Penicillins consist of a thiazolidine ring (A) connected to a b-lactam ring (B), to which is attached a side chain (R) (Figure 44—1). The penicillin nucleus itself is the chief structural requirement for biological activity. The discovery that 6-aminopenicillanic acid could be obtained from cultures that were depleted of side-chain precursors led to the development of the semisynthetic penicillins, which have side chains that alter the susceptibility of the resulting compounds to inactivating enzymes (b-lactamases) and that change the antibacterial activity and pharmacological properties of the drug (Table 44—1).

The international unit of penicillin is the specific penicillin activity contained in 0.6 mg of the crystalline sodium salt of penicillin G. Doses of semisynthetic penicillins are expressed by weight.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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