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.

Main indications

• Chlamydial infections , ehrlichemia infections , rickettsiae , brucellosis infections , mycoplasmas .
• Infections in dentistry.
• Bacterial involvement of the bile, urinary and genital tracts .
• Some anthropozoonoses .
• Acne vulgaris .

Interaction

• Do not combine with beta-lactams .
• Increases the effect of PAD , immunosuppressants and digoxin .

Representatives

1st generation : tetracycline, oxytetracycline, rolitetracycline for im or iv administration.

2nd generation : doxycycline and minocycline.

3rd generation : thiacycline - does not have cross-resistance.

Today, only doxycycline and minocycline are used in practice.

Doxycycline

• Very lipophilic.
• It is administered parenterally, its absorption is less affected than with other tetracyclines.
• It has a long half-life (16 hours) - dosing of 12 or 24 hours.
• Dosage - first day 2 × 100 mg , next days 100 mg every 24 hours.

Minocycline

• Specific indication - acne.

Links

Source

BENEŠ, Jiří. Studijní materiály [online]. [cit. 2010]. <http://jirben.wz.cz>.

References

• LINCOVÁ, Dagmar a Hassan FARGHALI, et al. Základní a aplikovaná farmakologie. 2. vydání. Praha : Galén, 2007. s. 481-483. ISBN 978-80-7262-373-0.

• HAVLÍK, Jiří, et al. Infektologie. 2. vydání. Praha : Avicenum, 1990. 393 s. ISBN 80-201-0062-8.

• LOBOVSKÁ, Alena. Infekční nemoci. 1. vydání. Praha : Karolinum, 2001. 263 s. ISBN 80-246-0116-8.

• MARTÍNKOVÁ, Jiřina, Stanislav MIČUDA a Jolana CERMANOVÁ, et al. Vybrané kapitoly z klinické farmakologie pro bakalářské studium [online]. ©2005. [cit. 2010-08-14]. <https://www.lfhk.cuni.cz/farmakol/predn/prednbak.htm/>.