What should be assessed before initiating therapy with xanthines?

Assessing baseline labs, particularly liver function tests, is crucial before initiating therapy with xanthines because these medications, such as theophylline, are metabolized by the liver. If a patient has impaired liver function, the metabolism of xanthines can be significantly affected, potentially leading to elevated drug levels in the system, which can cause toxicity. Monitoring liver function tests ensures that the patient can safely metabolize the medication and helps guide appropriate dosing.

While the other options are important to consider in the overall management of a patient, they do not directly address the pharmacokinetics and safety profile related to xanthine therapy in the same way that liver function tests do. A patient's smoking history may influence the dosing of xanthines, as smokers generally require higher doses. Previous medication efficacy can help in understanding a patient’s response to treatment, and vital signs are essential for overall patient assessment, but they do not specifically preclude or indicate the need for monitoring liver function when starting xanthine therapy. Thus, baseline liver function tests are fundamentally significant in this context.