Tetracycline

Tetracyclines are known to have teratogenic effects. Consumption of Tetracycline during pregnancy may cause dental enamel dysplasia and bony deformities in the child.

Ref: KDT, 6th Edition, Page 714; Basic and Clinical Pharmacology By Katzung, 10th Edition, Page 748

Tetracyclines are bacteriostatic antibiotics.

It inhibits protein synthesis by binding to 30S ribosomal subunit, and prevents the attachment of aminoacyl tRNA to the mRNA – ribosome complex. As a result peptide chain fails to grow.

Ref: Essentials of Medical Pharmacology, 5th Edition, Page 668-73

Tetracycline is the drug of choice for chemoprophylaxis of cholera.

Ref: Preventive and Social Medicine, by K.Park, 19th edition, Page 106, 193, 194, 141, 142; Harrison’s Internal Medicine, 16th edition, Page 917, 991.

In rhinoscleromatosis, organism may be difficult to eradicate, despite aggressive therapy.

A combination of conservative surgical debridement and long-term antibiotic coverage is the mainstay of therapy for rhinoscleroma.

Tetracycline has been shown to be effective and inexpensive for patients unless contraindicated.

Fluoroquinolones may be used as an alternative, given their excellent gram-negative activity and convenient dosing regimen

Ans. is ‘a’ i.e., Tetracycline 

Ans. is ‘a’ i.e., Tetracycline

Ans. is ‘a’ i.e., Tetracycline labeling

Tetracycline labeling for osteoid mineralization

o Tetracycline labeling is the method of choice fir estimating newly systhesized osteoid mineralization in human. o Tetracycline is incorporated into new areas of osteoid that are being laid down but not yet mineralized (osteoid seams) o To estimate the rate of newly synthesized osteoid mineralization tetracycline is administered to the subject at two

defined time points.

o If the time interval between the two course is known , both the rate and extent of mineralization can be measured. o Tetracycline labelling allows a distinction to be made between defective mineralization (osteomalacia) and increased osteoid synthesis (bone remodeling states) by revealing the calcification front.

Other stain used for osteoid mineralization

o Other stain can also be used for this purpose, but they are inferior to tetracycline:

it) Alizarin red

ii) Calcein

Von-Kossa

Ans. is ‘a’ i.e., Tetracycline

Ans. is ‘b’ i.e., Binding to 30S Subunit and inhibits binding of aminoacyl tRNA

o Tetracycline interact with small ribosomal subunits, blocking access of aminoacyl- tRNA to the mRNA-ribosome complex.

o Tetracyclines bind to 30 S subunit of ribosome.

Ans. is ‘a’ i.e., Bind to A site and inhibit attachment of t-RNA

Ans. is ‘a’ i.e., It is not teratogenic

o Tetracycline is teratogenic – causes discoloration and defects of teeth and altered bone growth of the fetus.

o Tetracycline can cause superinfection (including pseudomembranous colitis).

Ans. is ‘c’ i.e., Radial

o As with all intramuscular preparations, terramycin (oxytetracycline) intramuscular solution should be injected well within the body of a relatively large muscle.

o In infants and small children the periphery of the upper outer quadrant of the gluteal region should be used only when necessary, such as in burn patients, in order to minimize the possibility of damage to the sciatic nerve.

o The deltoid area should be used only if well developed such as in certain adults and older children, and then only with caution to avoid radial nerve injury.

Ans. is ‘b’ i.e., Tetracycline

Drugs causing Pseudotumour cerebri

o A miodarone                                           o Mineralocorticoids (withdrawl)                o Oral contraceptives

o Glucocorticoids (withdrawl)                  o Hypervitaminosis A                                  o Tetracyclines

o Quinolones

C i.e. Labelled tetracycline

• Tetracycline administered in vivo becomes fixed in new forming mineralizing boneQ and exhibit a characteristic fluorescence when viewed by ultraviolet light.
• The tetracycline labelled bone fluoresces a bringt yellow (dimethyl chlortetracycline) to yellowish green (oxytetracyline) on faint magenta background and mature bone fluoresces a faint blue. Under fluorescent microscopy, narrow bands of fluorescence are observed where bone was actively formed while exposed to the recently administered tetracycline. When two doses of tetracycline are given a number of days apart, two bands of fluorescence will be separated by an interval of unlabeled new bone that has formed during the period between dosesQ. By using two types of tetracyclines, each type produces its distinctive fluorescent colors; which are easily identified, thus simplifying measurement of new formed bone.
• Rate of newly synthesized osteoid material mineralization (bone formation or remodeling) can be estimated by tetracycline labeling (method of choice)Q. Tetracycline HC1, dimethylchlor tetracycline and oxytetracycline are most commonly used for fluorochrome (fluorescent) tetracycline labeling.
• Alizarin red stain, calcein stain and Von kassa (black) stain can also be used to measure rate of bone mineralization but these are inferior (and too toxic for humans) in comparison to tetracycline labeling. So these are only used in animal research.

A i.e. Tetracycline

Ans. is ‘d’ i.e., Tetracycline 

Chemoprophylaxis

o Chemoprophylaxis refers to the administration of a drug for the purpose of preventing disease or infection.
Indications for chemoprophylaxis

Disease                                                 Chemoprophylaxis

Cholera                                                 Tetracycline or furazolidone for house-hold contacts

Conjuncitivitis                                         Erythromycin ophthalmic ointment

Diphtheria                                              Erythromycin (and first dose of vaccine)

Influenza                                               Amantadine (effective only for type A) for contacts suffering from chronic diaeases

Malaria                                                 Chloroquine

Meningitis                                              Sulphadiazine for 4 days only

meningococcal                                       if the strain is shwon to be non-resistant, for household and close community contacts; immunization should be initiate in all cases (against serogrops A,

                                                          and C). However, now rifampicin is the DOC for chemoprophylaxis.

