Chloramphenicol is a broad-spectrum antibiotic that is now used only as a backup antibiotic for severe bacterial infections that cannot be controlled otherwise because of the potential for severe side effects. It can cause aplastic anemia, which is life-threatening.
What is chloramphenicol?
Chloramphenicol is a broad-spectrum antibiotic that, because of the possibility of aplastic anemia as an occurring side effect, is now used only as a backup antibiotic. It was first obtained from the bacterium streptomyces venezuelae in 1947. Today it is only produced fully synthetically. Life-threatening aplastic anemia can occur during treatment with chloramphenicol. For this reason, it is not used widely, but only as a reserve antibiotic in bacterial infections that cannot be controlled otherwise. In principle, however, it has a broad spectrum of activity against Gram-positive and Gram-negative bacteria. Topical use is not recommended because systemic side effects are possible; however, chloramphenicol is still approved for use in dermatological medicines, eye and ear drops, and eye ointments. It should be noted, however, that the incidence of systemic side effects with topical treatment is very low. Thus, individual consideration should always be given. The risks of topical application of chloramphenicol are controversially discussed among experts. In veterinary medicine, chloramphenicol is used against chytridiomycosis, a fungal disease in amphibians. Thus, it is also effective against chytrid fungus (a fungus).
Pharmacological action
Chloramphenicol prevents the translation of mRNA into amino acids. Thus, it is a so-called translation inhibitor. This leads to inhibition of the breakdown of bacterial proteins and thus inhibition of bacterial growth and multiplication. Chloramphenicol is thus a bacteriostatic antibiotic. It is well absorbed by tissues, including the placenta (placenta) and breast milk. When administered orally, bioavailability is 80%; when injected intramuscularly, it is 70%. Plasma protein binding is between 50 and 60%, and plasma half-life is 1.5 to 3.5 hours. In renal and hepatic dysfunction, the plasma half-life is prolonged, which should be taken into account in dosing. Metabolism occurs hepatically, almost exclusively via glucuronidation. Elimination is subsequently renal.
Medical application and use
Chloramphenicol is used only as a backup antibiotic when other therapeutic options are either unavailable or have failed because of its unfavorable side-effect profile. Thus, the main indications are severe bacterial infections that cannot be controlled in any other way. These indications for chloramphenicol include typhoid, paratyphoid, dysentery, diphtheria, malaria, and rickettsial infections. In addition to the above indications, chloramphenicol can be used as a reserve antibiotic for meningitis caused by pneumococci or Haemophilus influenzae because of its good cerebrospinal fluid (CSF) penetrability. Topically, chloramphenicol is used to treat conjunctivitis and corneal infections. Chloramphenicol is also used in blepharitis (inflammation of the eyelids). Furthermore, it is used for infections of the skin and eczema.
Risks and side effects
The most serious possible side effect of chloramphenicol is so-called aplastic anemia. It rarely occurs, but it is life-threatening. In aplastic anemia, damage occurs to the bone marrow, resulting in hardly any blood cells being produced in the bone marrow. Aplastic anemia can occur even weeks and months after therapy with chloramphenicol. Signs of this anemia include extreme fatigue, bleeding, and possibly severe infection. Other side effects include allergic reactions when used topically, which may manifest as itching, a reddening of the skin, skin irritation, and swelling. When used systemically, Gray’s syndrome may occur in newborns. Furthermore, Herxheimer reaction is a possible side effect. It should be noted that chloramphenicol interacts with anticoagulants, methotrexate and sulfonylureas. There is an amplification of effect in this case. Barbiturates and phenytoin lead to a reduced efficacy of chloramphenicol.When taking oral contraceptives (e.g. the “birth control pill”), it should be noted that chloramphenicol impairs the efficacy of the preparation. Additional contraception should therefore be used. Chloramphenicol is contraindicated in newborns. Furthermore, there are contraindications in severe hepatic insufficiency, pregnancy and during lactation. Preparations containing chloramphenicol are available only on prescription. Chloramphenicol may not be used in food-producing animals in the EU.