infectious diseases
Tetracyclines
Pharmacokinetics
About 60 to 80% oftetracyclineand≥90% ofdoxycyclineandminocyclineare absorbed after oral use. However, absorption is decreased by metallic cations (eg, aluminum, calcium, magnesium, iron); thus, tetracyclines cannot be taken with preparations containing these substances (eg, antacids, many vitamin and mineral supplements).Tetracyclineandomadacyclineshould be taken with plenty of water on an empty stomach. Food decreases absorption of other tetracyclines as well, but this effect is less significant fordoxycyclineandminocycline. Tetracyclines penetrate into most body tissues and fluids. All are concentrated in unobstructed bile. However, cerebrospinal fluid levels are not reliably therapeutic.Minocyclineis the onlytetracyclinethat reaches high concentrations in tears and saliva. Tetracyclineandminocyclineare excreted primarily in urine.Doxycycline,eravacycline, andomadacyclineare excreted primarily in the intestinal tract. 