Tetracyclines

Tetracyclines are broad-spectrum bacteriostatic antibiotika. It used to be widely used in pediatrics, but only until it was found to damage tooth enamel and growth cartilage.

Antimicrobial spectrum

 * Broad spectrum, G + and G−, mycoplasmas, chlamydia , spirochetes , some protozoa (amoebae).
 * Many strains are resistant (many G + cocci, G− aerobic rods), resistance is cross-linked.
 * Does not affect Pseudomonas spp., Proteus spp. and Serratia spp.

Mechanism of action

 * Inhibition of proteosynthesis, reversible binding to the 30S subunit of the ribosome.

Pharmacokinetics

 * It is preferred after administration, better on an empty stomach.
 * They form inactive chelates with Ca 2+, Fe 2+ , Mg 2+ , Al 3+ ions , which limit absorption - do not administer simultaneously with antacids , do not drink with milk.
 * Tissue penetration very good.
 * They penetrate the placenta, high risk of fetal damage.
 * They are widely distributed - in addition to the CNS, they penetrate mainly into bones and teeth, into milk (they cannot be given during pregnancy and lactation).
 * They are concentrated in the liver, subject to enterohepatic circulation, excreted in the bile , and doxycycline is excreted in the faeces, otherwise by the kidneys.

Pharmacodynamics

 * Bacteriostaticity does not depend on concentration but on exposure time.
 * Their postantibiotic effect is insignificant.

Side effects

 * There are many side effects, which affects the possibility of their use.
 * Bone deposition and interference with tooth enamel, tooth enamel damage, tooth discoloration , phototoxicity, GIT problems ( nausea , vomiting , diarrhea ), suppression of the natural flora in the GIT (may result in blood clotting disorders due to vitamin K deficiency , superinfection), fatty liver degeneration.

Contraindication

 * Pregnant and lactating women, children up to 8 years.

Hlavní indikace

 * Chlamydiové infekce, infekce ehrlichiemi, rickettsiemi, brucelami, mykoplasmaty.
 * Infekce ve stomatologii.
 * Bakteriální postižení žlučových, močových a pohlavních cest.
 * Některé antropozoonózy.
 * Acne vulgaris.

Interakce

 * Nekombinovat s betalaktamy.
 * Zvyšuje účinek PAD, imunosupresiv a digoxinu.

Zástupci
1. generace: tetracyklin, oxytetracyklin, rolitetracyklin pro i.m. či i.v. podání.

2. generace: doxycyklin a minocyklin.

3. generace: thiacyklin – nemá zkříženou resistenci.

Dnes se v praxi používají pouze doxycyklin a minocyklin.

Doxycyklin

 * Velmi lipofilní.
 * Podává se p.o. i parenterálně, jeho absorpce je ovlivněna méně než u ostatních tetracyklinů.
 * Má dlouhý poločas (16 hodin) – dávkování à 12 či 24 hodin.
 * Dávkování – první den 2 × 100 mg, další dny 100 mg à 24 hodin.

Minocyklin

 * Specifická indikace – akné.