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The weight loss drug tirzepatide (Eli Lilly) reduced blood pressure (BP) in a study of adults with obesity, but much of that was likely a result of the weight loss. 

The findings, now published in Hypertension, were originally presented at the American Heart Association meeting in November 2022 and reported by Medscape Medical News at the time.

Tirzepatide, a dual agonist of both the glucagon-like protein-1 (GLP-1) receptor and of glucose-dependent insulinotropic polypeptide (GIP) was approved in May 2022 by the US Food and Drug Administration for the treatment of type 2 diabetes under the name Mounjaro and in November 2023 for the treatment of obesity under the name Zepbound.

The new BP data come from a substudy of the pivotal SURMOUNT-1 trial, which showed "unprecedented" average weight loss amounts of greater than 20% in the majority of the 630 participants with obesity or overweight plus complications (but not diabetes) who were randomized to the 15 mg tirzepatide dose for 72 weeks. 

In the substudy involving 600 SURMOUNT-1 participants, including 145 randomized to tirzepatide, significant 24-hour systolic BP reductions from baseline to 36 weeks of 7.4, 10.6, and 8.0 mmHg occurred with tirzepatide doses of 5 mg, 10 mg, and 15 mg, respectively. All reductions were statistically significant. Significant reductions also occurred in diastolic BP with the 5 mg and 10 mg tirzepatide doses. 

All of the substudy subjects had baseline BP below 130/90 mmHg, but 30% had hypertension and 29% were using at least one antihypertensive medication. The BP reduction with tirzepatide didn't differ between those who were taking antihypertensive medications and those who weren't.

But tirzepatide probably won't be used as an antihypertensive per se, study lead author James A. de Lemos, MD, chief of cardiology at the University of Texas Southwestern University, Dallas, Texas, told Medscape Medical News.  

"Given how much more expensive tirzepatide is than traditional BP medications, I wouldn't look at it as a substitute. A better way to think about it is as a 'bonus effect' of this class of drugs, which might help with long-term BP control and reduce need for other meds and may contribute to long term cardiovascular benefits of the drug."

Changes in 24-hour BP were strongly correlated with body weight reduction, and further analysis indicated that about 70% of the ambulatory BP reduction were mediated by the drop in weight.

"This is a very high mediation amount, meaning that the large majority of the effect on BP is likely from weight reduction, which is consistent with what has been seen with bariatric surgery, for example. Whether there are other nonweight related factors can't really be assessed with our study design," de Lemos said. 

The BP reductions were seen both during the day and at night and were consistent across participants' age, sex, BMI, and hypertension-related factors.

Heart rate also increased, as has been seen with other GLP-1 receptor agonists. At 36 weeks, heart rate increased with tirzepatide vs placebo by 2.1, 2.3, and 5.4 beats per minute with doses of 5 mg, 10 mg, and 15 mg, respectively. The increase was only significant for the 15 mg dose.

The study and this work were supported by Eli Lilly and Company. de Lemos reports participation on a data safety monitoring board or advisory board for Eli Lilly and Company, Novo Nordisk, AstraZeneca, and Amgen and travel support from Eli Lilly and Company. 

Miriam E. Tucker is a freelance journalist based in the Washington DC area. She is a regular contributor to Medscape, with other work appearing in the Washington Post, NPR's Shots blog, and Diatribe. She is on X (formerly Twitter) @MiriamETucker.