Tetracyclines

Question 1

Chemically ?

Answer 1

Are derivatives of the polycyclic nucleus .Naphthacene carboxamide

Question 2

What is the sourses ?

Answer 2

They are obtained from cultures of streptomyces aureofaciens and streptomyces rimosus .

Question 3

Mention the 6 types ?

Answer 3

1- chlortetracycline
2- Oxytetracycline 
3- Tetracycline 
4- Demeclocycline 
5- Doxycycline 
6-Minocycline

Question 4

Mention the 2 semi-synthestic ?

Answer 4

Tetracycline

Doxycycline

Question 5

Mechanism of action ?

Answer 5

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

Question 6

Broad ?

Answer 6

Have abroad spectrum . they are effective against aerobic and anaerobic Gram positive and Gram negative bacteria

Question 7

Sensitive microorganisms include ?

Answer 7

• 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

Question 8

Why use of Tetracycline declines ?

Answer 8

Due to development of resistance by many strains , and appearance of supperior antibiotics , ues of Tetracyclines declines but still is used

Question 9

Therapeutic uses ?

Answer 9

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

Question 10

Routes of adminstration ?

Answer 10

Tetracycline are available in a wide variety of pharmaceutical forms for oral, parentral and Topical application

Question 11

Pharmacokinetics ? Absorption ?

Answer 11

Is incomplete from GIT ( about 30% in chlortetracycline, 60-80% in tetracycline ) But absorption of Doxycycline and Minocycline is almost complete

Question 12

Impaired of absorption ?

Answer 12

Absorption is impaired by Divalent ions like Ca++ , Mg++ if concurrently administered due to chelation

Question 13

is it teratogenic ?

Answer 13

Yes ,so we avoid give it to pregnant and lactation p

Caus deformed teeth , bone

Question 14

Distribution ?

Answer 14

Distribution of tetracycline through the body is wide ( water soluble ) -OH

Question 15

Metabolism ?

Answer 15

Hepatic metabolism occurs but is significant only in case of Minocycline

Question 16

Excretion ?

Answer 16

Mainly urinary although minor biliary excretion is taking place

Question 17

Adverse reactions ?

Answer 17

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 )

Question 18

Doses of chlortetracycline, oxytetracycline and tetracycline?

Answer 18

250- 500 mg 6 hourly for at least 4 days

Question 19

Doxycycline dose ?

Answer 19

200 mg then 100-200mg daily for at least 5 days

Question 20

Minocycline dose ?

Answer 20

250-500 mg 6 hourly for at least 4 days