Chronotherapy: Why Timing Drugs to Our Body Clocks May Work

Do drugs work better if taken by the clock?

A new analysis published in this month’s issue of The Lancet journal’s eClinicalMedicine suggests: Yes, they do — if you consider the patient’s individual body clock. The study is the first to find that timing blood pressure drugs to a person’s personal “chronotype” — that is, whether they are a night owl or an early bird — may reduce the risk for a heart attack.

The findings represent a significant advance in the field of circadian medicine or “chronotherapy” — timing drug administration to circadian rhythms. A growing stack of research suggests this approach could reduce side effects and improve the effectiveness of a wide range of therapies, including vaccines, cancer treatments, and drugs for depression, glaucoma, pain, seizures, and other conditions. Still, despite decades of research, time of day is rarely considered in writing prescriptions.

“We are really just at the beginning of an exciting new way of looking at patient care,” said Kenneth A. Dyar, PhD, whose lab at Helmholtz Zentrum München’s Institute for Diabetes and Cancer focuses on metabolic physiology. Dyar is co-lead author of the new blood pressure analysis.

“Chronotherapy is a rapidly growing field,” he said, “and I suspect we are soon going to see more and more studies focused on ‘personalized chronotherapy,’ not only in hypertension but also potentially in other clinical areas.”

The ‘Missing Piece’ in Chronotherapy Research

Blood pressure drugs have long been chronotherapy’s battleground. After all, blood pressure follows a circadian rhythm, peaking in the morning and dropping at night.

That healthy overnight dip can disappear in people with diabetes, kidney disease, and obstructive sleep apnea. Some physicians have suggested a bed-time dose to restore that dip. But studies have had mixed results, so “take at bedtime” has become a less common recommendation in recent years.

But the debate continued. After a large 2019 Spanish study found that bedtime doses had benefits so big that the results drew questions, an even larger, 2022 randomized, controlled trial from the University of Dundee in Dundee, Scotland — called the TIME study — aimed to settle the question.

Researchers assigned over 21,000 people to take morning or night hypertension drugs for several years and found no difference in cardiovascular outcomes.

“We did this study thinking nocturnal blood pressure tablets might be better,” said Thomas MacDonald, MD, professor emeritus of clinical pharmacology and pharmacoepidemiology at the University of Dundee and principal investigator for the TIME study and the recent chronotype analysis. “But there was no difference for heart attacks, strokes, or vascular death.”

So, the researchers then looked at participants’ chronotypes, sorting outcomes based on whether the participants were late-to-bed, late-to-rise “night owls” or early-to-bed, early-to-rise “morning larks.”

Their analysis of these 5358 TIME participants found the following results: Risk for hospitalization for a heart attack was at least 34% lower for “owls” who took their drugs at bedtime. By contrast, owls’ heart attack risk was at least 62% higher with morning doses. For “larks,” the opposite was true. Morning doses were associated with an 11% lower heart attack risk and night doses with an 11% higher risk, according to supplemental data.

The personalized approach could explain why some previous chronotherapy studies have failed to show a benefit. Those studies did not individualize drug timing as this one did. But personalization could be key to circadian medicine’s success.

“Our ‘internal personal time’ appears to be an important variable to consider when dosing antihypertensives,” said co-lead author Filippo Pigazzani, MD, PhD, clinical senior lecturer and honorary consultant cardiologist at the University of Dundee School of Medicine. “Chronotherapy research has been going on for decades. We knew there was something important with time of day. But researchers haven’t considered the internal time of individual people. I think that is the missing piece.”

The analysis has several important limitations, the researchers said. A total of 95% of participants were White. And it was an observational study, not a true randomized comparison. “We started it late in the original TIME study,” MacDonald said. “You could argue we were reporting on those who survived long enough to get into the analysis.” More research is needed, they concluded.

Looking Beyond Blood Pressure

What about the rest of the body? “Almost all the cells of our body contain ‘circadian clocks’ that are synchronized by daily environmental cues, including light-dark, activity-rest, and feeding-fasting cycles,” said Dyar.

