Intro to pharmacology - route of admn & basics Flashcards
Pharmacokinetics - what is it ? … mechanism ?
What the body does to the drug
- absorption
-distribution
-metabolism
-excretion
Pharmcodynamics
what drug does to the body
includes : mechanism action + effect of the drug
what constituets pharmcotherapy
prevention
treatment
diagnosis
What are the principles in drug administration
Safety
Rationalizing
montioring
individualizing
What is rationalisation of drug? & principles
drugs given match the clinical need
dosage must meet the individuls requirement
for an adequate period of time
at low cost for both community & patient
(effectiveness, safety, and cost-effectiveness of various drugs to make informed decisions about their use.)
Effects of irrational prescription
Delay in cure
More adverse effects
loss patients confidence
Lowering health standards
Causes of irrational prescription
Underprescribing - not enough dosage
Incorrect prescribing
Over prescribing
How to choose best way to treat a condition?
-is drug therapy indicated ? and if so
-which drug is best for condition?
-which route is most effective ?
-which formulation ? capsule , rectum , serum
-Which dosage regimen? - during the night , after meals , day , how many times in a day.
What is P-drug ( personal drug)
Drug that you have become familiar with and choose to prescribe regulary.
- all categories of drugs there is a p-drug (prototype drug)
Advantages of P-drugs
Convinent
confidence
master easily
predictable
less complications
simpler healthcare management
What are the major classification of routes of drug administration
Enteral
Paraenteral
Topical
Describe Enteral & give examples
Def : delivery of drug through GIT(then absorbed) from the mouth
Example : oral , sublingual , rectal
Define Parenteral & give examples
Def : delivery of drug directly into body through IV
Example:
- intravenous/intraarterial
- subcutaneous
- Intramuscular
- intradermally
Define topical and give examples
Def: apply the drug directly onto the surface of skin / mucous membranes - allowing for local action of drug on the specific area applied
Examples
- Nasal(spray) , auditory(drops) , mucosal , conjunctival
- Vaginal & urethral
- Inunction (ointment , cream ) & dermal
What are facotrs that govern the route of drug administration ?
1.Physical & chemical properties of drug
2.Rate & extent of absorption
3.effects of digestive juices - can it withstand
4.site of desired action
5.rapidity of desired response
6.accuracy of dosage
7.condition of patient - child cannot swallow tablets
Advantages & disadvantages of Oral
Adv
1.Safe
2.Convenient
3.Economical
4.Usually good absorption
5.self administered
6.Painless
Disadv
1.Slow absorption
2.slow action
3.irritable & unpalatable(not pleasant) - can spit it
4.some drugs destroyed
5.First - pass effect
Sublingual
-Location
-Advantages & Disadvantages
Site : under the tongue
Adv
1.Economical
2.Drug absorption quick - dissolved & absorbed directly in circulation
3.First pass avoided
4. self administered
5.quick termination - spit off
Disadvantages
1.Unpalatable & bitter drugs
2.Irritation of oral mucosa ( cause mouth ulcers)
3. Large quantities not given
4. High molecular weight drugs not absorbed - due to small spaces itd have to pass through
Example of drugs administered sublingually (systemic & local)
Systemic use
- Isosorbide dinitrate
- nitroglycerine
- Nifedipine
Local
- antiseptic lozenge
Advantages & Disadvantages of Rectal route
Advantages
1. Used in children
2. Little/no first pass effect (avoids 50%) - majority of drug absorbed
3. Used in vomiting /unconsious
4.Higher conc can be given
5.Can use gastric irritants
Disadvantages
1. embarrasing
2.inconvient
3.Absorption is slow & erratic
4. Irritation/ inflammation of rectal mucosa
Examples of drugs given via rectal route . ( local & systemic)
Local
1.Dulcolax
2.Glycerine suppository
3.Enema - dissolve in oral mucosa
4.Ointment
Systemic
1.Aminophylline
2.Indomethacin suppositories
Intradermal route
- Site
- advs & disadvantages
