Penicillins

The penicillins are a group of broad-spectrum, bactericidal antibiotics. They are known as beta-lactam drugs for the four-membered lactam ring they have in common. The penicillins also share many features with the cephalosporins, and beta-lactamase inhibitors (clavulanic acid being one).

The penicillins are derived from a number of strains of Penicillin natatum and chrysogenus. These strains can be seen as mold on bread and fruit.

The penicillins, which include their semisynthetics, share common action. They inhibit the synthesis of bacterial cell walls and prevent linkage of structural components to the cell , as well. They are active against Gram-positive and a few Gram-negative organisms.

Penicillins are not completely absorbed when given orally due to gastric acidity and food, though the synthetic agents do achieve absorption better.
That which is absorbed is widely distributed in the body, but is limited in reaching effective levels in cerebral spinal fluid, and does so only when the meninges are inflamed. It is also absorbed across the placental barrier.

The Penicillins are excreted by the kidneys as well as in breast milk.