This document discusses tetracycline antibiotics. It notes that tetracyclines suppress a wide range of gram-positive and gram-negative bacteria, as well as other microorganisms. They work by inhibiting protein synthesis by binding to the 30S subunit of bacterial ribosomes. Common side effects include gastrointestinal irritation. Tetracyclines are generally not recommended as first-line treatment but may be used for selected infections like rickettsial diseases. Newer tetracycline derivatives like doxycycline and minocycline have improved properties like better absorption and tissue penetration.

15. DR.V. SATHYANARAYANAN. M.D.
PROFESSOR OF PHARMACOLOGY

16. • Suppresses
• Gram +ve bacteria
• Gram negative bacteria
• Rickettsia
• Chlamydia
• Mycoplasma
• Some protozoa

19. • Antimicrobial agents with 4 cyclic rings
• Obtained from the soil actinomycetes
• Bacteriostatic

27.  inhibit protein synthesis by binding to 30 S
subunit of ribosomes

29. • Taken up by the organisms
• By active transport
• Binds to “ A ” site of 30 S subunit of ribosomes
• Prevent binding of tRNA to this site
• Thereby prevent transfer of amino acids for
protein synthesis
• Inhibition of protein synthesis
• Failure of growth and multiplication

33. • SHORT ACTING ( t1/2 – 6 hrs )
 chlortetracycline
 tetracycline
 oxytetracycline
• INTERMEDIATE ACTING ( t1/2 – 12 hrs )
 Demeclocycline
 methacycline
• LONG ACTING ( t1/2 – 18 hrs )
 Doxycycline
 Minocycline


34. • Suppresses
• Gram +ve bacteria
• Gram negative bacteria
• Rickettsia
• Chlamydia
• Mycoplasma
• actinomycetes
• Some protozoa

36.  :All G+ve, G-ve cocci (staphylococci, streptococci,
gonococci, meningococci )
 most G+ve Bacilli – Clostridia, listeria, corynebacteria
,bacillus anthracis,
 G-ve bacilli – H.ducreyi , v.cholerae , brucella
Pneumonia, yersinia pestis, campylobacter, bordetella,
pasturella, spirochetes
• Rickettsia
• Chlamydia
• Mycoplasma
• Some protozoa - E.Histolytica ,plasmodium
 Enterobacter , pseudomonas, proteus, klebsiella ,
salmonella (not inhibited )
 Actinomycetes , (inhibit at high cone )

39.  Many organisms developed
 Plasmid mediated
 Decreased uptake
 Efflux
 Displacement
 Inactivation
 Cross resistance also

43. • Food interferes with absorption
• Chelating property with calcium
• milk ,iron,antacids, zinc → ↓absorption
• Undergo enterohepatic circulation
• Widely distributed
• Attain good concentration in all secretions including
CSF
• CROSS PLACENTA
• primary excreted in urine  dose ↓in renal failure
(not doxycycline )

48. • oral capsules 250 – 500 mg QID
• ½ hr before or 2 hr after food
• I.M route to be avoided
• doxycycline ,minocycline can be given
i.v

53.  GASTROINTESTINAL IRRITATION → Epigastric pain ,
vomiting ,diarrhea
 HEPATOTOXICITY (oxy,tetra )
 RENAL TOXICITY ( except Doxy ) – aggravates renal failure
due to increased levels nitrogen from anti anabolic action
 REVERSIBLE FANCONY LIKE SYNDROME → due to out dated
tetracycline
 Vomiting, proteinuria, polyuria, glycosuria, acidosis

61. • Photo toxicity  ( sun burn like skin reactions,
dermatitis ) Demeclocycline, Doxycycline more likely
• Effect on teeth and bones deposits in the
developing  cause deformities
• Brownish discoloration, pigmentation of teeth
• Depressed bone growth
• Onycholysis, pigmentation of nails
• TERATOGENIC

71. • SUPERINFECTION : most common with TCs 
due to suppression of normal bacterial flora of
intestine
• HYPERSENSITIVITY REACTION →not very
common
• ANTIANABLIC EFFECT : large doses for longer
periods 
• negative nitrogen balance →
• ↑blood urea ↑ ICT

80.  PSEUDOTUMOR CEREBRI due to ↑ ICT
 NEPHROGENIC DIABETES INSIPIDUS 
inhibition of ADH action in kidneys by demeclocycline
 LONGTERM 
• leukocytosis,
• thrombocytopenic purpura


84. • pregnancy, lactation, children upto 8 years
• Renal and hepatic insufficiency
• Beyond their expiry date
• mixing with other drugs during injections
• Intrathecal, intramuscular route

89.  EARLIER  Was preferred for empirical
therapy for most infections
 NOW ONLY FOR SELECTED INFECTIONS
 Several organisms lost sensitivity
 Several alternatives are available

