Guidelines for the design and conduct of human clinical trials on ingestion-time differences–chronopharmacology and chronotherapy–of hypertension medications

Ramón C. Hermida, Michael H. Smolensky, Horia Balan, Richard J. Castriotta, Juan J. Crespo, Yaron Dagan, Sherine El-Toukhy, José R. Fernández, Garret A. FitzGerald, Akio Fujimura, Yong Jian Geng, Ramón G. Hermida-Ayala, Antonio P. Machado, Luiz Menna-Barreto, Artemio Mojón, Alfonso Otero, R. Daniel Rudic, Eva Schernhammer, Carsten Skarke, Tomoko Y. SteenMartin E. Young, Xiaoyun Zhao

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Current hypertension guidelines fail to provide a recommendation on when-to-treat, thus disregarding relevant circadian rhythms that regulate blood pressure (BP) level and 24 h patterning and medication pharmacokinetics and pharmacodynamics. The ideal purpose of ingestion-time (chronopharmacology, i.e. biological rhythm-dependent effects on the kinetics and dynamics of medications, and chronotherapy, i.e. the timing of pharmaceutical and other treatments to optimize efficacy and safety) trials should be to explore the potential impact of endogenous circadian rhythms on the effects of medications. Such investigations and outcome trials mandate adherence to the basic standards of human chronobiology research. In-depth review of the more than 150 human hypertension pharmacology and therapeutic trials published since 1974 that address the differential impact of upon-waking/morning versus at-bedtime/evening schedule of treatment reveals diverse protocols of sometimes suboptimal or defective design and conduct. Many have been “time-of-day,” i.e. morning versus evening, rather than circadian-time-based, and some relied on wake-time office BP rather than around-the-clock ambulatory BP measurements (ABPM). Additionally, most past studies have been of too small sample size and thus statistically underpowered. As of yet, there has been no consensual agreement on the proper design, methods and conduct of such trials. This Position Statement recommends ingestion-time hypertension trials to follow minimum guidelines: (i) Recruitment of participants should be restricted to hypertensive individuals diagnosed according to ABPM diagnostic thresholds and of a comparable activity/sleep routine. (ii) Tested treatment-times should be selected according to internal biological time, expressed by the awakening and bed times of the sleep/wake cycle. (iii) ABPM should be the primary or sole method of BP assessment. (iv) The minimum-required features for analysis of the ABPM-determined 24 h BP pattern ought to be the asleep (not “nighttime”) BP mean and sleep-time relative BP decline, calculated in reference to the activity/rest cycle per individual. (v) ABPM-obtained BP means should be derived by the so-called adjusted calculation procedure, not by inaccurate arithmetic averages. (vi) ABPM should be performed with validated and calibrated devices at least hourly throughout two or more consecutive 24 h periods (48 h in total) to achieve the highest reproducibility of mean wake-time, sleep-time and 48 h BP values plus the reliable classification of dipping status. (vii) Calculation of minimum required sample size in adherence with proper statistical methods must be provided. (viii) Hypertension chronopharmacology and chronotherapy trials should preferably be randomized double-blind, randomized open-label with blinded-endpoint, or crossover in design, the latter with sufficient washout period between tested treatment-time regimens.

Original languageEnglish (US)
Pages (from-to)1-26
Number of pages26
JournalChronobiology International
Issue number1
StatePublished - 2021


  • Ambulatory blood pressure monitoring
  • blood pressure dipping
  • hypertension chronotherapy
  • hypertension medications
  • sleep-time blood pressure
  • trial design recommendations and guidelines

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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