Chemical formula: C₂₃H₂₇N₃O₇ Molecular mass: 457.476 g/mol PubChem compound: 54675783
Minocycline hydrochloride has a spectrum of activity and mode of action similar to that of tetracycline hydrochloride, but it is more active against many species. In addition, it is reported to be effective in vitro, against some tetracycline resistant staphylococci, streptococci and certain strains of tetracycline-resistant Escherichia coli and Haemophilus influenzae.
Minocycline is a semi-synthetic derivative of tetracycline.
The general MIC breakpoint to identify organisms susceptible to minocycline is ≥ 0.5 mg/l. All organisms for which the MIC of minocycline is ≥ 1 mg/l are considered resistant (European Committee on Antimicrobial Susceptibility Testing (EUCAST), 2004).
The prevalence of resistance may vary geographically and with time for selected species and local information on resistance is desirable. Minocycline is usually active in vitro against Propionibacterium acnes, which is implicated in the pathogenesis of acne.
Bacterial resistance to the tetracyclines is now common in some species and usually involves cross-resistance between the different tetracyclines.
Minocycline is readily absorbed from the GI tract and is not significantly affected by the presence of food or moderate amounts of milk although absorption is impaired by the concomitant administration of iron salts or antacids containing calcium, magnesium or aluminium salts. Normal doses of 200mg followed by 100mg every 12 hours produced plasma concentrations within the range of 1-4μg/ml.
It is more lipid-soluble than doxycycline and the other tetracyclines and is widely distributed in body tissues and fluids, including the cerebrospinal fluid. A higher ratio of CSF to blood concentrations has been reported with minocycline than with doxycycline. It crosses the placenta and diffuses into milk of nursing mothers. About 75% of minocycline in the circulation is bound to plasma proteins. The plasma half-life tends to be prolonged in patients with severe renal impairment. It has a lower renal clearance than doxycycline and its plasma half-life ranges from 11-23 hours. It penetrates well into thyroid, lung and liver tissues and in most instances tissue levels exceed serum levels. It also appears in tears and saliva.
In contrast to most tetracyclines, minocycline appears to undergo some metabolism in the liver, mainly to 9-hydroxyminocycline. It is also excreted in bile.
About a third of the drug may be excreted unchanged and although figures vary widely, about a third of this unchanged drug may appear in the urine and two thirds in the faeces.
Not applicable.
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