Pharmacology · patient case question
Before proceeding with surgical treatment, which laboratory assessment is most important given her medication list?
Patient case: Rheumatoid Arthritis and a Needed Extraction
Patient: 56-year-old female
Chief Complaint: “My back bottom left tooth has been aching for two weeks.”
Background: Rheumatoid arthritis for 12 years, currently in partial remission. Reports hives after amoxicillin as a teenager. No other systemic disease.
Medications: Methotrexate 15 mg weekly · Adalimumab (Humira) 40 mg subcutaneous every 2 weeks · Folic acid 1 mg daily
Vital Signs: BP 124/76 mmHg · HR 78 bpm · RR 16 · T 98.6°F
Findings: Maximum interincisal opening 32 mm with bilateral TMJ crepitus. Ulnar deviation of the fingers with metacarpophalangeal swelling. Tooth #18 with a grossly carious crown, non-restorable; extraction planned.
Show answer and explanation
Correct answer: C. Creatinine clearance
- A. Incorrect. A lipid panel is relevant to cardiovascular risk management, not to methotrexate or adalimumab safety.
- B. Incorrect. Prothrombin time evaluates the extrinsic pathway and is used to monitor warfarin or assess hepatic synthetic function. Neither of her medications affects it.
- C. Correct. Methotrexate is cleared almost entirely by the kidney, so declining renal function causes drug accumulation and severe myelosuppression. Renal function assessment, alongside a complete blood count and liver enzymes, is the appropriate baseline before surgery and before prescribing any drug with renal clearance.
- D. Incorrect. Serum amylase is used to investigate pancreatitis or salivary gland disease and has no bearing on her therapy.
Note: Avoid or use caution with NSAIDs in a patient on methotrexate. NSAIDs reduce renal clearance of methotrexate and can precipitate toxicity, which makes acetaminophen the safer analgesic choice here.