The tetracyclines, including
doxycycline and minocycline, are bacteriostatic unless given in high doses. If high blood levels are
not attained, treatment failures in early and late disease are common. However, these high doses can be difficult to tolerate. For example, doxycycline can be very effective but only if adequate blood levels are achieved either by high oral doses (300 to 600 mg daily) or by parenteral (IV) administration.