From the Research
For patients starting Pristiq (desvenlafaxine), baseline laboratory tests should include a comprehensive metabolic panel (CMP), complete blood count (CBC), and thyroid function tests (TSH, free T4). The CMP evaluates liver and kidney function, which is important as desvenlafaxine is primarily eliminated by the kidneys, and dose adjustments are needed for patients with severe renal impairment 1. The CBC helps establish baseline blood cell counts, as SNRIs like Pristiq can rarely cause hematologic abnormalities. Thyroid function tests are important because thyroid disorders can mimic or exacerbate depression symptoms. For patients with cardiovascular risk factors, an ECG may be warranted as SNRIs can affect heart rate and blood pressure. Sodium levels should be monitored, especially in elderly patients or those on diuretics, as SNRIs can occasionally cause hyponatremia, as seen in a case report where a 28-year-old woman developed hyponatraemia after starting treatment with venlafaxine, the parent compound of desvenlafaxine 2. No routine drug level monitoring is required for Pristiq, although therapeutic drug monitoring may be considered in certain cases, such as patients with pharmacodynamic resistance or those at risk of adverse effects 3. Follow-up laboratory testing should be considered based on the patient's clinical response, side effects, and underlying medical conditions.
Some key points to consider when ordering labs for patients starting Pristiq include:
- Monitoring for potential drug-drug interactions, as desvenlafaxine has a relatively low risk of interactions due to its minimal inhibition of CYP enzymes 4
- Assessing the patient's renal function, as desvenlafaxine is primarily eliminated by the kidneys and dose adjustments may be needed in patients with severe renal impairment 1
- Evaluating the patient's cardiovascular risk factors, as SNRIs can affect heart rate and blood pressure 5