Can I prescribe phentermine (anorexiant) to a patient with a heart murmur?

From the Guidelines

Prescribing phentermine to a patient with a heart murmur is not recommended due to the potential risk of worsening cardiovascular conditions. Phentermine is a sympathomimetic amine that stimulates the central nervous system and increases blood pressure and heart rate, which could potentially exacerbate underlying cardiac abnormalities indicated by the heart murmur 1. According to the AGA clinical practice guideline on pharmacological interventions for adults with obesity, phentermine should be avoided in patients with a history of cardiovascular disease 1.

The guideline suggests that phentermine monotherapy is approved by the FDA for short-term use (12 weeks), but many practitioners use it longer than 12 weeks in an off-label fashion 1. However, the guideline also states that phentermine should be avoided in patients with a history of cardiovascular disease, and blood pressure and heart rate should be monitored periodically while taking phentermine 1.

A more recent study published in 2022 also advises caution when using phentermine, particularly in patients with a history of cardiovascular disease or uncontrolled hypertension 1. The study notes that phentermine can increase cardiac workload and potentially exacerbate underlying cardiac conditions, and therefore should be avoided in patients with significant cardiac conditions 1.

In light of this evidence, it is recommended to consult with a cardiologist before prescribing phentermine to patients with any cardiac findings, including heart murmurs. Alternative weight management approaches such as lifestyle modifications, dietary changes, and non-stimulant medications would be safer options for these patients 1.

Some key considerations when evaluating the use of phentermine in patients with heart murmurs include:

• The nature and severity of the murmur
• The presence of underlying cardiac abnormalities
• The potential risk of worsening cardiovascular conditions
• The need for careful monitoring of blood pressure and heart rate
• The consideration of alternative weight management approaches.

Overall, the potential risks associated with phentermine use in patients with heart murmurs outweigh the potential benefits, and alternative approaches should be considered 1.

From the FDA Drug Label

5.3 Valvular Heart Disease Serious regurgitant cardiac valvular disease, primarily affecting the mitral, aortic and/or tricuspid valves, has been reported in otherwise healthy persons who had taken a combination of phentermine with fenfluramine or dexfenfluramine for weight loss The possible role of phentermine in the etiology of these valvulopathies has not been established and their course in individuals after the drugs are stopped is not known. The possibility of an association between valvular heart disease and the use of phentermine alone cannot be ruled out; there have been rare cases of valvular heart disease in patients who reportedly have taken phentermine alone.

The patient has a heart murmur, which may indicate valvular heart disease. Given the potential association between phentermine and valvular heart disease, as well as the lack of established safety, it is recommended to exercise caution when prescribing phentermine to this patient.

• The decision to prescribe phentermine should be made on a case-by-case basis, considering the potential benefits and risks.
• Close monitoring of the patient's condition is necessary, and the patient should be advised to report any new or worsening symptoms.
• It is also important to consider alternative treatment options for weight loss that may be safer for the patient 2.

From the Research

Phentermine Prescription with Heart Murmur

• The decision to prescribe phentermine to a patient with a heart murmur should be made with caution, considering the potential risks and benefits.
• A study from 3 found that the clinical examination by an experienced pediatric cardiologist is an accurate means of assessing newly referred patients with murmurs, with a sensitivity of 96% and specificity of 95%.
• However, this study does not directly address the safety of prescribing phentermine to patients with heart murmurs.
• Another study from 4 reported a case of supraventricular tachycardia associated with phentermine use, suggesting that the sympathomimetic effects of phentermine may contribute to cardiac arrhythmias.
• A review of phentermine's role in obesity pharmacotherapy from 5 noted that recent research on phentermine is sparse and consists primarily of observational studies with methodologic limitations.
• A study from 6 found no increased risk of major adverse cardiovascular events (MACE) among current users of phentermine, but the confidence intervals were broad, indicating that the data were compatible with a wide range of possible values.
• Another study from 7 reported two cases of women presenting with chest pain and severe coronary vasospasm after initiating phentermine, suggesting that phentermine may have vasospastic properties.
• Considering these findings, it is essential to carefully evaluate the patient's cardiac condition and weigh the potential benefits and risks of phentermine prescription, as supported by studies from 4, 6, and 7.