Tetracyclines Flashcards
Chemically ?
Are derivatives of the polycyclic nucleus .Naphthacene carboxamide
What is the sourses ?
They are obtained from cultures of streptomyces aureofaciens and streptomyces rimosus .
Mention the 6 types ?
1- chlortetracycline 2- Oxytetracycline 3- Tetracycline 4- Demeclocycline 5- Doxycycline 6-Minocycline
Mention the 2 semi-synthestic ?
Tetracycline
Doxycycline
Mechanism of action ?
Tetracycline act by inhibit bacterial protein biosythesis by binding to the 30S bacterial Ribosome and preventing access of aminoacyl tRNA to the acceptor (A) site on in RNA Ribosome complex
Broad ?
Have abroad spectrum . they are effective against aerobic and anaerobic Gram positive and Gram negative bacteria
Sensitive microorganisms include ?
- All Gram poaitive microorganisms (in general )
- Neisseria gonorrhea
- Neisseria meningitidis
- Haemophillus influenza
- Staphylococcus aureus
- streptoccus spp
- Pseudomonas pseudomallei
- Treponoma pallidum
- Vibrio cholera
- Brucella spp
- Propionibacterium
- Rickettsiae
- Spiochetes
- Chlamydia spp
- Mycoplasma spp
Why use of Tetracycline declines ?
Due to development of resistance by many strains , and appearance of supperior antibiotics , ues of Tetracyclines declines but still is used
Therapeutic uses ?
1- Diseases caused by Mycoplasmas 2- Diseases caused by chlamydia 3- Sexually transmitred Diseases 4- Brucellosis 5- Diseases caused by Shigella spp 6- Actinomycosis 7- Acene 8- Sensitive urinary tract infections
Routes of adminstration ?
Tetracycline are available in a wide variety of pharmaceutical forms for oral, parentral and Topical application
Pharmacokinetics ? Absorption ?
Is incomplete from GIT ( about 30% in chlortetracycline, 60-80% in tetracycline ) But absorption of Doxycycline and Minocycline is almost complete
Impaired of absorption ?
Absorption is impaired by Divalent ions like Ca++ , Mg++ if concurrently administered due to chelation
is it teratogenic ?
Yes ,so we avoid give it to pregnant and lactation p
Caus deformed teeth , bone
Distribution ?
Distribution of tetracycline through the body is wide ( water soluble ) -OH
Metabolism ?
Hepatic metabolism occurs but is significant only in case of Minocycline
Excretion ?
Mainly urinary although minor biliary excretion is taking place
Adverse reactions ?
1- Gastroinestinal effects :- irritation, nausea , vomitting , epigastric distress.
2- Hepatotoxicity :- hepatic damage , Jaundice , azotemia , acidosis ,irreversible shock .
3- Renal toxicity :- tetracycline may aggravate uremia in patients with renal diseases , azotemia is increased .
4- discoloration of enemal of teeth is caused in children receiving tetracycline or adults who use them for long time
5- photosensitivity
6- hypersensitivitry reactions ( urtiticaria , skin rash , eruptions )
Doses of chlortetracycline, oxytetracycline and tetracycline?
250- 500 mg 6 hourly for at least 4 days
Doxycycline dose ?
200 mg then 100-200mg daily for at least 5 days
Minocycline dose ?
250-500 mg 6 hourly for at least 4 days