Drug Elimination Flashcards

1
Q

Drug elimination is essential no matter the route of administration. T/F

A

True

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2
Q

What is elimination?

A

The irreversible removal of metabolized and unmetabolized xenobiotics from the body.

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3
Q

What are the types of elimination?

A

Systemic elimination

Pre-systemic elimination

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4
Q

What is systemic elimination?

A

Drug eliminated form systemic circulation.

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5
Q

What is pre-systemic elimination?

A

Drug eliminated before entry into systemic circulation. Drugs eliminated by first pass effect.

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6
Q

What are the routes of elimination?

A
Kidneys/Urine
Bile/Feces
Lungs/Exhalation
Breast Milk
Skin/Sweat
Tears
Hair
Saliva
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7
Q

What is the primary excretory organ?

A

Kidneys

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8
Q

What is the primary route for polar drugs and metabolites to be eliminated?

A

Kidneys

Non-polar drugs(phenytoin) are subject to tubular reabsorption.

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9
Q

What is the primary route for lipid-soluble drugs plus less polar drugs and metabolites to be eliminated?

A

Bile/Feces

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10
Q

What is the primary route for inhaled anesthetics to be eliminated?

A

Lungs

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11
Q

Why is breast milk clinically important even though it is not a major route of elimination?

A

Because drugs can be passed from mother to nursing infant.

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12
Q

Why is skin/sweat, saliva, or hair clinically important even though it is not a major route of elimination?

A

It may be used for monitoring or testing.

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13
Q

Why is tears clinically important even though it is not a major route of elimination?

A

It may be of concern to contact lens wearers.

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14
Q

What test can be used for hair?

A

Psychemedics PDT-90 test to test for marijuana, ecstasy, cocaine, crack, heroin, methamphetamine, phencyclidine (PCP or angel dust) for up to 3 months.

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15
Q

What are examples of drugs that are eliminated through the kidneys?

A

Vancomycin, atenolol, ampillicin (polar drugs with CA and amide)

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16
Q

Renal excretion is affected by?

A
Kidney disease
Glomerular Filtration Rate
Extent of back diffusion (unionized drug) or reabsorption
Active Tubular secretion
Tubular pH
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17
Q

What needs to be taken in to consideration when a patient has chronic kidney disease (CDK), HBP, or diabetes?

A
Certain drugs dose may need to be adjusted.
Aminoglycoside antibiotics (Amikacin, Tobramycin)
Cephalosporin antibiotics (Ceftazidime, Procainamide)
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18
Q

What elimination occurs through glomerular filtration?

A

Low MW (

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19
Q

What elimination occurs through tubular reabsorption?

A

Can be affected by pH change

Un-ionized drug is reabsorbed into plasma (Mostly passive back diffusion)

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20
Q

What elimination occurs through tubular secretion?

A

Kidney & GI OATPs, POTs, PGPs, MRP2 - are involved in Secretion and reabsorption.
Inhibitors/Inducers will impact drug elimination.

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21
Q

_____ inhibits kidney OATPs which slows elimination of ________.

A

Probenecid inhibits kidney OATPs which slows elimination of Penicillins.

22
Q

What are the transporters in the SLC (solute carrier protein) superfamily?

A

Organic anion-transporting polypeptides (OATPs)

Proton-dependent oligopeptide transporters (POTs)

23
Q

What are the transporters in the ABC (ATP-binding cassette) superfamily?

A

P-glycoprotein (PGP/MDR) efflux Pumps
Multidrug Resistance (MRP) efflux Pumps
Breast Cancer Resistance Protein (BCRP)

24
Q

elimination of ionizable drugs/metabolites can be affected by ______.

A

urinary pH

25
Q

Acidification causes elimination of acidic drugs to ______ while the elimination of basic drugs _______.

A

Acidification causes elimination of acidic drugs to decrease while the elimination of basic drugs increases.

26
Q

What is pH trapping?

A

Impact drugs that are passively eliminated in its unionized form. Drug ionizes in urine. Ionized drug is difficult to be reabsorbed, ergo it is “trapped” & eliminated.

27
Q

Can pH trapping be used therapeutically?

