Why coffee, tea, and water decrease the effectiveness of drugs.

[Jules7890]

I have an essay question asking me why consumption of lots of coffee, tea, or water while a patient is taking a drug could cause the drug to lose its effectiveness more quickly.

Does anyone know? I know it has to do with drugs being excreted in the urine, but I don't understand why increasing the volume of urine would make the drug go through someone's system more quickly. Do the kidneys flush out someone's bloodstream more quickly when there is a higher volume of urine? I'm confused, and I'm not sure if I'm wording my questionn very well.

[iNow]

My first thought was that coffee and tea have caffeine, so speed metabolism. This would mean that the drug is metabolized more quickly, and wouldn't get into the cells as much. Coffee is also a diuretic, so it will pull water FROM the cells to be extreted, and would likely take some of the medicine with it. Also, water would dilute the medicine, and saturate the cells, so the medicine couldn't get in as well.

 

Plus, all of them make you urinate more often and more quickly, so the drug would be extreted before it has a chance to act.

 

Let me be clear. These are all speculations on my part, and I'm not trained formerly in biology or medicine. I just wanted to share my initial thoughts in the hopes that it would stimulate some new thoughts in you. Good luck.

[Mr Skeptic]

Yes, I'd say it is because caffeine is a diuretic. Giving the kidneys more fluid means that they don't have to conserve as much water so they don't need to fight as much osmosis and can concentrate (ha, ha) on excreting toxins (and medicines). More urine also means more chance to remove the toxins (and medicines). I'm also guessing a bit. If this is accurate, then drinking lots of water would have a similar effect.

[sandymb]

I hate to dispel a long standing belief (actually, that's a lie - I actually enjoy dispelling old beliefs), but caffeine has no more of a diuretic effect than plain old water. All fluids, consumed in quantity, are going to have a naturally mild diuretic effect just as a result of increased fluid volume. Too much fluid can have a diluting effect on anything consumed as well as creating electrolyte imbalances which could effect kidney function etc. Just my layman's opinion. Take it for what it's worth.

[John Cuthber]

I think this "caffeine has no more of a diuretic effect than plain old water." constitutes an extraordinary claim. Do you have extraordinary evidence for it?

There is, it seems, a clinical trial that comes to the oposite conclusion.

http://www.aquaban.co.uk/index.asp?Page=aquaban

[Lisa]

Caffeine acts as a psychoactive stimulant (CNS); it crosses the blood brain barrier where it acts as an antagonist inhibitor of adenosine. Caffeine increases epinephrine. Body size, amount of caffeine, and tolerance will vary its effect. Tea, pop and chocolate are also sources of caffeine. Considering the variability between the amount of caffeine that can be digested, the person’s body type, tolerance level and the additional drug(s) would all have to be considered before arriving at a conclusion that there is a decrease in effectiveness when pairing one drug with another. Water in excess can lead to the dilution of sodium in the body. However, I am not aware of a normal amount of water consumption interfering with the mechanism or therapeutic level of a drug(s). Specifically, what drugs are decreased in effectiveness when interacting with caffeine, tea and/or water?