Drug interactions Flashcards
Ketoconazole, Digoxin, and quinolones can be less absrobed by alteration of what?
Gastric pH
How does Metocloperamide affect drug absorbtion?
Increases gastric motility
What is the effect of probenecid on tubular secretion in the kidneys?
- inhibits the anion pump
(methotrexate, penicilin affected)
What is the effect of Cimetidine and Trimethoprim on tubular secretion in the kidneys?
- inhibits cation pump
(procainamide affected)
What is the action of Quinidine, amiodarone, spironolactone, and several CCBs on distal tubular pumps in the kidneys?
- inhibits secretion of i.e digoxin
What effect does urinary pH have on reabsorbtion of weak acids and bases?
(like aspirin and phenobarbital)
low pH - increased acid reabsorbtion
- less base reabsorption
high pH - increased base reabsorption
- less acid reabsorbtion
What action is needed with drug interaction risk rating A and B?
A - no known interactions
B - no action needed
What action is needed with drug interaction risk rating C and D?
C - monitor therapy
D - Consider therapy modification
With drug interaction risk rating X, what is the proper combination strategy?
Avoid combination of these drugs
The combination of Allopurinol with amoxicillin, vit K antagonists, Azathioprine, Mercaptopurin and ACE inhibitors have which classifications?
Risk D (Amoxicillin - risk C)
The combination of B-blockers with the following has which risk class?: Amiodarone, Cimetidine, Insulin,Indomethacin,Fluoxetine, and Paroxetine
Risk C - monitor therapy
The combination of B-blockers with the following has which risk class?:
Clonidine
Risk D (may enchance AV-blocking effect)
Drugs with what effect on p450 should not be used in porphyrias?
CYP inducers induce ALAS and should not be used
Why is it unwise to give aminoglycosides to patients with m.155A>G mutations?
It makes mitochondrial ribosomes in the ear resemble bacterial ribosomes
- > increased ototoxicity chance
What is the mechanism and use of Fomepizole?
blocks alcohol dehydrogenase
use: methanol, ethylene glycol poisoning
What is the mechanism and use of Disulfaram?
- Blocks aldehyde dehydrogenase
use: addiction therapy
What are the effects of alcohol?(5)
- vasodilation
- depressed myocardial contractility
- relaxes the uterus
- enchances GABAa effect
- inhibits NMDAreceptor (learning, memory)
What is Wenicke-Korsakoff syndrome?
- peripheral nerve injury, gait, ataxia, dementia
- caused by thiamine deficiency
(many are left with Koraskoff’s psychosis despite treatment)
What is the effect of chronic vs acute alcohol use on the CYP450 system?
chronic - induces P450
acute - decreased enzyme activity
What happens if alchohol is combined with other CNS depressants, vasodilators, or oral hypoglycemics?
- additive CNS depression
- potentiates effect of vasodilation or hypoglycemics
What drugs are used to treat alcohol withdrawal syndrome?
Benzodiazepines:
- long acting preferred, but may accumulate in liver
- short acting if liver disease
(lorazepam, oxazepam - renal excretion)
- Drugs are tapered slowly, and thiamine should always be used
What drugs are used to treat alcoholism?(3)
Naltrexone - opiod antagonist
Acamprosate - NMDA antagonist, GABAa agonist
Disulfaram - ALDH inhibitor
