Minocycline : Therapeutic uses, Dosage & Side Effects
Minocycline is an semisynthetic broad spectrum tetracycline antibiotic.
Dose : 100-200 mg OD
Route : Oral
Onset of action : ?
Plasma Half-life : 18-24 hours
Duration of action : ?
Bioavailability : 100%
Plasma protein binding : High
Metabolism : Hepatic
Pregnancy risk category : D
Chemical formula : C23H27N3O7
IUPAC name : (2E,4S,4aR,5aS,12aR)-2-(Amino-hydroxy-methylidene)-4,7-bis(dimethylamino)-10,11,12a-trihydroxy-4a,5,5a,6- tetrahydro-4H-tetracene-1,3,12-trione
Trade name : Cyanomycin, Minocin, Dynacin, Solodyn, Vectrin, Myrac, Minomycin, Akamin
Antibacterial spectrum : Minocycline is active against both gram positive & gram negative bateria.
Therapeutic uses : Minocycline is indicated for treatment of various bacterial infections, such as urinary tract infections, respiratory infections, skin infections, severe acne, gonorrhea, tick fever, chlamydia, Amoebic dysentery, Anthrax, Plague, Cholera, Ehrlichiosis, Hidradenitis suppurativa, HIV—for use as an adjuvant to HAART, Periodontal disease, Perioral dermatitis, Rocky Mountain spotted fever, Rosacea, Syphilis (when penicillin cannot be given), rectal infections, and others.
Mechanism of action : Tetracyclines enter susceptible organisms via passive diffusion & by an energy-dependent transport protein mechanism unique to the bacterial inner cytoplasmic membrane. Tetracyclines concentrate intracellularly in susceptible organisms. The drugs bind reversibly to the 30S subunit of the bacterial ribosome. This action prevents binding of aminoacyl-t-RNA to the mRNA–ribosome complex, thereby inhibiting bacterial protein synthesis.
Side effects : Minocycline may cause following side effects :
- Irritative effects : Epigastric pain, nausea, vomiting, diarrhoea. The irritative diarrhoea is to be distinguished from that due to superinfection.
- Thrombophlebitis of the injected vein.
- Kidney damage (prominent only in the presence of existing kidney disease).
- A reversible Fancony syndrome like condition is produced by outdated tetracyclines due to proximal tubular damage caused by degraded products-epitetracycline,
anhydrotetracycline and epianhydrotetracycline. Exposure to acidic pH, moisture and heat favours such degradation.
- Phototoxicity (Distortion of nails occurs occasionally)
- Liver damage : Fatty infiltration of liver and jaundice occurs occasionally.
- Antianabolic effect : Reduce protein synthesis and cause an overall catabolic effect. It induces negative nitrogen balance and can increase blood urea.
- Increased intracranial pressure is noted insome infants.
- Hypersensitivity reactions (infrequent) : Skin rashes, urticaria, glossitis, pruritus ani and vulvae, even exfoliative dermatitis have been reported. Complete cross sensitization is exhibited by different tetracyclines.
- Vestibular toxicity : Minocycline has produced ataxia, vertigo and nystagmus, which subside when the drug is discontinued.
- Superinfection : Tetracyclines are the most common antibiotics responsible for superinfections, because they cause marked suppression of the resident flora.
- Teeth and bones : Tetracyclines have chelating property. Calcium-tetracycline chelate gets deposited in developing teeth and bone. Given from midpregnancy to 5 months of extrauterine life, the deciduous teeth are affected: brown discolouration, ill-formed teeth, more susceptible to caries. Tetracyclines given between 3 months and 6 years of age affect the crown of permanent anterior dentition. Repeated courses are more damaging.
Given during late pregnancy or childhood, tetracyclines can cause temporary suppression of bone growth. The ultimate effect on stature is mostly insignificant, but deformities and reduction in height are a possibility with prolonged use.
Drug Interactions : Minocycline may interact with following drugs :
- Contraindicated in persons who have shown hypersensitivity to any of the Tetracyclines.
- Tetracyclines should not be used in pregnant or breast-feeding women or in children less than 8 years of age.
For detailed query or in case of uncertainty, Always consult your doctor or pharmacist.