ADRs important in dentistry Flashcards
An additional drug at the same molecular site of action causes either __________ or __________ effect
antagonists
additive (enhanced)
What is an antagonistic effect?
this is when two drugs have opposing pharmacological effects leading to the reduced effectiveness of one or both drugs
Give an example of a drug with an antagonistic effect on another
NSAIDs (tend to increase blood pressure) inhibit the antihypertensive effect of ACE inhibitors or diuretics
What is the possible result of two drugs with the same pharmacodynamic profile?
may result in an excessive respinse of the target tissue and toxicity
What does additive synergy refer to?
effect equals the sum of effects of the 2 drugs
What does enhanced synergy refer to ? Give an example of this
potentiation; the effect is greater
benzodiazepine and opiods could result in respiratory depression
What antibiotic can be prescribed in penicillinase producing bacteria?
-beta lactamase producing bacteria
-coamoxiclav can be prescribed as clavaulanic acid is an inhibitor of betalactamse
What is the effects of pharmacokinetic interactions on drugs?
they alter the concentration of a drug that reaches its site of action
they can increase or decrease the concentration of a drug at the site of action
What are the pharmacokinetic processes that affect the concentration of a drug at its site of action?
- absorption
- distribution
- metabolism
- excretion
What is the effect of penicillin based antimicrobials that can alter the gut flora?
- some of the gut flora is vital for the production of vitamin K
- vitamin K is essential for the producion of clotting factors II, VII, IX, X
- this can result in an increased INR - increased bleeding tendency
What clotting factors have the shortest and longest half lives?
- factor VII has the shortest half life
- factor IX has the shortest half-life
Why are antacids, PPIs and H2 receptor blockers contraindicated for use with antifungals like ketoconazole ?
Azole antibiotics prevent formation of ergosterol
polyene antibiotics disrupt the cell membrane and cause it to become more leaking
Antacid- CaCo3
PPI- omeprazole
H2 receptor blocker ranitidine
- this is because ketoconazole can only be absorbed in acidic conditions therefore their asborption is reduced
Drugs that are bound to plasma proteins are …
inert/inactive
Unbound drugs are active because…
they are free to bind to target receptor binidng sites
Why is the use of aspirin contraindicated for a patient on warfarin?
this is because warfarin and aspirin are predominantly proteins bound and thus compete for the same binidng site on albumin
In the presence of aspirin, warfarin remains unbound and thus there is an increase in its pharmacological effects
There will be an increase in INR and bleeding tendency as a result of this
Why is the use of antibiotic rimfapicin contraindicated with the use of the contraceptive pill?
this is because rimfapicin causes the induction of the CYP450 enzymes in the liver
this leads to an increase in the metabolism of the oral contraceptive pill and therefore its failure
What is the antibiotic rimfapicin used to treat?
- mainly tuberculosis
- brucellosis
- legionnaires disease
- serious staphylococcal infection
There is potential for interaction when two drugs share the sam excretion site. What is the consequence of this?
there is a reduced rate of excretion for one or both drug
this means that the drug is in circulation for longer meaning that the therapeutic effect is prolonged and can potentially be harmful
Why is NSAID use contraindicated with methrotrexate?
they share the same site of excretion (kidneys); this can leads to methotrexate toxicity as there is a reduced rate of excretion of methotrexate
What are the consequences of methotrexate toxicity?
- bone marrow suppression (sore throat, bruising, mouth ulcers)
- liver, pulmonary and GI toxicity
What is the MOA of methotrexate?
inhibits dihydrofolate reductase (DHFR)
which is essential for synthesis of purines and pyrimidines
What is the function of a therapeutic index?
it is a measure of drug safety
gives an indication of how safe the drug is
What is a narrow therapeutic index?
a small reduction or increase of the active drug availability can mean the loss of efficacy or potential toxicity for the drug (a narrow margin of safety)
What does a wide therapeutic index refer to ?
changes in drug availabiliyy unlikely to produce a clinical effect due to a wide margin of safety
Give an example of a drug with a low therapeutic index
digoxin
Give an example of a drug with a higher therapeutic index
amytriptilline
TCA
How are people on drugs with narrow therapeutic indices managed?
they are monitored more regularly
Give examples of lipid regulating drugs
simvastatin
atorvastatin
Give examples of PPIs
omeprazole
iansoprazole