An estimated 50% of prescription drugs hit targets in the body that have circadian patterns. So, experts suspect that synching a drug with a person’s body clock might increase effectiveness of many drugs.

A handful of US Food and Drug Administration–approved drugs already have time-of-day recommendations on the label for effectiveness or to limit side effects, including bedtime or evening for the insomnia drug Ambien, the HIV antiviral Atripla, and cholesterol-lowering Zocor. Others are intended to be taken with or after your last meal of the day, such as the long-acting insulin Levemir and the cardiovascular drug Xarelto. A morning recommendation comes with the proton pump inhibitor Nexium and the attention-deficit/hyperactivity disorder drug Ritalin.

Interest is expanding. About one third of the papers published about chronotherapy in the past 25 years have come out in the past 5 years. The May 2024 meeting of the Society for Research on Biological Rhythms featured a day-long session aimed at bringing clinicians up to speed. An organization called the International Association of Circadian Health Clinics is trying to bring circadian medicine findings to clinicians and their patients and to support research.

Moreover, while recent research suggests minding the clock could have benefits for a wide range of treatments, ignoring it could cause problems.

In a Massachusetts Institute of Technology study published in April in Science Advances, researchers looked at engineered livers made from human donor cells and found more than 300 genes that operate on a circadian schedule, many with roles in drug metabolism. They also found that circadian patterns affected the toxicity of acetaminophen and atorvastatin. Identifying the time of day to take these drugs could maximize effectiveness and minimize adverse effects, the researchers said.

Timing and the Immune System

Circadian rhythms are also seen in immune processes. In a 2023 study in The Journal of Clinical Investigation of vaccine data from 1.5 million people in Israel, researchers found that children and older adults who got their second dose of the Pfizer mRNA COVID vaccine earlier in the day were about 36% less likely to be hospitalized with SARS-CoV-2 infection than those who got an evening shot.

“The sweet spot in our data was somewhere around late morning to late afternoon,” said lead researcher Jeffrey Haspel, MD, PhD, associate professor of medicine in the Division of Pulmonary and Critical Care Medicine at Washington University School of Medicine in St. Louis.

In a multicenter, 2024 analysis of 13 studies of immunotherapy for advanced cancers in 1663 people, researchers found treatment earlier in the day was associated with longer survival time and longer survival without cancer progression.

“Patients with selected metastatic cancers seemed to largely benefit from early [time of day] infusions, which is consistent with circadian mechanisms in immune-cell functions and trafficking,” the researchers noted. But “retrospective randomized trials are needed to establish recommendations for optimal circadian timing.”

Other research suggests or is investigating possible chronotherapy benefits for depression, glaucoma, respiratory diseases, stroke treatment, epilepsy, and sedatives used in surgery. So why aren’t healthcare providers adding time of day to more prescriptions? “What’s missing is more reliable data,” Dyar said.

Should You Use Chronotherapy Now?

Experts emphasize that more research is needed before doctors use chronotherapy and before medical organizations include it in treatment recommendations. But for some patients, circadian dosing may be worth a try:

Night owls whose blood pressure isn’t well-controlled. Dyar and Pigazzani said night-time blood pressure drugs may be helpful for people with a “late chronotype.” Of course, patients shouldn’t change their medication schedule on their own, they said. And doctors may want to consider other concerns, like more overnight bathroom visits with evening diuretics.

In their study, the researchers determined participants’ chronotype with a few questions from the Munich Chronotype Questionnaire about what time they fell asleep and woke up on workdays and days off and whether they considered themselves “morning types” or “evening types.” (The questions can be found in supplementary data for the study.)

If a physician thinks matching the timing of a dose with chronotype would help, they can consider it, Pigazzani said. “However, I must add that this was an observational study, so I would advise healthcare practitioners to wait for our data to be confirmed in new RCTs of personalized chronotherapy of hypertension.”

Children and older adults getting vaccines. Timing COVID shots and possibly other vaccines from late morning to mid-afternoon could have a small benefit for individuals and a bigger public-health benefit, Haspel said. But the most important thing is getting vaccinated. “If you can only get one in the evening, it’s still worthwhile. Timing may add oomph at a public-health level for more vulnerable groups.”