Drug questions Flashcards
Cisplatin is given at night. Why?
That is when urinary output is maximal and reduces renal toxicity.
Glucocorticoids are given in morning, why?
This is when cortisol production naturally peaks. This will reduce some side effects of prolonged hyperglycemmia.
Statins are given at night, why?
This is when cholesterol synthesis peaks, because in most people, they are fasting at this time.
How can ASA, which has t1/2 = 4 hours, exert an effect that lasts for 7 days?
It is an irreversible COX inhibitor, so the effects last as long as the platelet, about 7 days.
How is Cromolyn (intal) given and why?
Inhalation, because it has a bioavailability of <10% orally. An asthma med
What to worry about with Digoxin absorption
Dietary fibers bind to Digoxin, reducing absorption.
What to worry about with Synthroid absorption
Synthroid uses amino acid transporters to move from duodenum to blood. If you eat protein, proteases in the duodenum cleave these into their constituent a.a. and now synthroid has competition for the a.a. transporters.
Explain how L-Dopa + Carbidopa works
L-Dopa enters the SNS and crosses the BBB. It is then converted into Dopamine in the brain, but Carbidopa (which can’t cross the BBB) prevents its conversion to Dopamine in the body, preventing arrhythmias, about allowing the treatment of Parkinsonism.
Differences between Heparin and Warfarin with regards to placenta?
heparin has a Molecular Weight > 1000, while Heparin’s is only 500. Warfarin can pass through the placental barrier and is fetal toxic.
Can succinylcholine pass the placenta?
No, because it is highly polar
Can thiopental pass the placenta?
Yes, because it is highly lipid soluble and can cause fetal sedation/apnea.
What is relationship of drug half-life to PBP?
Epi weakly bound = 15s
Tolbutamide 96% bound = 6 hour
What is the warfarin/ASA interaction?
Typically, Warfarin is 99% bound to PBP.
When ASA is taken, it displaces some Warfarin from PBP, increasing [free] and intensity of action/adverse effects.
What is relationship between Sulfonamide abx and bilirubin?
Normally PBPB bind bilirubin in neonates. When Sulonaminde abx are given, the abx competes with bilirubin for PBP and increases its [free] and it enters the CNS producing toxic effects.
How would cirrhosis affect Ambien?
Ambien is 92.5% bound. In cirrhosis, make fewer PBP, so drug would be less bound and intensity of response/ toxicity would increase.
What is important about tetracycline?
It is deposited into developing bone and teeth, discoloring them.
What interaction does quinidine and digoxin have?
Quinidine can displace digoxin from muscle, increasing dig toxicity.
Give 4 drug examples of metabolism.
- Inactivation of Procaine into PABA.
- Increasing therapeutic effect of codeine into morphine.
- Activation of prodrug fosphenytoin into phenytoin.
- Increased toxicity of acetaminophen into metabolite.
What is classic example of first pass effect?
NTG, that’s why give it SL.
Hydrolytic enzymes
Pseudocholinesterase hydrolyzes succinylcholine and procaine, metabolizing them.
Another First Pass drug
Propranolol, so oral dose is much higher
2 Prodrugs
Loratadine and naproxen
Acetaminophen metabolism
Phase I: CYP reaction produces a toxic metabolite.
Phase 2: This metabolite is quickly conjugated with glutathione.
In OD situations, glutathione is depleted and [metabolite] increases!
How does Mucomyst help in acetaminophen OD?
Stimulates synthesis of glutathione.
CYP inducers
- Phenobarbital
- Tolbutamide
- Phenytoin
- Cigs
- chronic EtOH
- charcoal cooked food,
- cabbage
- Factory workers exposed to nitrates respond poorly to ntg
- some insecticides in farm workers
Dicumarol + Phenobarbital
Dicumarol is an anticoag given to pts that have had strokes. If they then have seizure, we give them phenobarbital (a CYP inducer). This increases metabolism of dicumarol and they can clot more, so must up dose.
CYP inhibitor
cemetidine inhibits the metabolism of estradiol, causing gynecomastica in men
Why add sulbactam to PCN drugs?
It is an inhibitor of beta lactamases which metabolize PCN
Why take disulfiram if an alcoholic?
It inhibits the complete metabolism of EtOH, allowing acetaldehyde to accumulate, which causes vasodilation, HA, n/v
Explain how chemical antagonism works
Protamine (a positively charged molecule) binds to Heparin (a negatively charged molecule) preventing Heparin from binding to clotting factors.
Explain how physiological antagonism works?
Glucocorticoid therapy causes hyperglycemia that can compromise the effect of insulin.
