penicillin G

noun

-ˈjē 

: the penicillin C₁₆H₁₈N₂O₄S that constitutes the principal or sole component of most commercial preparations and is used chiefly in the form of its stable salts (as the sodium salt C₁₆H₁₇N₂NaO₄S or potassium salt C₁₆H₁₇KN₂O₄S)

called also benzylpenicillin

see penicillin g benzathine, penicillin g procaine