Tetracyclines, introduced in 1948, are broad-spectrum antibiotics effective against a variety of pathogens but not fungi or viruses. They work by inhibiting protein synthesis in bacteria and are primarily excreted in urine, with absorption affected by food and certain metals. Tetracyclines have several side effects, contraindications during pregnancy and lactation, and are used in treating infections like pneumonia and cholera.

1. Abdul Waheed
M pharm-Pharmacology
Department of pharmacology
Amity University, Noida
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2. 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.
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3. • Tetracyclines available in India for clinical
use:- Tetracycline, Oxytetracycline,
Demeclocycline, Doxycycline, Minocycline.
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4. 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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5. 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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6. 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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7. 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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8. 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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9. 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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10. 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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11. 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.
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12. 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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13. USE
• Broad spectrum antibiotics
• Atypical pneumonia
• Cholera
• Brucellosis
• Plague
• Rickettsial infection
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14. 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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15. 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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