- example
Site : outer layer of skin
Adv
1.Used for testing sensitivity to drugs
2.high vascularity of dermis
Disadv
1.Painful
2.Amount of drug administered is small
3. Slow adsorption
4.Skin irritation
Example : BCG vaccine , allergic sensitivity test ,tubercullin test
uses tuberculin syringe 4
Subcutaneous
Site: under skin ( deeper than intradermal)
Sites : gluteal , thigh , shoulder , back
Advs
1.Smooth but slow absorption
2.Depot injections , implants
Disadvantages
1.only Small vol (1ml )
2.irritant drugs = lead to necrosis
3. not suitbale in shock (vasoconstriction + redistibution of blood)
Examples for subcutaneous route
Local : local anaesthetic
Systemic: insulin
intramuscular
major sites
advantages & disadvantages
Major sites : deltoid , gluteus , vastus lateralis
Advantages
1.absorption reasonably uniform
2. rapid onset action
3. mild irritants can be given
4. first pass avoided
4.Gastric factors can be avoided
DIsadvantages
1. only up to 10ml given
2.local pain & abscess
3.Expensive
4.Infection
5.Nerve damage (sciatic nerve )
Intravenous route advantages
1.Bypass first pass metabolism (100%)
2.quick onset of action
3.unccoperative & unconsoiious patients .vomiting & nausea
4. drugs of hypertonic solns & irritants
5.LArge volumes
6.Amount of drug can be controlled accurately
Disadvantages of intravenous
- Required antiseptic conditions - to prevent infection in blood
- specialised skills
3.painful - cannot be recalled - wrong dosage is a wrong one
- cause air embolism - lead e.g heart failure , pulmonary embolism
- cannot give suspensions , oily drugs & depots
- can cause extravastion / thrombophlebitis
What is extravasation
escape of fluid from a blood vessel to surrounding tissue during IV cannulisation
- painful & harmful
Definition of Thrombophlebitis
irritation of vein during cannulation causing inflammation and leading to clot.
Intra-arterial
Site
advantage
Disadvantage
example
Site: lumen artery
Advantage:
-greater conc of drug can be delivered
Disadvantage
-Expertise
-Asepsis
Example : radiopaque contrast for coronary angiopraphy & cerebral angiography
Intraperitoneal
Site
Advantages & Disadvantages
Examples
Site : peritoneal space
Advantages
- rapid absorption (due to large SA)
Disadvantages
- Painful
- risky
- adhesions
-peritonitis
example: dialysing fluid ( renal failure)
Intrathecal(intraspinal)
Site
Advantages & disadvantages
Example
Site: subarachnoid space
Advantages
- bypass Blood brain barrier
Disadvantages
- asepsis
- expertise
- painful
- risky
Example : radiopague contrast media , xylocaine injection
Intramedullary
Site
Advantages & Disadvantages
Examples
Site : tibia
Advantages : rapid onset of action
Disadvantages
- strict asepctic conditions
- expertise
- painful
- risky
Examples : Emergency fluids in children
Intracardiac injection
site
Examples
Left 4th intercostal space into heart muscle
Example : cardiac arrest
Intraarticular route
site
advantages & disadvantages
Example
Site: directly into joint space
Advantages: high conc in localised area
DIsdavantages:
- asepsis
- joint damage
- pain
Example :
- Hydrocortisone
- Gold chloride
Transdermal route
what ?
advantages
what? absorption of drug through skin for systemic action via a patch
Advantages
1. stable blood levels - ( a particular mg permin)
2. no first pass metabolism
Disadvantages
3. drug must be potent or patch will become too large
potent meaning - administered effectively through a transdermal patch, the drug needs to be highly concentrated or potent. this is because, in a transdermal patch, the drug is absorbed through the skin over an extended period. If the drug is not potent, it would need to be present in large quantities in the patch to achieve the desired therapeutic effect, which would result in a very large or bulky patch.
What is first pass effect
term used for hepatic metabolism of drug when it is absorbed from gut & delivered to liver via portal circulation
The greater the first pass effect , the lower the bioavailability of the drug
