Pharmaceutics in Broad Overview

Created on Thu, 09/07/2017 - 17:54
Last updated on Thu, 09/07/2017 - 18:14

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This chapter answers parts from Section A(i) of the 2017 CICM Primary Syllabus, which reads cryptically "A more detailed knowledge would be expected for more commonly used drugs.". For whatever reason, the examiners attribute an L1 level of importance to this criterion ("core areas... detailed knowledge and comprehension..." etc).  At the time of writing, the old 2011 curriculum (which is rapidly becoming obsolete) makes more sense than this by virtue of its use of classical terms like "outline" and "define" to describe the college's expectations.

So, what could be meant by "a more detailed knowledge"? One makes a series of intuitive leaps and assumptions when writing an exam revision summary for something so ill-defined. It is necessary to guess the college's intentions, and the guess might be hilariously wrong, leading trainees into the wild woods of irrelevant apocrypha.  However, that is to be expected from an unreliable non-peer-reviewed online resource; you get what you paid for. Moreover, there have never been any "pharmaceutics" questions in the written paper as far as this author can see, except for Question 20 from the second paper of 2012, which asked about enantiomerism.

With these ill-defined expectations in place, what should the time-poor exam candidate reads to get "a more detailed knowledge" of pharmaceutics? Particularly for more commonly used drugs? What would even be the definition of pharmaceutics? 

Definition of pharmaceutics 

The standard textbooks from the college recommended reading list do not seem to have much of a definition for this term (it only appears in contributors' titles if one does a search in Goodman & Gillman). Fortunately, there's Wikipedia:

"Pharmaceutics... is the discipline of pharmacy that deals with the process of turning a new chemical entity (NCE) or old drugs into a medication to be used safely and effectively by patients. It is also called the science of dosage form design."

To rephrase, pharmaceutics is the study how to best present the pure drug molecule in order to achieve the therapeutic goal.  Thus, a Level 1 understanding of this matter for commonly used drugs will require the trainee to have some level of comprehension regarding the drug's presentation, the excipients presented with it, its compatibilities, and the various tricks which might be used to improve its effectiveness. By extension this might include such manipulation of elimination as giving probenecid to patients on cephazolin therapy (it competes with cephazolin for excretion).  

To put it even more simply, pure drug is usually a crystalline white powder which might be only required as a miniscule microgram-level speck in order to be effective, and the science of pharmaceutics is concerned with turning that raw chemical into a medication, ensuring that this miniscule speck is safely delivered to its target receptors without destroying the surrounding organism in the process.

Scope of the topic

Going off the definition offered above, one can see how it might be insane to confine all information for all commonly used drugs in one chapter. Instead some elements of this will be explored for each specific drug, digressing briefly on the reasons as to why it has been presented and formulated in precisely this way. 

In general, pharmaceutics includes:

  • Presenting the drug in a usable and durable form
    • Bulking agents
    • Stability modifiers
    • Preservatives
  • Changing the physico-chemical properties of the drug to ensure its delivery
    • Complexing the drug
    • Changing its solubility
    • Modifying the absorption mechanisms, eg. in controlled-release formulations
  • Improving the safety of the drug to the person administering it
    • Making a cytotoxic drug less volatile
    • Presenting a radioactive isotope in  shielded packaging
    • Ensuring the ampules break correcly without lacerating fingers
  • Controlling the risk of incorrect drug administration, eg
    • Labelling the packaging and making it sufficiently distinct
    • Naming the drug unambiguously
    • Appropriatly using warning labels and cautionary signs
  • Improving the tolerability or appeal of the drug
    • Flavours and colours, eg. syrup for children
    • Easily swallowed pill coating
    • pH-adjusted intramuscular injectable formulation
    • Cosmetic appearance of the packaging

Some of this is covered in more detail throughout other chapters within this section.

 

References

Aulton, Michael E., and Kevin MG Taylor, eds. Aulton's Pharmaceutics E-Book: The Design and Manufacture of Medicines. Elsevier Health Sciences, 2017.

Banker, Gilbert S., Juergen Siepmann, and Christopher Rhodes, eds. Modern pharmaceutics. CRC Press, 2002.

Bernardo, Peter D., and Emanuel J. Russo. "Pharmaceutical sciences—1968. A literature review of pharmaceutics.Journal of pharmaceutical sciences 58.7 (1969): 777-812.