Introduction to pharmacology

External References
Transcript

Content Reviewers:

Rishi Desai, MD, MPH

Pharmacology is the study of medications, or chemical compounds, which interact with various living systems, from tiny molecules to cells, to tissues and whole organisms in order to produce a certain effect.

Every day, more and more new medications are designed to fight diseases, from infections to cancer, heart failure, and depression.

But the process of developing a new medication can take a lot of time and money, and it typically consists of three phases.

First, there’s the discovery phase, in which a candidate compound is picked out as a possible therapeutic agent for a specific disease.

Then, there’s the preclinical phase, during which this compound is tested on cell cultures and animals, like mice and rats, mainly to see if it causes any serious harm.

And, finally, during the clinical phase, the compound is tested first, on healthy human volunteers, to make sure it’s safe, and finally on individuals suffering from that disease, to find out if it’s indeed effective against this disease.

If all this goes well- congratulations! We’ve got a new medication!

This medication will have at least three names- a chemical one, describing its chemical structure and used mostly in scientific studies, like N-acetyl-p-aminophenol, a generic name, which is usually a shortened version of the chemical name and is mostly used by health professionals, such as paracetamol or acetaminophen, and one or more brand or trade names, given by the pharmaceutical companies that make the medication, such as Panadol or Tylenol.

Now, every medication contains a precise amount of the active ingredient, called the dose, which is often as little as 5 milligrams - that’s less than a grain of sand.

Since that’s too small to even handle, it’s usually combined with inactive substances, like fillers, binders, and lubricants that serve to fill out the medication and make it more convenient to use.

Together they get manufactured as a chemical preparation, like a pill, solution, spray, or ointment.

According to the form of the chemical preparation and the part of the body being treated, it can then be administered through various means or routes, like swallowed by the mouth- orally, inhaled into the lungs, injected into a vein- intravenously, into a muscle- intramuscularly, sprayed into the nose- nasally, or applied upon the skin- cutaneously.

Alright, now, once administered, the medication starts interacting with the body.

This interaction can be broken down to pharmacokinetics and pharmacodynamics.

Pharmacokinetics refers to the movement and modification of the medication inside the body.

In other words, it’s what the body does to this medication. So, once the medication gets administered, it first has to be absorbed into the circulation, then distributed to various tissues throughout the body, metabolized or broken down, and, finally, eliminated or excreted in the urine or feces.

You can remember this as ADME- Absorption, Distribution, Metabolism and Excretion.

Sources
  1. "Systems pharmacology and genome medicine: a future perspective" Genome Medicine (2009)
  2. "Goodman and Gilman's The Pharmacological Basis of Therapeutics, Twelfth Edition" McGraw Hill Professional (2010)
  3. "Katzung & Trevor's Pharmacology Examination and Board Review,12th Edition" McGraw-Hill Education / Medical (2018)
  4. "Rang and Dale's Pharmacology" Elsevier (2019)
  5. "Systems Pharmacology: Network Analysis to Identify Multiscale Mechanisms of Drug Action" Annual Review of Pharmacology and Toxicology (2012)
  6. "Pharmacokinetic-pharmacodynamic relationship" Ann Rech Vet (1990)
  7. "Duration of drug action" Am Fam Physician (1980)