How to discuss medication efficacy among patients with obesity
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Healio spoke with Grace Cheng, PharmD, APh, BCACP, BCGP, about what types of medication may have lowered efficacy among patients with obesity, how to inform patients about these medications and more.
Cheng is a clinical pharmacist for the UCMyRx Program in the department of medicine at the University of California, Los Angeles.
Healio: What common medications are less effective among patients with obesity compared with those who are not?
Cheng: Common medication classes that may be less effective in patients with obesity are antibiotics and anticoagulants. There also has been limited but inconsistent evidence as to whether or not contraceptive medications may be less effective in women with obesity.
Healio: Why are these drugs less effective among patients with obesity?
Cheng: Several factors may determine the drug concentrations within patients to achieve therapeutic outcomes and minimize adverse events, such as dose, formulation, chemical structure, volume of distribution, comorbidities, renal and/or hepatic function, etc. The therapeutic window for antibiotics and anticoagulants is generally narrower than those of other medications, where subtherapeutic levels may lead to treatment failure, such antibiotic resistance with antibiotics or thromboembolic events with anticoagulants. Most medications have recommendations and dose adjustments based on renal function. However, in order to determine patient’s renal function (creatinine clearance [CrCl]) via Cockcroft-Gault equation, there is also a lack of standardization on which weight to use between total body weight, ideal body weight and adjusted body weight, thereby making it difficult to appropriately dose adjust.
Healio: How do you discuss drug efficacy with patients who have obesity?
Cheng: Clinicians should discuss with patients potential signs and symptoms of adverse events as well as nonpharmacological management if appropriate, such as secondary forms of contraception. For medications where the therapeutic levels are known and can be obtained, it would be important to discuss the need for routine labs and monitoring tests despite the inconvenience in order to evaluate safety and effectiveness of medications.
Healio: What should clinicians consider when prescribing these medications to patients with obesity?
Cheng: Patients with obesity may need an extended course of treatment; therefore, clinicians should consider closer monitoring (ie, imaging, lab test, etc.) on these patients upon completion of the usual treatment course.
Healio: Are there alternatives to these drugs that are effective among patients with obesity?
Cheng: For antibiotics and anticoagulants, there are alternatives that may be effective among patients with obesity; however, several factors including site of infection/thromboembolic events, resistance patterns and formulations may contribute to the clinical decision as to which agents are optimal for a specific patient. As for contraceptives, there are alternative forms of contraception that may be effective regardless of patients’ weight, such as condom, intrauterine devices, etc.
Healio: What additional research is needed to assess drug efficacy among patients with obesity?
Cheng: As there are specific guidelines to evaluate drug efficacy and safety based on hepatic and renal function, there should also be additional guidelines and more clinical research to determine drug efficacy and safety in patients with obesity.
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