Principles of Pharmacological Practices
- start low and go slow
Pharmacokinetics (Kinetics means movement): ADME (absorbed, distributed, metabolism, excreted)
Factors: Membranes and barriers (phospholipid cell membrane)
Passive diffusion (move from higher concentration to lesser gradient)
Poor blood flow limits diffusion
GI motility (high fat meals can delay gastric emptying and decrease delivery)
1st pass affect- degraded by liver before central circulation
Drug binding (proteins). Bound proteins cannot enter cells freely
( must unbind and become free drug and non-ionized)
Liver metabolizes, kidneys excrete
½ life: time required for drug to be ½ eliminated from the body
Pharmacodynamics: what drug does to body
Drug interacts with specific body receptor and sets a chain of events into action
Drug acts like a “key” and unlocks activity of receptor
Ligand: any chemical that interacts with a receptor
Receptor: site of drug action
Prodrug: drug that is transformed from inactive form to active metabolite in the body
What affects pharmacokinetics and pharmacodynamics?
- patient variables (body type, weight, diet, ethnicity and genetics
- disease states can change organ responses (ie: liver disease)
- age (neonates may have immature systems; metabolizing enzymes might not be functional)
- children metabolize faster
- women higher % body fat
- ethnicity differences
Other considerations:
- pH (acidity of stomach), which is why some drugs can’t be given with H2 blockers
- lipophilic drugs pass through lipid membranes of cells easily (but need to be changed
to become water soluble to be excreted)
,Isoenzyme System
- P450 (class of enzymes)
CYP1A2
CYP2C9
CYP2C19
* CYP2D6 responsible for 30% of drug metabolism (10% Europeans lack)
CYP2E1
* CYP3A4 responsible for 40% of drug metabolism
Polymorphism:
https://i0.wp.com/selfhacked.com/wp-content/uploads/2016/10/CYP_metabolizers.jpg?resize=700%2C408&ssl=1
Prodrug Examples: prednisone converted to prednisolone in liver
fosphenytoin converted to dilantin
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,Pain Management
Types:
-. Nociceptive
Somatic (muscle/skin/bone) Visceral (organ pain such as pancreatitis/appendicitis)
- Neuropathic (from CNS)
Peripheral (diabetes neuropathy) Central (migraine, multiple sclerosis, spinal cord)
acute pain- sudden onset
chronic pain- exists beyond normal expected time frame
Noxious Stimuli causes primary sensory neuron to travel up dorsal horn of spine and then to brain
https://hillsphysiotherapy.com.au/wp-content/uploads/2017/10/Pain-Pathway.jpg
Pain Assessment- OPQRST
Always SUBJECTIVE
- numeric pain scale (0-10)
- simple descriptive pain scale (mild/mod/severe/worst pain)
-visual analogue (no pain………bad pain)
, Rest, heat/cold, imagery, relaxation
Acetaminophen
NSAIDS
Muscle Relaxers
Lidocaine patches
TCAs/SNRIs (duloxetine)
Gabapentin
Opioids
Naltrexone (antagonist blocks euphoria)
https://www.researchgate.net/profile/Anne-Olesen-
2/publication/268335204/figure/download/fig1/AS:646490506678273@1531146756166/WHOs-pain-ladder-If-
pain-occurs-there-should-be-prompt-oral-administration-of-drugs-in.png
Gate Theory of Pain Control: Connection between body and brain. Sensations pass through the spinal
cord via gates to get to the brain. Certain things can close the gait and not permit pain impulses to travel
(massage, TENS, heat/cold). This is a type of modulation.
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Antimicrobials- identify the causative agent is key
Penicillins: most unstable in acid (therefore given parenterally, IV)
- most excreted by kidneys