moderate-to-severe disease |
| Peptic ulcer disease (PUD) | Stop the offending NSAID if applicable; PPI healing therapy; test for and eradicate Helicobacter pylori when present |
| Inflammatory bowel disease (IBD) | Therapy differs by ulcerative colitis vs Crohn disease, extent, and severity (aminosalicylates, corticosteroids for flares, immunomodulators, biologics) |
| Nausea/vomiting | Choose antiemetic by mechanism/etiology (e.g., serotonin antagonists for chemotherapy-related nausea); watch QT and constipation effects |
Counseling cue: PPIs are most effective taken before a meal; long-term use prompts periodic reassessment of ongoing need. H. pylori-positive ulcers are not durably healed by acid suppression alone — eradication is required.
High-Yield Neuro-Psych Emergencies and Syndromes
The NAPLEX repeatedly contrasts drug-induced syndromes that look similar but demand different management.
| Syndrome | Trigger | Hallmark features | Key action |
|---|---|---|---|
| Serotonin syndrome | Excess serotonergic agents (SSRI + MAOI, tramadol, linezolid, triptans) | Rapid onset, hyperreflexia/clonus, agitation, autonomic instability | Stop serotonergic drugs; supportive care; cyproheptadine if severe |
| Neuroleptic malignant syndrome (NMS) | Antipsychotics (dopamine blockade) | Slow onset, "lead-pipe" rigidity, high fever, elevated CK | Stop the antipsychotic; supportive care; dantrolene/bromocriptine if severe |
| Extrapyramidal symptoms (EPS) | First-generation antipsychotics | Acute dystonia, akathisia, parkinsonism | Anticholinergic (benztropine) for acute dystonia |
| Tardive dyskinesia | Long-term dopamine blockade | Late, often irreversible involuntary movements | Reassess antipsychotic; VMAT2 inhibitor option |
Distinguishing pearl: Serotonin syndrome features clonus and hyperreflexia with fast onset, while NMS features rigidity and bradyreflexia with slower onset. The drug class in the stem usually points to the answer — serotonergic agents versus dopamine-blocking antipsychotics.
Seizure-Type Matching and Headache Therapy
Antiseizure selection follows seizure type. Broad-spectrum agents (levetiracetam, lamotrigine, valproate) cover focal and generalized seizures; some narrow-spectrum sodium-channel agents (carbamazepine, phenytoin) can worsen certain generalized seizures such as absence and myoclonic. Valproate is highly effective but is among the most teratogenic options, so people who can become pregnant require careful counseling and effective contraception; lamotrigine requires slow titration to avoid serious rash (Stevens-Johnson syndrome).
For migraine, distinguish acute (abortive) from preventive therapy. Acute options include NSAIDs, triptans (avoid in uncontrolled hypertension or known coronary disease), and newer gepants/ditans. Preventive therapy (beta-blockers, topiramate, certain antidepressants, CGRP monoclonal antibodies) is added when attacks are frequent or disabling. Counsel against medication-overuse headache from frequent acute therapy, and remember triptans are serotonergic and contribute to serotonin syndrome risk when combined with other serotonergic drugs.
A patient with bipolar disorder maintained on lithium develops vomiting and diarrhea from a viral illness and becomes volume-depleted. She has also started taking an over-the-counter NSAID for body aches. Which is the most important pharmacist concern?
A patient newly diagnosed with major depressive disorder is started on an SSRI and asks how soon to expect benefit. Which counseling statement is most accurate?
A patient with a duodenal ulcer tests positive for Helicobacter pylori. The patient has been taking a proton pump inhibitor with symptomatic relief. Which statement reflects appropriate management?
A patient on an antipsychotic develops high fever, severe 'lead-pipe' muscular rigidity, and a markedly elevated creatine kinase over several days. Which syndrome is most likely, and what is the immediate action?
A patient with frequent migraines and a history of coronary artery disease asks about a triptan for acute attacks. What is the most appropriate counseling point?