TABLE 1.

Pharmacodynamic and pharmacokinetic overview of select antibiotics and their effect on the microbiota^{28–30,32,33,35,37}

	Ampicillin	Clindamycin	Metronidazole	Neomycin	Vancomycin
Classification	Aminopenicillin	Lincosamide	Nitroimidazole	Aminoglycoside	Glycopeptide
Route of administration	Intramuscular   Intravenous   Oral	Intramuscular   Intravenous   Oral   Topical   Vaginal	Intravenous   Oral   Topical   Vaginal	Intravenous   Intramuscular   Oral   Topical	Intraocular   Intraperitoneal   Intrathecal   Intravenous   Intraventricular Oral
Spectrum	(1) Gram + (2) Gram – (3) Anaerobes	(1) Gram + (2) Anaerobes	(1) Anaerobes	(1) Gram – (2) Aerobes	(1) Gram + (2) Aerobes
Intestinal absorption by oral administration	Moderate absorption	High absorption	High absorption	Minimal absorption	Minimal absorption
Site of absorption	Small Intestine	Small Intestine	Small Intestine	—	—
Clearance mechanism	Renala	Biliary	Renala Biliary	Renal	Renala Minimal Biliary
Microbiota diversity with oral administration	Long-term changes	Long-term changes	Short-term changes	Long-term changes	Long-term changes
Microbiota diversity with systemic administration	Long-term changes	Long-term changes	Undetermined	Minimal changes	Minimal changes

The pharmacological properties of select antibiotics and their effect on the microbiota are shown. Possible routes of administration—not just the methods commonly used in the clinical setting—are described. Various bacterial exceptions are excluded from spectrum; and moderate absorption and high absorption are defined as 40%-60% and 61%-100%, respectively. Antibiotics may be excreted unchanged in the urine, bile, and/or feces. These antibiotics, depending upon route of administration, may also affect the diversity of species in the intestinal microbiota. These changes may be short-term (less than 2 weeks) or long-term (greater than 2 weeks).

^aPrimary excretion mechanism.