Overview Cell membranes bilayer of amphipathic lipids with the hydrophobic chains pointing inwards and the hydrophilic heads pointing outwards like dissolves like, thus charged (ionized) molecules will have a difficult time crossing this bilayer with uncharged (non-ionized) molecules crossing more easily Urine pH tends to be acidic but pH ranges from 4.6 - 8.0 Weak acids and bases Weak acids RCOOH (lipid soluble) ↔ RCOO- (trapped) + H+ in basic environments, weak acids become charged by deprotonation will become trapped on side of the lipid bilayer that is basic to treat overdose of weak acids, administer bicarbonate (weak base) examples of drugs that are weak acids aspirin phenobarbital methotrexate Weak bases RNH3+ (trapped) ↔ RNH2 (lipid soluble) + H+ in acidic environments, weak bases become charged by protonation will become trapped on the side of the lipid bilayer that is acidic to treat overdose of weak bases, administer ammonium chloride (weak acid) example of a drug that is a weak base amphetamines/methamphetamines TCAs TCA overdose treated with sodium bicarbonate