Blood Pressure and Heart Rate Effects, Weight Loss and Maintenance During Long‐Term Phentermine Pharmacotherapy for Obesity

Abstract

There is a perception that phentermine pharmacotherapy for obesity increases blood pressure and heart rate (HR), exposing treated patients to increased cardiovascular risk. We collected data from phentermine‐treated (PT) and phentermine‐untreated (P0) patients at a private weight management practice, to examine blood pressure, HR, and weight changes. Records of 300 sequential returning patients were selected who had been treated with a low‐carbohydrate ketogenic diet if their records included complete weight, blood pressure, and HR data from seven office examinations during the first 12 weeks of therapy. The mean time in therapy, time range, and mode was 92 (97.0), 12–624, and 52 weeks. 14% were normotensive, 52% were prehypertensive, and 34% were hypertensive at their first visit or had a previous diagnosis of hypertension. PT subjects systolic blood pressure/diastolic blood pressure (SBP/DBP) declined from baseline at all data points (SBP/DBP −6.9/−5.0 mm Hg at 26, and −7.3/−5.4 at 52 weeks). P0 subjects' declines of SBP/DBP at both 26 and 52 weeks were −8.9/−6.3 but the difference from the treated cohort was not significant. HR changes in treated/untreated subjects at weeks 26 (−0.9/−3.5) and 52 (+1.2/−3.6) were not significant. Weight loss was significantly greater in the PT cohort for week 1 through 104 (P = 0.0144). These data suggest phentermine treatment for obesity does not result in increased SBP, DBP, or HR, and that weight loss assisted with phentermine treatment is associated with favorable shifts in categorical blood pressure and retardation of progression to hypertension in obese patients.

Advances in Medical Therapy for Weight Loss and the Weight-Centric Management of Type 2 Diabetes Mellitus

“…Additionally, at 52 weeks, systolic and diastolic blood pressure had decreased from baseline in both groups (phentermine: systolic −7.3 mmHg, diastolic −5.4 mmHg; placebo: systolic −8.9 mmHg, diastolic −6.3 mmHg) but the blood pressure difference between groups was not significant despite greater weight loss in the phentermine group. Heart rate changes in the phentermine and placebo groups were also not significantly different at 26 weeks (phentermine −0.9 beats per minute [bpm]; placebo −3.5 bpm) or 52 weeks (phentermine +1.2 bpm; placebo −3.6 bpm) [50].…”

“…Given the increased release of norepinephrine promoted by phentermine, it has the potential to raise blood pressure and heart rate in some patients [48,49]. A recent study by Hendricks et al [50] examined the impact of treatment with phentermine monotherapy and a lowcarbohydrate diet in 300 obese subjects. Weight loss was significantly greater in the phentermine group as compared to placebo beginning at week 1 and continuing through week 104 (P=0.0144).…”

A review of late-stage CNS drug candidates for the treatment of obesity

“…It has recently been reported that abrupt cessation of phentermine in obese subjects on long-term therapy with this psychostimulant did not evoke withdrawal or drug craving. 65 Fixed-dose drug combinations The move by several biotech companies to develop fixed-dose combinations containing approved CNS drugs to treat obesity has a number of drivers. First, it is evident that weight loss can be achieved using currently available antiobesity drugs and they deliver medical benefits to the patient in terms of improved glycaemic control, reduced plasma concentrations of dangerous lipids and reductions in blood pressure.…”

New options for the treatment of obesity and type 2 diabetes mellitus (narrative review)

“…Four medications, benzphetamine, diethylpropion, phendimetrazine, and phentermine, are approved for the short-term treatment of obesity (Bray & Ryan, 2012). Although longer term weight loss data on phentermine and related changes in BP and heart rate have been published, it is not approved in the United States for use beyond a few weeks and is not approved in Europe (Hendricks, Greenway, Westman, & Gupta, 2011). In addition, pharmacotherapies for chronic weight management in adults are now available, including orlistat and 2 pharmaceuticals recently approved by the US FDA, lorcaserin and PHEN/TPM ER.…”