Drugs may be more effective at certain times of day

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Scientists believe that drugs may be more effective if it is taken at a specific time of day. This comes after the discovery that the effectiveness of drugs is linked to the body clock.

It has not been clear why certain drugs, such as aspirin and statins, are more effective if taken in the morning or evening. Scientists wanted to find out if this applied to all medications.

This prompted scientists based at Pennsylvania University to calculate a suitable time of day when genes in body organs are particularly active.

They found that the kidneys and liver are most active after 6pm. The lungs reach their peak at lunchtime, and the heart is more active in the morning. Scientists state that drugs targeting those particular genes will have a different effect depending on the time of day it is taken.

Tests done on mice indicated that almost half of the World Health Organisation’s 250 best-selling medicines have a different effect during the day and night.

Many medications do not remain in the body for long periods, which makes it important to use at a time when it will have the most impact. Taking medication at a time of day when the genes are inactive may render it useless. In contrast, drugs which had been tested in the morning could become toxic if taken in the evening, or vice versa.

According to Professor John Hogenesch proper animal and clinical studies are required, but scientists are now aware of where to look in the body for the best effect.

He said low dose aspirin therapy appears to be more effective if taken prior to bedtime for lowering blood pressure, however at least 50% of patients take aspirin first thing in the morning. He added that there are hundreds of available papers which indicate improved tolerance and effectiveness for chemotherapy, but few cancer patients are offered their medication at a particular time of day.

Doctors have become more interested in chronotherapy, where our medical treatments are aligned to our circadian rhythms, however, this is the first report to be produced indicating the 24-hour patterns of genes in mammals.

This map could aid doctors in calculating how their patients could get the best effect from taking medications at certain times of day.

Almost all living organisms have an internal clock which tunes bodily functions into the 24-hour day-night period. This clock is regulated by bodily senses in humans and other mammals, particularly the way in which the eyes perceive dark and light and the change in skin temperature. This mechanism controls our sleep and waking patterns.

The study found that 43% of all protein-coding genes have circadian rhythms. The liver appeared to be the most rhythmic of all the organs, and has high genetic activity before dawn and before dusk.

This type of study has been ongoing for almost forty years and successes which have come from it include short-acting statins, low-dose aspirin and chemotherapeutics. However, most of this was initiated by trial and error.

Professor Hogenesch said that they are now aware that drugs are under clock control and when and where they cycle within the body. He said this offers an opportunity for potential chronotherapy.

He added that the next step forward would be to apply this knowledge to particular animal models to determine the time of effectiveness. It will require in-depth clinical studies to determine the optimal time for drug-taking.

Image Credit: Brandon Giesbrecht

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