A

Yes, for example Aspirin overdoses can be treated with NaHCO3 via urine alkalization.

28
Q

What is the primary route of elimination for lipid-soluble drugs and metabolites?

A

Bile/Feces

29
Q

What are examples of drugs that are eliminated through the bile/feces?

A

Digoxin, Steroids, & many hydrophobic agents.

30
Q

What can biliary/fecal excretion be affected by?

A

Intestinal & biliary disease such as Cholestasis (reduces bile flow and toxicity can result)
Enterohepatic recirculation or recycling
Transporter protein(OATPs, BCRP, PGPs, MDR/MRP) are involved in secretion of drugs & metabolites.

31
Q

What is enterohepatic recycling?

A

95% of the bile salts are reabsorbed into intestinal capillaries and returned to the liver by the hepatic portal vein. Bile salts via enterohepatic circulation stimulate hepatocytes to secrete more bile salts.

32
Q

What type of drugs is enterohepatic recycling going to affect?

A

Drugs excreted via bile into intestines for elimination.

Reabsorption occurs prior to excretion (therefore it is recycled)

33
Q

What are examples of drugs that go through enterohepatic recycling?

A

Ezetimibe, Isotretinoin, Atovaquone

34
Q

What does Zetia have such a long duration of action?

A

Because it goes through repeated recycling, Enterohepatic recycling.

35
Q

Will conjugated rugs be reabsorbed from the GI in Enterohepatic recycling?

A

No.

36
Q

How can enterohepatic recycling be clinically disruptive?

A

When the oral administration of activated charcoal or anion exchange resins and thereby trap drugs in the GI.

37
Q

What is the primary route of elimination for inhaled anesthetic agents?

A

Lungs/Exhalation

38
Q

How much of Isoflurane, Sevoflurane, and Halthane is eliminated unchanged through exhalation?

A

Isoflurane - 99%
Sevoflurane - 95%
Halothane - 70%
They all have Fluorine attached.

39
Q

What transporter actively transports drugs into breast milk?

A

BCRP

40
Q

What are examples of drugs that are transported into breast milk?

A

Topotecan (Hycamtin; anticancer drug)

Cimetidine (Tagamet; PPI)

41
Q

What drugs are of concern when it comes to elimination through tears?

A

Rifampin - causes orange-red coloration in some body fluids, including tears
Azo-based compounds - (Phenazopyridine) may cause similar effects
These may cause permanent staining of contact lenses.

42
Q

What are some PGP drug substrates?

A

Digoxin, HIV protease inhibitors (e.g. indinavir), Immunosupressive agnets (e.g. tacrolimus), Opioids (e.g. morphine sulfate), Loperamide

43
Q

“Normal” dosing takes PGP-mediated effects into account. T/F

A

True

44
Q

What are some PGP drug inhibitors?

A
Cyclosporine A
Quinidine
Ca channel blockers (Verapamil, Diltiazem, etc.)
Azole antifungals (Itraconazole)
Macrolide antibiotics (clarithromycin)
45
Q

What occurs when Loperimide and Quinidine are coadminsitered?

A

Quinidine blocks PGP-mediated efflux from CNS which leads to higher Loperamide levels in the CNS. This results in opioid toxicity and respiratory depression.

46
Q

What occurs when Quinidine & Digoxin are coadminsitered?

A

Quinidine blocks PGP-mediated renal elimination of digoxin, causing higher systemic levels of digoxin. This results in digoxin toxicity - arrhythmias.

47
Q

What occurs when Probenecid is coadminsitered with Penicillin G?

A

Probenecid inhibits OAT proteins which causes a decrease in the elimination of Penicilling G (This can be therapeutically useful).

48
Q

What occurs when Probenecid is coadminsitered with Methotrexate?

A

Probenecid inhibits OAT proteins which causes a decrease in the elimination of methotrexate (toxicity)

49
Q

What occurs when Rifampin and Talinolol are coadministrated?

A

Talinolol elimination increases by 30%

50
Q

What occurs when Rifampin and Cyclosporin A are coadministrated?

A

Cyclosporin bioavailability decreases from 27% to 10%.