Benzylpenicillin of penicillin allergy. Use during pregnancy is generally safe. It is in the penicillin and β-lactam class of medications. Benzylpenicillin was discovered in 1929 by Alexander Fleming and came into commercial use in 1942. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. The wholesale cost in the developing world is about US$0.24–2.72 per day. In the United States a course of treatment costs $100–200. As an antibiotic, benzylpenicillin is noted to possess effectiveness mainly against Gram-positive organisms. Some Gram-negative organisms such as "Neisseria gonorrhoeae" and "Leptospira
History of penicillin (now Sandoz) developed the first acid-stable penicillin for oral administration, Penicillin V. American chemist John C. Sheehan of the Massachusetts Institute of Technology (MIT) subsequently completed the first chemical synthesis of penicillin in 1957. The second-generation semi-synthetic β-lactam antibiotic methicillin, designed to counter first-generation-resistant penicillinases, was introduced in the United Kingdom in 1959. Methicillin-resistant forms of "Staphylococcus aureus" likely already existed at the time. History of penicillin The history of penicillin follows a number of observations and discoveries of apparent evidence of antibiotic activity in molds before the modern isolation of the chemical penicillin in 1928. There are anecdotes about