94.  TETRACYCLINES ARE DRUGS OF CHOICE IN
 RICKETTSIAL INFECTIONS :
 Tick typhus
 Q fever
 Rocky mountain spotted fever
 2g 6 hourly followed by 1g 6 hourly

99. CHLAMYDIAL INFECTIONS :
 Lymphogranuloma venereum  TC for 2
weeks
 Trachoma  topical, oral TCs upto 40 days
 Inclusion conjunctivitis
 Urethritis / cervicitis
 Chlamydia pneumoniae
 psittacosis

109. 
 ATYPICAL PNEUMONIA due to Mycoplasma pneumoniae
 GRANULOMA INGUINALE due to calymmatobacterium
granulomatis
 CHOLERA –single dose of 200mg of doxycycline
reduces duration of illness ( adjuvant value )
treatment of dehydration is lifesaving
 BRUCELLOSIS
 PLAGUE

124.  TRAVELLER”S DIARRHOEA
 OTHER STDs like gonorrhea, syphilis , chancroid
 TULARAEMIA
 LYME DISEASE
 RELAPSING FEVER
 LEPTOSPIROSIS
 Post exposure prophylaxis of ANTHRAX
 EYE INFECTIONS - TOPICALLY

128.  SOME PROTOZOAL INFECTIONS LIKE :
 CHRONIC INTESTINAL AMOEBIASIS
 MULTI-DRUG RESISTANT MALARIA
 Miscellaneous
 H.pylori infction
 ACNE 250 mg BD for 4 weeks
 INAPPROPRIATE SECRETION OF ADH

135.  Incomplete oral absorption
 75% bioavailability
 Low lipid solubility
 QID dose
 Not safe in renal impairment
 High incidence of superinfection

137.  Semisynthetic
 High potency
 Complete intestinal absorption ( food does not
interfere )
 95% bioavailability
 primarily excreted through gut  safe in renal
impairment
 t ½ - 18-24 hrs
 Less superinfection
 High phototoxicity
 Dose : 200 mg initially, then 100 mg OD for 6-14 days

146.  Semisynthetic
 100% absorbed
 Highly lipid soluble
 Long t1/2  OD dose
 Cause vestibular toxicity  vertigo,
dizziness, ataxia, nausea, vomiting
 Alternative to rifampicin for meningococcal
carriers

153.  SYNTHETIC BROAD SPECTRUM AMA
 MECHANISM OF ACTION :
 Binds with 50 s ribosomal subunit  inhibits
transpeptidation reaction - inhibit protein synthesis
 BACTERIOSTATIC
 Resistance seen

154.  similar to Tetracyclines
 (G+ve, G –ve ,rickettsiae ,chlamediae,
mycoplasma )
 salmonella ,shigella, h. influenza ,
klebsiella….. etc
BACTERICIDAL to
 Neisseria meningitidis,
 H. influenzae
 bacteroides (anerobes)

155.  rapidly & completely absorbed from the
intestine
 EXCELLENT TISSUE PENETRATION
 ATTAINS HIGH CONCENTRATION IN CSF
 Crosses placenta
 Metabolized in liver & excreted in urine

159.  Chloramphenicol Capsules orally 250-
500mg QID
 Chloramphenicol Eye /Ear drops
 Chloramphenicol Palmitate , succinate
– 1g vial i.v, i.m

163.  GI SYMPTOMS  nausea, vomiting, diarrhoea
 BONE MARROW DEPRESSION  anemia, leukopenia,
thrombocytopenia
 Dose dependent -
 Idiosyncratic response – 1 in 30,000 people, genetic,
fatal
 GRAY BABY SYNDROME New born babies given high
dose, fatal, gray cyanosis(inadequate liver, kidney
function)
 HYPERSENSITIVITY REACTIONS  rash, fever 
uncommon
 SUPERINFECTION  can occur

166.  INHIBITS HEPATIC MICROSOMAL ENZYMES
 INCREASES BLOOD LEVELS OF
 Phenytoin
 tolbutamide
 warfarin
 INCREASED TOXICITY

167.  TYPHOID FEVER – sensitive strains – alternative to
other drugs
500 mg QID till fever subsides, then 250 mg QID till
14th day
 BACTERIAL MENINGITIS – due to H.influenza &
meningococci ( alternative to penicillin &
cepahalosporins )
 ANAEROBIC INFECTIONS – only in severe cases
 RICKETTSIAL INFECTIONS – alternative to
tetracycline
 EYE AND EAR INFECTIONS - topically

178.  Derivative of minocycline
 Broad antibacterial spectrum
 MRSA, VRSA, VRE, MDRE
 Anaerobes
 Effective against Resistant organisms to tetracyclines
 Given I.V = 100mg initially, followed by 50 mg BID
 Safe in renal impairment
 Well tolerated
 Used in life threatening infections due to resistant
organisms
 Hospital acquired infections
 Intra-abdominal infections