How long do substances or remnants of medicines remain in the body?

Answer

Hi Chris,

This question cannot be answered unequivocally, because it depends on many factors.

First and foremost, the type of medicine. Here we can distinguish two large groups. The water soluble and the fat soluble. The most common, water-soluble are excreted relatively quickly, for example phenylephrine hydrochloride from rhinatiol. The chlorphenamine (rhinatiol) and desloratadine (aerius) will also dissolve quite well. In addition, the liver will make these substances extra water-soluble so that they can be quickly removed from the body through the urine. After 24 hours you will no longer find most of the substances in the body. It is different with fat-soluble substances, for example isotretinoin, a vitamin A analogue taken to treat severe acne. These and other fat-soluble substances accumulate in the fat cells. If this is stopped, this substance will gradually disappear again, but this is very slowly. With isotretinoin, for example, women are still not allowed to become pregnant until at least 5 weeks after stopping because this substance can cause miscarriages.

Irrespective of the nature of the drug, there are individual and age-related factors that may affect excretion. Interactions with other medicines and (congenital) diseases can also have an influence.

Studies that determine the dose of the drug take a closer look at the absorption (absorption), distribution, metabolism (change of the substance in the body) and elimination (ADME) of the substance. The safe dose for the general population is determined. Exceptions are stated in the package leaflet and the doctor takes them into account when prescribing.

Hopefully I have given you a little more insight into the wonderful world of the pharmaceutical substances in our body.