Page 174 - Interactive Theoritical Notes of Bioharmaceutics and pharamcokinetics.docx compressed

PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

5. Mammary excretion

• Milk consists of lactic secretions which is rich in fats and proteins.

• Free un-ionized and lipid soluble drugs diffuse passively.

• Both basic substances and lipid-soluble compounds can be excreted into milk.
o Basic substances can be concentrated in milk since milk is more acidic (pH ~ 6.5)

than blood plasma.

o Since milk contains 3-4% lipids, lipid-soluble drugs can diffuse along with fats

from plasma into the mammary gland and thus can be present in mother's milk.

o Substances that are chemically similar to calcium can also be excreted into milk

along with calcium.

 Highly plasma protein bound drugs like diazepam is less secreted in milk.

Adverse effects

 Discoloration of teeth with tetracycline.

 Jaundice due to interaction of bilirubin with sulfonamides.

 Nicotine is secreted in the milk of mothers who smoke.

6. Skin excretion

Drugs excreted through skin via sweat follows pH partition hypothesis.

Excretion of drugs through skin may lead to urticaria and dermatitis.
Compounds like benzoic, salicylic acid, alcohol and heavy metals like lead,

They are excreted in sweat.

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