For this months drug of the month, I'd like to switch it up. Enjoy
Pharmaceutical Drug Salts
You might have been prescribed a prescription drug in your life. You might have even noticed it had a second word next to that drug name. Hyclate or propionate or some other chemical sounding name might ring a bell. This second word makes the drug a salt in the pharmacy world. What exactly does a salt have to do with pharmaceutical drugs?
Pass the Salts
The first thing that might come to your head when you hear “salt” is that bottle next to the pepper. You would be correct in your thinking. Table salt is a chemical salt with the formula:
NaCl ; Na being sodium and Cl being chloride. Not sure what pepper is!
Why do pharmaceutical companies create pharmaceutical salts?
Location, Location, Location
A pharmaceutical salt is the combination of a drug with another chemical entity to form an electrically neutral complex.1 An electrically neutral complex is when you have an acidic or basic drug and combine it with a chemical of an opposite charge.1 You have a new form of the drug called a salt. This new drug salt now changes the drugs solubility, absorption, transportation, and excretion in the body.2 Changes in these properties allow a drug it do act in different areas of the body. This is a common practice as many common prescription drugs exist as salts.3 Some salts that you may have heard of include sodium, succinate, and citrate to name a few.4
The Salts in Doxycycline
I’d like you give you an example of a drug with various salts. Doxycycline is a drug used for the treatment in a wide variety of infections caused by bacteria.5 However, it can come in various forms and I don’t mean tablets, capsules, solutions, etc. I’m talking about the salt forms. This drug comes in various salts including hyclate, monohydrate, hydrochloride and calcium.6 When comparing the hyclate vs monohydrate forms of doxycycline, the hyclate is more water soluble than the monohydrate form.7 Conversely, drugs that have lower water solubility have slower drug absorption. They stay in your stomach longer, leading to higher rates of stomach issues.8 This difference in water solubility is important in manufacturing. However, once absorbed they become the same active form.7 A manufacturer may come up with various salt forms of a drug depending on how they want it to act.
Drugs names can be confusing to pronounce and come in various forms. This confusion can be exacerbated with the addition of another word next to the drug. Now you know the purpose of that other word, the pharmaceutical salt. Whether you are in the pharmacy practice or a patient, this knowledge can provide an extra sense of awareness regarding your medication.
Patel A, Jones S, Ferro A, Patel N. Pharmaceutical salts: a formulation trick or a clinical conundrum? The British Journal of Cardiology. Br J Cardiol 2009;16:281-6.
Sandmann BJ, Dash AK, Al-Achi A, Greenwood R. Applied Physical Pharmacy. 3rd e. McGraw-Hill Education; 2019. https://accesspharmacy-mhmedical-com.mwu.idm.oclc.org/content.aspx?sectionid=218642500&bookid=2619#1163540067. Accessed April 24th, 2020.
Prohotsky D, Zhao F, A survey of top 200 drugs—inconsistent practice of drug strength expression for drugs containing salt forms. J. Pharm Sci. Jan; 101(1):1-6.
Wiedmann T, Naqwi A. Pharmaceutical salt: Theory, use in solid dosage forms and in situ preparation in an aerosol. Asian Journal of Pharmaceutical Sciences. 2016; 11(6):722-734.
Vibramycin. New York, NY: Pfizer; Revised Month. 2016.
Doxycyline. Pub Chem website. https://pubchem.ncbi.nlm.nih.gov/compound/54671203#section=MeSH-Entry-Terms. Accessed April 24th, 2020.
Krout C, Lio P. Tetracyclines: History and Current Formulation Review From a Dermatology Perspective. Practical Dermatology. February 2015. http://v2.practicaldermatology.com/pdfs/pd0215_ClinicalFocus.pdf. Accessed April 24th, 2020.
Savjani K, Gajjar A, Savjani J. Drug solubility: importance and enhancement techniques. ISRN Pharm. 2012;2012:195727. doi:10.5402/2012/195727.