University of Dundee and College of London researchers have found that a person taking the maximum, daily dose of some medicines would exceed the recommended daily dietary intake limits for sodium. In Australia, the total maximum recommended limit of sodium for adults should be less than 2300 mg per day (less for children). The label on the Alka-Seltzer tablets carries a warning that you should not take more than 8 tablets per day.
In the study, the researchers found that patients taking the sodium-containing medication had a 16% increased risk of a heart attack, were 7 times more likely to develop high blood pressure, and, were 28% more likely to die, compared with patients who took the non-sodium containing versions of the same drug.
So why do we add sodium to drugs if it is potentially harmful?
We do this because many drugs are actually insoluble in water. The cells in your body are made up mostly of water, so if you want to be able to transport a drug around the body, and have it absorbed into cells, it is beneficial if the drug is soluble in water.
How do we add sodium to drugs?
If the drug is, for example, a weak acid like aspirin, then it is not very soluble in water.
Being a weak acid, though, aspirin can undergo a proton transfer (neutralisation) reaction with a base such as sodium hydroxide. The product of a neutralisation reaction are salt and water.
acid + base → salt + water
aspirin + sodium hydroxide → sodium salt of aspirin + water
The sodium salt of aspirin readily dissolves in water by dissociating into positive sodium ions and negative "aspirin" ions.
BMJ-British Medical Journal (2013, November 26). High salt levels in medicines increase risk of cardiovascular events. ScienceDaily. Retrieved November 28, 2013, from http://www.sciencedaily.com /releases/2013/11/131126191557.htm
proton transfer reactions
acid dissociation constants
Suggested Study Questions:
- Convert these masses in milligrams to masses in grams
- 324 mg
- 445 mg