Which semisynthetic penicillin was introduced to clinical use in 1961?

Ampicillin was the semisynthetic penicillin introduced to clinical use in 1961.

It was developed at Beecham Research Laboratories after researchers isolated 6-aminopenicillanic acid, or 6-APA, the core structure of penicillin. Chemists could attach different side chains to this nucleus, creating drugs with useful properties beyond those of the original penicillin.

Ampicillin was especially important because it could be taken orally and was active against some Gram-negative bacteria as well as Gram-positive bacteria. This gave it a broader range than benzylpenicillin, which was mainly effective against Gram-positive organisms. Ampicillin is an aminopenicillin and can be administered by mouth, injection, or intravenously.

A common mix-up is amoxicillin, another popular semisynthetic aminopenicillin. Amoxicillin was developed later and came into use in the early 1970s, while methicillin belongs to an earlier group of penicillins designed primarily to resist bacterial penicillinase enzymes.