What lab tests, including liver function tests (LFTs) and complete blood count (CBC), should be monitored before prescribing a selective serotonin reuptake inhibitor (SSRI) to a patient, especially those with a history of liver disease or bleeding disorders?

Laboratory Monitoring Before Prescribing SSRIs

Before prescribing an SSRI, no routine laboratory tests are strictly required in healthy patients, but baseline complete blood count (CBC) and liver function tests (LFTs) should be obtained in patients with a history of liver disease or bleeding disorders.

Essential Baseline Testing

For Patients with Liver Disease History

• Obtain comprehensive liver function tests including AST, ALT, alkaline phosphatase, total bilirubin, and albumin before initiating SSRI therapy 1, 2
• Liver function tests provide critical baseline values to monitor for potential hepatotoxicity, particularly since SSRIs can affect hepatic function in patients with pre-existing liver compromise 1
• The prothrombin time and serum albumin level are excellent gauges of hepatic protein synthetic ability and should be included in the baseline assessment 1

For Patients with Bleeding Disorder History or Risk Factors

• Obtain a complete blood count with platelet count to establish baseline hematologic parameters 3
• SSRIs approximately double the odds of upper gastrointestinal bleeding by blocking serotonin uptake into platelets, impairing the platelet hemostatic response 3
• The absolute risk of bleeding with SSRIs is low, but precautions are necessary in high-risk patients such as those with acid-peptic disease, history of bleeds, or cirrhosis 3

Risk-Stratified Approach

High-Risk Patients Requiring Baseline Labs

Patients with liver disease:

• Those with cirrhosis or liver failure have significantly increased risk of SSRI-associated bleeding 3
• Baseline LFTs (AST, ALT, alkaline phosphatase, bilirubin, albumin) are essential 1, 2
• Consider prothrombin time to assess hepatic synthetic function 1

Patients with bleeding risk factors:

• History of gastrointestinal bleeding or peptic ulcer disease 3
• Concurrent use of NSAIDs, anticoagulants, or antiplatelet agents (which increases bleeding risk) 3
• Baseline CBC with platelet count is warranted 3

Patients with multiple comorbidities:

• Consider baseline renal function (BUN, creatinine) if there are concerns about drug clearance 2
• Electrolytes may be relevant in elderly patients at risk for SSRI-induced hyponatremia 2

Standard-Risk Patients

• No routine laboratory testing is required before initiating SSRI therapy in otherwise healthy patients without liver disease, bleeding history, or concurrent high-risk medications 3
• Clinical assessment and medication history review are sufficient for most patients 3

Common Pitfalls to Avoid

• Do not routinely order extensive laboratory panels in healthy patients without risk factors, as this is not cost-effective and lacks evidence-based support 2
• Do not assume normal baseline labs eliminate bleeding risk when SSRIs are combined with NSAIDs or anticoagulants; the risk is synergistic 3
• Do not overlook liver disease history, as patients with cirrhosis or liver failure have substantially increased bleeding risk with SSRIs 3
• Consider adding proton pump inhibitor prophylaxis in high-risk patients rather than avoiding SSRIs, as PPIs decrease SSRI-associated GI bleeding risk 3

Ongoing Monitoring Considerations

• Routine laboratory monitoring during SSRI therapy is generally not required unless baseline abnormalities were present or symptoms develop 3
• If symptoms of hepatotoxicity (jaundice, malaise, unexplained deterioration) or bleeding occur, obtain immediate laboratory evaluation 3, 1
• In patients with pre-existing liver disease, periodic monitoring of LFTs may be prudent, though specific intervals are not established for SSRIs 1, 2