Wednesday, October 2, 2013

Medicinal Chemistry (aka Drug Structure) - the hardest course in pharmacy school

I'm  taking an exam for my "Chemical Principles of Drug Action III" class later today (5-7pm)...I thought I'd ask for prayers and also bore you with some tidbits about med chem and perhaps show you a part of what we learn in pharmacy school.

This is our 3rd course in the med chem sequence, and this quarter we are covering Infectious Disease Topics - aka the structure and function of antibiotics. Today's exam covers the following classes of antibiotics: penicillins, cephalosporins, carbapenems, well as macrolides, ketolides, and chloramphenicol.


 The class consists of pretty much applying everything we know about chemistry (especially organic chemistry) to drug structure, and thus drug function. In other words, it answers the question: what about this drug's chemical structure makes it kill bacteria the way it does and what about the structure gives this medicine its side effects (upset stomach, nausea, diarrhea?). Through learning the structural features responsible for both the action and the side effects of a medication, medicinal chemists can  tweak the structure in lab and try to come up with a medication that is the most potent with the least amount of unwanted side effects.

 For example, on the right, you see penicillin G. You only see this one used in hospitals, not in community pharmacy, because it can only be given IV (intravenously) or IM (intramuscularly). It cannot be formulated into oral use (tablets, capsules, suspension) because it lacks a certain "electron withdrawing" functional group on the highlighted portion of the drug. The only penicillin you see in community pharmacy is Penicillin V, which is a little bit different structurally.

To contrast this, look at Amoxicillin. (This is not the full structure, by the way, just one of the functional groups). Everybody has probably at some point of their life taken Amoxicillin, or its sister Augmentin....and we all know that it can be taken in the form of tablets, capsules, and liquid for oral use. The whole reason behind that is the NH2 (amino) group highlighted here, which is electron withdrawing (it loves electrons) and causes Amoxicillin to be stable in the very low, acidic pH of the stomach. Also, the OH (hydroxyl) group highlighted increases the speed of absorption of amoxicillin from the stomach, thus decreasing the potential for gastrointestinal side effects such as nausea and diarrhea. However, most people will still experience some level of nausea if they take it on an empty stomach, so it is recommended to be taken with food or milk. I know this is boring to all people that are not science / chemistry nerds like me, but at least I can introduce you to the general concepts of how drugs are developed and improved...all based on chemistry! 
I hope you're not asleep yet!

And above you see some mechanisms of how bacteria become resistant to these antibiotics.

Well, I'm off to study some more drug structures now.
Then I am off to my pharmacotherapeutics lecture, followed by a 2 hour workshop on thyroid disorders (and how to treat them), followed by this lovely exam. (Oh yeah, and the therapeutics lecture is on I'll let you know how that goes...I'll probably be ripping my hair out by the end of it :-O ) Long day ahead of me!

If anyone has any drug-related questions, let me know!
Although I'm still learning, I'll give it my best shot. I've worked at a community pharmacy for 3 years now so I do have hands-on experience with the most common drugs and problems...I also have access to really powerful databases through the university to look up any drug information I may need.

Hope everyone has a great day!

1 comment:

  1. Wow...That looks like complicated stuff! I admire you for undertaking such an intense program and sticking with it!