Abdul Waheed

M pharm-Pharmacology

Department of pharmacology

Amity University, Noida1

INTRODUCTION• Obtained from soil actinimycetes.

• Introduced in 1948 by Benjamin Minge Duggar(chlortetracycline, aureomycin).

• Tetracyclines is broad spectrum antibiotic having four cyclic ring nucleus.

• All tetracyclines are slightly bitter solids, weakly water soluble, their hydrochlorides are more soluble.

• Aqueous solutions are unstable.2

• Tetracyclines available in India for clinical

use:- Tetracycline, Oxytetracycline,

Demeclocycline, Doxycycline, Minocycline.

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MECHANISM OF ACTION

• Tetracyclines are primarily bacteriostatic.

• Inhibit protein synthesis by binding to 30s

ribosome in susceptable organism.

• Inhibit binding of aminoacyl tRNA to the

acceptor site of mRNA peptide chain fails to

grow.

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TRANSPORT OF

TETRACYCLINES

• Sensitive organism have active transport process

which concentrate tetracyclines intracellularly.

• In gram negative bacteria tetracyclines diffuse

through “Porin” channel.

• Some lipid soluble member (Doxycycline and

Minocycline) enter by passive diffusion.

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ANTIMICROBIAL SPECTRUM

• Inhibit all type of pathogen except Fungi and Viruses.

• Cocci: All gram positive and gram negative cocci were

originally sensitive but Strep. pyogenes, Staph. aureus and

enterococci have become resistant.

• Sensitive gram positive bacilli: Clostridia and other anaerobes,

Listeria, Corynebacteria, B. anthracis are inhibited but not

Mycobacteria.

• Sensitive gram nagetive bacilli: H. ducreyi, H. pylori, Yersinia

pestis, Y. enterocolitica, and many anaerobes. H.influenzae

have become insensitive.

• All rickettsiae and chlamydiae are highly sensitive.

• Mycoplasma & Actinomyces are moderately sensitive.

• E. histolytica & Plasmodia are inhibited at high concentration

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RESISTANCE

• Tetracyclines concentrating mechanism become

less effective.

• Bacteria acquire capacity to pump tetracyclines

out.

• Plasmid mediated synthesis of a “Protection”

protein which protects the ribosomal binding site

from tetracyclines.

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PHARMACOKINETICS

• Incompletely absorbed by g.i.t.

• Absorption is better if taken in empty stomach.

• Doxycycline & Minocycline are completely absorbed

irrespective of food.

• Tetracyclines have chelating property with calcium

and other metals forms insoluble and unabsorbable

complexes.

• Milk, iron preparation, nonsystemic antacids and

sucralfate reduces their absorption.

• Concentrated in liver and spleen and bind to the

connective tissue in bone and teeth.

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Continue…

• Widely distributed in body

• Variable degree of protein binding: high

(Demeclocycline, Doxycycline, & Minocycline,)

moderate (tetracycline) low (Oxytetracycline)

• Primarily excreted in urine by glomerular

filtration.

• They are secreted in milk and affect the infant.

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ADMINISTRATION

• Most commonly used dosage form- Oral capsule.

• The capsule should be taken 1/2hr before or 2hr

after food .

• Tetracyclines are not recommended by i.m. route.

(painful & poor absorption).

• i.v. injection may be given in sever cases.

• Topical preparation are available but should not

be used because of high risk of sensitization.

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ADVERSE EFFECT

• Epigastric pain, nausea, vomiting and diarrhoea

by their irritant property.

• Liver damage and jaundice occurs occasionally.

• All Tetracyclines except Doxycycline accumulate

and enhance renal failure.

• Tetracyclines have chelating property and affect

the teeth and bones.

• Reduces protein synthesis and induces negative

nitrogen balances increase blood urea.11

PRECAUTION

• Should not be used during pregnancy, lactation

and in children.

• Should be avoided in patients on diuretics

increases blood urea.

• Do not mix injectable Tetracyclines with

Penicillin causes inactivation.

• Do not inject Tetracyclines intrathecally.

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USE

• Broad spectrum antibiotics

• Atypical pneumonia

• Cholera

• Brucellosis

• Plague

• Rickettsial infection

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PREPARATIONS

• TERRAMYCIN 250, 500 mg cap, 50 mg/ml in

10 ml vial inj.

• ACHROMYCIN, HOSTACYCLINE,

RESTECLIN 250, 500 mg cap.

• LEDERMYCIN 150, 300 mg cap/tab.

• TETRADOX, NOVADOX 100 mg cap.

• CYANOMYCIN 50, 100 mg cap.

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Reference

• Tripathi KD, Essentials of Medical Pharmacology, Jaypee Publishers, New Delhi.

• Sharma HL, Sharma KK, Principles of Pharmacology, Paras Medical Publishers, New Delhi

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