Give some examples of drugs that are poorly absorbed and explain why these drugs are poorly absorbed.
1. Penicillin G, insulin, and other peptides: destroyed by stomach acid or digestive enzymes.
2. Tetracyclines: chelated to components of food to form insoluble complexes.
3. Aminoglycoside antibiotics (streptomycin, gentamycin: so polar they won't cross cell membranes.
4. Nitroglycerin, adrenaline, dopamine: undergo extensive metabolism.