Plague                                                  Tetracycline for contacts of

pneumonic plague

Ans. is ‘a’ i.e., Cholera 

o Tetracycline is the drug of choice for chemoprophylaxis in cholera and plague.

Ans. is ‘a’ i.e., Tetracycline 

• Tetracycline is the drug of choice for chemoprophylaxis.

o Indication

 Chemoprophylaxis is indicated only for household contacts or of a closed community in which cholera has occured.

Remember

Mass chemoprophylaxis is not advised in the total community as it can not stop the spread of cholera. So mass K chemoprophylaxis has no role in controlling the epidemic.

Ans. is ‘a’ i.e., Tetracycline 

Ans. is ‘a’ i.e., Vaccine; ‘b’ i.e., Tetracycline throughout the duty 

C i.e. Tetracycline

• Glucomas Q

-Primary angle closure glucoma (due to corneal edema & stretching Q)

– Open angle glucomaQ

• Acute mucopurulent conjunctivitis Q (due to mucus)
• Corneal scar
• Krukenberg spindle (Pigmentary glucoma)Q
• Cataract Q (lens opacity)
• Vitreous opacities – e.g. haemorrhage, asteroid bodies, synchysis scintillans etc.
• Any haze of ocular media Q
• Contact lens overwear (due to corneal abrasion)
• Too intense exposure to light as in snow blindness
• Asymmetrical placement of intraocular lens in relation to pupillary aperture
• Drugs – acetophenazine, acetyldigitoxin, amiodarone, amodiaquine, amyl nitrite, butaperazine, carphenazine, chloroquine, chlorine dioxide, chlorpromazine, cortisone, deslanoside, dexamethasone, diethazine, digitalis, digitoxin, digoxin, ethopropazine, ethylene diamine, fluorometholone, fluphenazine, gitalin, hydrocortisone, hydroxychloroquine, lanatoside C, medrysone, mesoridazine, methidilazine, methotrimeprazine, methylprednisolone, nitroglycerin, nitronaphalene, oral contraceptives, ouabain, paramethadione, perazine, pericyazine, promazine, promethazine, propiamazine, quinacrine, thiethylperazine, thiopropazine, thioproperazine, thioridazine, trifluoperazine, triflupromazine, trimeprazine, trimethadione and sterile water.

* Tetracycline is not included in this long drug list & haze in ocular media can occur in acute anterior uveitis due to aqueous flare & K.P’s.

C i.e. Tetracycline

Treatment of Trachoma

• Oral tetracycline, doxycycline, azithromycin, clarithromycin, erythromycin, rifampicin & sulfonamides
• Oral tetracycline cannot be given to children < 8 years, pregnant women or nursing mothers.
• Sulfonamides have high risk of stevens Johnson syndrome and erythema multiforme.
• Topical treatment with tetracycline or erythromycin or sulfacetamide (less preffered) is cheaper more effective and has no risk of systemic side effects.

Ans. 0.1%

Ans. A: Tetracycline

The hallmark of LGV is unilateral or bilateral tender lymphadenopathy that dramatically evolves 2 to 6 weeks after the primary lesion.

The involved lymph nodes increase rapidly in size, and pain and erythema are common. If adjacent to one another, several involved lymph nodes may coalesce. The central areas of such lymph nodes can then undergo necrosis. Fluctuant and suppurative lymph nodes then develop, causing the classic ‘bubo’ of LGV.

The bubo may then rupture and drain purulent material, which is associated with relief from symptoms. The ‘groove sign’ characteristic of LGV is seen if both the inguinal and the femoral nodes are involved.

Tetracycline is the first choice drugs for LGV.

Apart from LGV, tetracyclines are drug of choice for:

• STDs-Chlamydial non-specific urethritis/endocervicitis, granuloma inguinale
• Atypical pneumonia
• Cholera
• Brucellosis
• Plague
• Relapsing fever
• Rickettsial infections-typhus, rocky mountain spotted fever, Q fever etc.

Ans. D: Tetracyclines

They are essentially used in the form of drops or ointment for superficial ocular infections such as trachoma. They get deposited in bones and teeth and hence not to be used in children and pregnant/lactating women.

Ans. is ‘d’ i.e., Pneumocystis carinii

Ans. is ‘b’ i.e., Binding to 30 S subunit and inhibits binding of aminoacyl tRNA

Tetracyclines

Tetracyclines are classified into three groups –

• Group I – Tetracycline, oxytetracycline, chlortetracycline.
• Group II – Lymecycline, Demeclocycline.
• Group III – Minocycline, Doxycycline.
• Tetracyclines are bacteriostatic and broad spectrum antibiotics.
• Tetracycline interact with small ribosomal subunits, blocking access of aminoacyl- tRNA to the mRNA-ribos­ome complex.
• Oral absorption of tetracyclines is impaired by food except doxycycline and minocycline which are absorbed completely irrespective of food.
• Most tetracyclines are primarily excreted in urine by glomerular filtration; dose has to be reduced in renal failure; doxycycline is an exception – doxycycline can be used in renal failure.
• Tetracyclines can cross placenta and secreted in milk → contraindicated during pregnancy and lactation.