Pharmacology Flashcards
What is a drug?
An external substance that acts on living tissue to produce a measureable change in the function of that tissue
Examples of drugs used in dentistry
Local anaesthetics, antimicrobials, anxiolytics [anxiety], analgesics [post-op pain]
What are some routes of drugs getting into the body
Oral, intravenous, transdermal, subcutaneous, intramuscular, intravenous etc.
Topical defintion
durg is applied to the tissue where it acts
systemic drug definition
drug is applied to the whole organism
parenteral drug defintion
drug administered by injection
transdermal drug definition
drug applied to the skin for absorption
subcutaneous drug definition
drug injected into the tissues of the skin
intramuscular drug defintition
drug is injected into muscle
intravenous drug definition
drug injected into a vein
transmucosal drug defintion
drug applied to the mucosa for absorption [oral environmelt]
advantages and diasadvantages of transdermal/subcutaneous drugs
adv - no first pass metabolism, allergic reactions localised, prolonged action
disadv - very slow onset, drug cost higher, effect varies from person and site
adv and disadv of intramuscular and intravenous
adv - very rapid onset, predicatable plasma levels, no first pass metabolism
disadv - allrgic reactions more severe, short duration of action, access difficulties, no self medication, drug cost higher as purity needed
adv and disadv of oral route
adv - socially acceptable, drug formulation can change onset and duration of action
disadv - slow onset, variable absorption, first pass metabolism
what is first pass metabolism
refers to drug metabolism, whereby a degree of the concentration of drug is greatly reduced before it reaches the site of action
where does first pass metabolism occur
liver
MOA of first pass metabolism
all blood from GI tract drains into the hepatic portal vein and then into liver before being passed to systemic venous system. any drugs absorbed from here will pass liver first and undergo FPM.
FPM when liver function is reduced
amount of FPM is reduced and greater amount of drug will reach circulation, which could have an accumulative and toxic effect. must consider issues when prescribing.
2 types of FPM
inactivation and activation
Bioavailability defintion
the proportion of an ingested drug which is available for clinical effect. extent and rate which the drug enters systemic circulation and accessing site of action
How can bioavailability be changed
dosage form and route of administration. intravenously - 100% bioavailability. oral - depends on food intake, absorption therefore more variable
how are drugs distributed
drugs are dissolved in the blood and transported bound to carriers - usually plasma Albumin
Free drug definition
can act upon target sites and may cause an effect
Bound drug definition
inactive drug as it is not free to enter the tissue
what is drug distribution based on
blood flow and drug ability to dissolve and pass on to different areas. high blood flow areas recieve the most drug
one compartment model
drug injected and available in all tissues
how do drugs enter the brain
through transcellular passive diffusion through lipid membranes into the brain
volume of distribution
different parts of the body are affected differently, some will lipid bind in the tissues, leading to a prolonged effect [like anaesthetic gas]
which organs is drug excretion done through
liver and renal[kidney]
Phase 1 metabolic reaction
reactions will allow drug to change itself
e.g. oxidation, reduction, hydrolysis
Phase 2 metabolic reaction
conjugation of the drug and then secretion
e.g. acetylation, sulphation
Routes of excretion of drugs
Renal through urine. Liver by bile. Lungs by inhaled gas. Small proportions through sweat, tears and saliva.
Renal excretion depends on…
blood flow. disease may impact on ability to excrete blood, keep in mind when prescribing drugs, NSAIDs worsen problem.
What to consider when prescribing drugs?
age of the px [very old or young]
medical hisory, are there any conditions which will worsen or impair drug action
interactions between medications they may already be on
local anaesthetic MOA
block sodium channels, bind and block transmission of pain information.
e.g. lidocaine, articaine
analgesics
given to reduce pain
e.g. ibuprophen, paracetomol, codeine
antibiotics
given to kill infection
e.g. metronidazole, amoxacillin
sedative drugs
nitric oxide (NOS)
midazolam (GABBA) intravenously
still need to monitor airway, pulse, BP etc
emergency drugs
adrenaline for anaphylaxis
inhalers for asthma attacks
heart attacks
