• For some organic bases-tissue concentrations » plasma concentrations.
• True for: erythromycin, clindamycin, trimethoprim, and metronidazole.
• Extreme for: azithromycin, clarithromycin, tilmicosin, tulathromycin

Absorption

• For chloramphenicol: oral is usually good; im or sc is usually good through there is some controversy between dose forms.

For Macrolides and lincosamides:oral is usually good; im or sc is usually good