16
③ Minor structure changes in existing agents
Penicillin,青霉素
Ampicillin,氨苄西林
Penicillin ∨
Oxacillin,苯唑西林
17
Disadvantages of penicillin: unstable to acid unstable to β-lactamase(内酰胺酶) little effect on Gram negative bacteria(革 兰氏阴性菌)
18
④ Programmed basic research with synthesis of specific chemicals e.g.1 Histamie(H2) receptor antagonist (such as Cimetidine西米替丁) for peptic ulcer Histamine receptors can be classified in to three classes , H1,H2 and H3, they distribute in different tissues, and cause different effects when agitated. H2 receptor exists in gastric wall cells, when agitated by histamine the secretion of gastric acid is enhanced , causing peptic ulcer . H2 receptor antagonist can specifically bind with H2 receptor but without agitation.