8 Drug Excretion

Drug Excretion

Irreversible removal of drug in the body

• polar,

• charged,

• hydrophilic,

• lipophobic,

• ionized

Requirements for excretion

• Renal Excretion

• Biliary Excretion

2 major processes for Drug Excretion

Renal Excretion

important in all drug excretions

Nephron

Functional unit of drug excretions

• Glomerular Filtration

• Tubular Secretion

• Tubular Reabsorption

3 Types of Renal Excretions

Glomerular Filtration

• Passive process

• Filtered: small, free drug (MW: <300)

• Either ionized or unionized

• NON-saturable

• Estimated considering the creatinine clearance (volume/min)

Tubular Secretion

• Req: Large and Bound

• Active process

• Has active transport system

• Organic anions (deprotonated forms of weak acids)

• Organic cations (protonated forms of weak bases)

Two energy requiring Tubular secretion

Tubular Reabsorption

• can be Passive (important) or Active Process

• Only unionized forms are absorbed

Iron Trapping

A process to increase the excretion:

basic drug (Sodium Bicarbonate)

Acidic drug toxicity → give __

acidic drug (Vitamin C& NH4Cl)

Basic drug toxicity → give __

Warfarin

Example of a drug that is highly protein bind

Biliary Excretion Rate

Favors compounds w/: MW: >300 & both polar, lipophilic groups

Enterohepatic Cycling

drugs excreted in the bile will be deconjugated in the intestine by bacterial flora, liberating the free that can be reabsorb back if it is lipid soluble

• Morphine &

• Digoxin

drugs that undergo enterohepatic cycling:

• Pulmonary Excretion

• Salivary Excretion

• Skin Excretion

• Mammary Excretion

4 minor routes of drug excretion

Pulmonary Excretion

this excretes Volatile substances & gases (NO & ethanol)

• Unionized, lipid-soluble → excreted through passive diffusion

• Ionized, hydrophilic → must be small sized

Requirements for Salivary excretion:

• caffeine,

• theophylline

examples of an unionized, lipid-soluble that is excreted through saliva

• urea,

• glycerol

examples of an Ionized, hydrophilic that is excreted through saliva

• Urticaria,

• Dermatitis

Drug excretion through skin may cause:

• Heavy metals

• Ethanol

Examples of skin excretion

weak base

Which will concentrate more in breast tissue?

weak base or weak acid

• Morphine,

• Codeine,

• Ethanol,

• Nicotine

Examples of drugs that are excreted through mammary

↑ kidney failure

↓ GFR =

↑ excretion

↑ GFR = _ excretion

↑ excretion

↑ secretion rate = _ excretion

↓ excretion

↑ reabsorption rate = _ excretion

↓ excretion

↑ protein binding = _ excretion

↑ B/G solubility

___B/G solubility – slow excretion (ethanol)

↓ B/G solubility

___B/G solubility – fast excretion (nitrous oxide)

C. Ion trapping

What term describes the alteration of urinary pH to inhibit reabsorption of toxins across the renal tubular membranes

A. Enterohepatic cycling

b. drug permeation

C. Ion trapping

D. renal reabsorption

D. Enterohepatic cycling

The rate of excretion is calculated by the following, except:

A. tubular secretion

B. tubular reabsorption

C. Glomerular filtration

D. Enterohepatic cycling

C. Distribution

Elimination refers to the following processes, except:

A. Metabolism

B. Excretion

C. Distribution

D. NOTA

A. unionized drug

Which of the following drug forms are reabsorbed in the renal tubules?

A. unionized drug

B. ionized drug

C. polar drug

D. AOTA

D. AOTA

What will happen if a basic drug is given to a nursing mother?

A. the drug will diffuse to the breast tissue

B. the drug becomes ionized in the breast tissue

C. the drug will be trapped in the breast tissue

D. AOTA

Passive

Passive or Active?

Glomerular Filtration

Active

Passive or Active?

Tubular Secretion

Passive and Active

Passive or Active?

Tubular Reabsorption

Active

Passive or Active?

biliary excretion