Jun 13, 2005 An orally active naturally penicillin, phenoxymethylpenicillin is used to Phenoxymethylpenicillin is a narrow spectrum antibiotic also commonly referred to as Penicillin V or Penicillin VK. . Monoisotopic: 350.093642386; Chemical Formula: C16H18N2O5S .. Mass Spec (NIST): Not...