The cloranfenicol is especially bacteriostatic. It joins the subunit 50S of the ribosoma and inhibits this way the synthesis of bacterial proteins. It has a wide activity bogey against coconuts and bacilli grampositivos and gramnegativos (including the anaerobic ones), Rickettsia, Mycoplasma and. The treatment with cloranfenicol must limit itself to serious infections in which other medicines are less effective or more poisonous, because in rare occasions it causes anemia aplásica, a complication in mortal potency.
Pharmacology. The cloranfenicol is absorbed well for v.o. but not for route i.m. For the treatment parenteral it is necessary to use the route i.v. The medicine is distributed extensively by the corporal liquids and obtains therapeutic concentrations in LCR. The cloranfenicol is even metabolized in the liver glucorónido inactively. Both the cloranfenicol and the metabolito glucorónido are excreted by the urine. Due to the hepatic metabolism, the active cloranfenicol does not accumulate in the patients' plasma with renal insufficiency.
Indications. The cloranfenicol is one of the medicines of election for 1) the fever typhoid and other serious infections for Salmonella; 2) the meningitis for capable Haemophilus influenzae, meningococos or pneumococcus, when it is not possible to use an antibiotic β-lactámico; 3) the serious infections for B. fragilis, and 4) the infection rickettsiósica that does not answer to the tetraciclina or when it is not possible to use the tetraciclina. The cloranfenicol is effective in the meningitis for capable vines of H. influenzae, meningococos and pneumococcus, but it proves to be relatively ineffective in the meningitis for Escherichia coli and other enterobacteriáceas.
Adverse reactions. The cloranfenicol can cause two types of depression of the bone marrow: a reversible interference dependent on the dose with the metabolism of the iron and an irreversible idiosyncratic form of anemia aplásica. It is probable that the reversible form happens with high doses, in case of long treatment and in patients with hepatic illness: the iron rises sérico and the saturation of the capacity of reception of the iron, they diminish the reticulocitos and it appears vacuolización of the precursors eritrocitarios, anemia, leucopenia and trombocitopenia. The anemia aplásica idiosyncratic irreversible happens in <1:25.000 patients treated with cloranfenicol. The beginning of the symptoms can be late even after suspending the treatment.
The hypersensitivity reactions are infrequent. The long use of cloranfenicol can drive to neuritis optical and peripheral. Morning sickness, vomiting and diarrhea can appear.
The gray syndrome of the newborn baby (v. also antibacterial Treatment in Infections neonatales, cap. 260 ), often mortal, he keeps relation at high blood levels for incapability of the immature liver to metabolize the cloranfenicol, and can appear with standard dose.
Administration and dosage. The cloranfenicol dose for the adults and the children is 50 mg / kg / d v.o. or i.v. in fractional doses every 6 hs In the meningitis, and sometimes in other serious infections, from 75 to 100 are used mg / kg / d in fractional doses. To avoid the gray syndrome of the newborn baby, the children ¾1 month must not receive> 25 mg / kg / d initially. The dosage will fit to obtain levels séricos from 10 to 30 μg/ml (31 to 93 μmol/l) in order to avoid the toxicity, especially in new-born, nursing premature babies and patients with hepatic illness. The cloranfenicol does not owe to administer the women during the childbearing. It is not also necessary to use for local route due to the possibility of absorption of small quantities that, in rare occasions, can cause anemia aplásica.