Ritchey ME, Harding A, Hunter S, Peterson C, Sager PT, Kowey PR, Nguyen L, Thomas S, Cainzos-Achirica M, Rothman KJ, Andrews EB, Anthony MS. Cardiovascular safety during and after use of phentermine and topiramate. J Clin Endocrinol Metab. 2019 Feb 1;104(2):513-22. doi: 10.1210/jc.2018-01010

CONTEXT: Increases in heart rate were seen during the clinical program for fixed-dose combination phentermine (PHEN) and topiramate (TPM), an oral medication indicated for weight management; however, the effect on cardiovascular (CV) outcomes is uncertain.

OBJECTIVE: The aim of the present study was to determine the extent to which the rates of major adverse CV events (MACE) in patients using PHEN and TPM (including fixed dose) differed from the MACE rates during unexposed periods. DESIGN: Retrospective cohort study.

SETTING: MarketScan, US insurance billing data.

PATIENTS OR OTHER PARTICIPANTS: Patients aged >18 years with ≥6 months of continuous enrollment in the database before taking PHEN and/or TPM or after stopping these medications.

INTERVENTIONS: PHEN and TPM, taken separately and together (including fixed dose).

MAIN OUTCOME MEASURES: MACE, a composite of hospitalization for acute myocardial infarction and stroke and in-hospital CV death.

RESULTS: Because the outcomes are rare and the duration of medication use was brief, few events occurred. The MACE rates among current users of PHEN/TPM, fixed-dose PHEN/TPM, and PHEN were lower than those among unexposed former users. In contrast, the rate of MACE among current users of TPM was greater than among unexposed former users [incidence rate ratio: PHEN/TPM, 0.57; 95% CI, 0.19 to 1.78; fixed-PHEN/TPM, 0.24; 95% CI, 0.03 to 1.70; PHEN, 0.56; 95% CI, 0.34 to 0.91; TPM, 1.58; 95% CI, 1.33 to 1.87).

CONCLUSIONS: Overall, the data indicated no increased risk of MACE for current PHEN/TPM users; however, the 95% CIs for the PHEN/TPM groups were broad, indicating that the data were compatible with a wide range of possible values.

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