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Difficulty: MediumMonitoring and Treatment Evaluation

During an outpatient rheumatology consultation, a 47-year-old female patient is diagnosed with seropositive rheumatoid arthritis following a four-month history of bilateral symmetric swelling in her proximal interphalangeal and metacarpophalangeal joints. The physician and patient engage in shared decision-making and agree to initiate systemic disease-modifying antirheumatic drug (DMARD) therapy with weekly oral methotrexate. The patient has a history of mild essential hypertension and takes amlodipine. Which of the following baseline evaluations are necessary to safely initiate and subsequently monitor this specific pharmacotherapy? (Select the three that apply)

  1. Complete blood countAnswer
  2. Serum aminotransferasesAnswer
  3. Serum creatinineAnswer
  4. D
    Thiopurine methyltransferase activity testing
  5. E
    High-resolution computed tomography of the chest

Answer

The correct baseline and ongoing evaluations for methotrexate therapy are a complete blood count, serum aminotransferases, and serum creatinine.
Methotrexate is a folate antimetabolite and the preferred initial disease-modifying antirheumatic drug (DMARD) for rheumatoid arthritis. Because of its toxicity profile, stringent baseline and ongoing laboratory monitoring are required. Methotrexate is primarily excreted by the kidneys; therefore, a baseline serum creatinine is essential to identify renal impairment, which increases the risk of severe toxicity and may require dose adjustment or represent a contraindication. Additionally, methotrexate carries risks of hepatotoxicity and dose-dependent bone marrow suppression. Consequently, baseline and periodic monitoring of serum aminotransferases (to detect liver injury) and a complete blood count (to monitor for myelosuppression, including leukopenia, anemia, and thrombocytopenia) are mandatory.

Step-by-Step Solution

1
Identify the initiated medication and its indication
The patient is starting methotrexate for moderate-to-severe rheumatoid arthritis.
Different DMARDs have unique toxicity profiles that dictate necessary baseline testing.
2
Recall the major toxicities and excretion pathways of the medication
Methotrexate can cause myelosuppression and hepatotoxicity, and it is renally excreted.
Monitoring parameters are directly linked to preventing or detecting these specific adverse effects.
3
Select the laboratory tests that monitor these specific systems
Complete blood count, serum aminotransferases, and serum creatinine are identified as the necessary tests.
These tests ensure the drug can be safely cleared and check for its primary organ toxicities.

Key Concept

Methotrexate requires baseline and ongoing monitoring of renal function (serum creatinine), hepatic function (serum aminotransferases), and bone marrow function (complete blood count) due to its clearance mechanism and toxicity profile.
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Topics

Monitoring and Treatment Evaluation

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