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BCACP > Pharmacokinetics & DI > Flashcards

Pharmacokinetics & DI Flashcards

1
Q

Pharmacokinetics is?

A

What the body does to the drug.

Absorption, distribution, metabolism and excretion

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2
Q

Pharmacodynamics is?

A

What the drug does to the body.

Relationship between drug concentration at site of action and both therapeutic and adverse effects.

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3
Q

Zero order kinetics

A

Constant amount of frug (mg) removed per unit of time regardless of how much drug is in the body

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4
Q

First order kinetics

A
  • Most drugs

- Constant PERCENT of drug removed per unit of time

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5
Q

Michaelis-mente Kinetics

A
  • Saturable kinetics
  • Starts as 1st order and as concentration increases above Km (concentration at which rate of metabolism is half max) rate of metabolism becomes mixed (first and zero), at even higher doses it becomes zero order

Example: phenytoin, theophylline, voriconazole

-Phenytoin has saturable kinetics even at therapeutic drug concentrations. Do small dose increase by 30-50mg if concentration >7mg/L (RR10-20 mcg/ml). In other words steady state concentration becomes very high causing toxicity.

Sms of phenytoin toxicity: slurred speech, fatigue,

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6
Q

Half life and steady state

A

T1/2= 0.693/ke
Ke= Cl/Vd
Cl= (FxDose)/AUC
Vd=dosegiven/concentration

-Elimination half life: time for drug concentration to decrease by 50%. Depends on drug concentration in first order kinetics.
Steady state: rate if drug intake =rate of elimination. -Takes 5 half lives in first order kinetics with no loading dose
-5 lives to eliminate more than 95% of drug

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7
Q

Warfarin metabolism?

Interacts with which inducers/inhibitors and what is the effect on INR?

A

CYP2C9
Strong inducer: Rifampin, dose of warfarin will have to be increased 100-300% time

String inhibitor: amiodarone, decrease warfarin dose by 30to 50%
How long does it take to see full effect of this interaction?

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8
Q

Codeine/tramadol is a prodrug off morphine and is activated by which enzyme?

A

CYP2D6

  • Not inducible enzyme
  • Ultra rapid metabolized (UM) results in increase morphine»>more analgesia and risk of respiratory depression
  • Inhibition (fluoxetine,paroxetine) results in decrease codeine conversion to morphine»>less analgesia
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9
Q

Grouping of DI:

Usual Inducers?

Usual inhibitors?

A

Cyp3A4 Inducers:

  • anticonvulsants (carbs, Oxa, eslicarb, phenytoin, phenobarbital)
  • rifampin, rifabutin, rifapentine
  • smoking
  • primidone
  • simeorevir
  • St. John’s wort

CYP 3A4 Inhibitors:

  • azole antifungals
  • amiodarone and dronaderone
  • diltiazem, verapamil
  • quinidine
  • Microlides( not azithromycin)
  • PI IHV drugs and ritonavir
  • grapefruit juice
  • Cimetidine, cyclosporine, cobicistat
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10
Q

Substrates of CYP3A4?

A

Anticoagulants: apixaban, riva, R warfarin)
Statins: atorva, sinva,lova) use Rosu

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11
Q

Glucuronidation DI:

UGT1A1 enzyme drug interaction example?

A

Raltegravir concentration would decrease if strong inducer rifampin used.
How to fix? Increasing dose of Ral to 800mg BID?

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12
Q

Amiodarone DI

A

Digoxin and warfarin doses need to be decreased (30 to 50%) when amiodarone started

Cyp3A4

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13
Q

Digoxin interacts with what Disease state?

A

Decline in renal function and HYPOkalemia (regardless of digoxin game level)
Amiodarone

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14
Q

Grape fruit juice interacts with?

A

Inhibit 3A4
>1.2L/day Intake

Avoid with: Silva,lova,nifedipine,tacrolimus

Ticagrelor increased bleeding risk

Other cyp3A4 substrates

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15
Q

Opioid analgesics DIs

A

-Fentanyl, hydrocodone, oxy, methadone

Are Cyp3A4 substrates

Interaction with inhibitors of enzyme will lead to resp depression

Removal of inducer would cause increased drug levels it dose is not adjusted

Avoid with inhibitors:
Oxy has BBW
Methadone has a warning

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16
Q

Warfarin drug interactions that increase bleeding risk

A

NSAIDs,SSRIs, SNRIs, ginkgo (no efectbon INR), fish oils, vitam E, willow bark

5Gs that can increase bleeding risk:
Ginkgo
Garlic
Ginger
Glucosamine 
Ginseng
17
Q

Drug interactions that cause hyperkalemia risk

A

Aldosterone blockers

  • Avoid use if baseline k is >5
  • Avoid use with concurrent NSAIDs

Additive accumulation: ACEs/ARBs, aliskerin, amiloride,trianterene, salt substitutes, drospirenone OC,
Other: tacrolimus and cyclosporine, canaglifozin, bactrim, pentamidine

Tx of chronic hyperkalemia:

  • hold or reduce RAAS drugs
  • Petiromer (valtessa) PO
  • sodium zirconium cyclosilicate (lokelma) fastest response
  • k binders may allow to keep dose of RAAS agents needed for indication (e.g heart failure) at recommenced dose.
  • Avoid periods of fasting to prevent insulin response. -avoid NSAIDs
  • use diuretics with RAAs agents helps
18
Q

Max dose of simvastatin when taking amiodarone

A

20 mg

19
Q

What anticonvulsants do not inhibit it induce cyp?

A

Leve
Lamo
Gana
Pregaba

20
Q

What anticonvulsants are not a substrate or cyp450?

A 
Leve
Lamo
Gaba 
Pregaba
Oxacarb 
Eslicarb 
Topi
Rufinamide
21
Q

Anticonvulsant inducers will decrease dose of what 3A4 substrates?

A 
Amiodarone, dronaderone 
Antiretrovirals: PI, NNRTIs
Clozapine 
COC
Cyclosporine
Digoxin
DOACs: riva,apixa, edox,
22
Q

What 2C9 and or/2C19 inhibitors will increase PHY concentration?

A 
Amiodarone 
Cenobamate
Fluconazole
Fluoxetine
Omeprazole
23
Q

What anticonvulsants are sting Cyp inhibitors?

A

Valproate

Cannabinoid

24
Q

What anticonvulsants are strong inducers?

A

PHY-zero order kinetics
PHB
CBZ-autoinducer

Mod inducers:
Oxa
Eslicarb (>1200mg)
Topi (>200mg)

Cenobamate: both inducer and inhibitor

25
Q

Lamotrogine DI- hepatic megabolims glucuronic acid conjugation

A 
Levels decrease by:
PHenytoin
Phenobarbital 
Carba
Estrogen

Increased with:

Valproate

26
Q

COC oral concentration decreased by?

COC affect concentration of which anticonvulsant?

A 
1- Strong inducers: 
Clobazam
Eslicarb 
Oxcarb 
Perampanel
Rufinamide
Topi
Cenobamate

Use: IUD, implant, Depo provera

2- Lamotrigine levels decreased by 40-60% by estrogen component of COC.

BCACP (6 decks)

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