Antimicrobial agents/drugs synthetic

Strictly, the definition should refer to substances that are antagonistic in dilute solution because it is necessary to exclude various common metabolic products such as alcohols and hydrogen peroxide. The term antibiotic is now commonly used for antimicrobial drugs in general, and it would be pedantic to object to this. Today, many commonly-used antibiotics are either fully synthetic or are produced by major chemical modification of naturally produced molecules hence, antimicrobial agent is perhaps a more accurate term, but antibiotic is much the commoner usage. 

Synthetic drug An antimicrobial agent synthesized chemically in the laboratory. 

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