Chloramphenicol

Chloramphenicol

Chloramphenicol
Systematic (IUPAC) name
2,2-dichloro-N-[1,3-dihydroxy-1-(4-nitrophenyl)propan-2-yl]acetamide
Clinical data
AHFS/Drugs.com
MedlinePlus
Licence data US FDA:
Pregnancy cat.
Legal status
Routes Topical (ocular), oral, IV, IM
Pharmacokinetic data
Bioavailability 75–90%
Protein binding 60%
Metabolism Hepatic
Half-life 1.6-3.3 hours
Excretion Renal (5-15%), faeces (4%)
Identifiers
CAS number  YesY
ATC code D06 D10 G01 J01 S01 S02 S03 QJ51
PubChem
DrugBank
ChemSpider  YesY
UNII  YesY
KEGG  YesY
ChEBI  YesY
ChEMBL  YesY
Chemical data
Formula C11H12Cl2N2O5 
Mol. mass 323.1320 g/mol
 YesY   

Chloramphenicol (INN) is an antibiotic useful for the treatment of a number of bacterial infections. It is a bacteriostatic; it became available in 1949. It is considered a prototypical broad-spectrum antibiotic, alongside the tetracyclines, and as it is both cheap and easy to manufacture, it is frequently an antibiotic of choice in the developing world.

Chloramphenicol, also known as chlornitromycin, is effective against a wide variety of first-line agent for any infection in developed nations, with the notable exception of topical treatment of bacterial conjunctivitis. Nevertheless, the global problem of advancing bacterial resistance to newer drugs has led to renewed interest in its use.[1] In low-income countries, chloramphenicol is still widely used because it is inexpensive and readily available.

The most serious adverse effect associated with chloramphenicol treatment is bone marrow toxicity, which may occur in two distinct forms: bone marrow suppression, which is a direct toxic effect of the drug and is usually reversible, and aplastic anemia, which is idiosyncratic (rare, unpredictable, and unrelated to dose) and generally fatal.[2]

Use of intravenous chloramphenicol has also been associated with health system.[4]

Pure chloramphenicol

Contents

  • Medical uses 1
    • Spectrum of activity 1.1
  • Adverse effects 2
    • Aplastic anemia 2.1
    • Bone marrow suppression 2.2
    • Leukemia 2.3
    • Gray baby syndrome 2.4
    • Hypersensitivity reactions 2.5
    • Neurotoxic reactions 2.6
  • Pharmacokinetics 3
    • Use in special populations 3.1
    • Dose monitoring 3.2
    • Drug interactions 3.3
    • Drug antagonistic 3.4
  • Mechanism of action 4
  • Resistance 5
  • History 6
  • Formulations 7
    • Intravenous 7.1
    • Oily 7.2
    • Eye drops 7.3
  • References 8
  • Further reading 9
  • External links 10

Medical uses

The original indication of chloramphenicol was in the treatment of tetracycline-resistant cholera.

Because of its excellent blood-brain barrier penetration (far superior to any of the cephalosporins), chloramphenicol remains the first-choice treatment for staphylococcal brain abscesses. It is also useful in the treatment of brain abscesses due to mixed organisms or when the causative organism is not known.

Chloramphenicol is active against the three main bacterial causes of meningitis: Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae. In the West, chloramphenicol remains the drug of choice in the treatment of meningitis in patients with severe penicillin or cephalosporin allergy and general practitioners are recommended to carry intravenous chloramphenicol in their bag. In low-income countries, the WHO recommend oily chloramphenicol as first-line to treat meningitis.

Chloramphenicol has been used in the U.S. in the initial empirical treatment of children with fever and a petechial rash, when the differential diagnosis includes both Neisseria meningitidis septicaemia and Rocky Mountain spotted fever, pending the results of diagnostic investigations.

Chloramphenicol is also effective against Enterococcus faecium, which has led to its being considered for treatment of vancomycin-resistant enterococcus.

Although unpublished, recent research suggests chloramphenicol could also be applied to frogs to prevent their widespread destruction from fungal infections.[5] It has recently been discovered to be a life-saving cure for chytridiomycosis in amphibians.[6] Chytridiomycosis is a fungal disease, blamed for the extinction of one-third of the 120 frog species lost since 1980.

Veterinary Uses

Although its use in veterinary medicine is highly restricted, chloramphenicol still has some important veterinary indications.[7] It is currently considered the most useful treatment of chlamydial disease in koalas.[8][9] The pharmacokinetics of chloramphenicol have been investigated in koalas.[10]

Spectrum of activity

Chloramphenicol has a broad spectrum of activity and has been effective in treating ocular infections caused by a number of bacteria including Staphylococcus aureus, Streptococcus pneumoniae, and Escherichia coli. It is not effective against Pseudomonas aeruginosa. The following susceptibility data represent the

External links

  • Jardetzky, O. (1963). "Studies on the Mechanism of Action of Chloramphenicol". Journal of Biological Chemistry 238 (7): 2498–2508. 

Further reading

  1. ^ Falagas, M. E.; Grammatikos, A. P.; Michalopoulos, A. (October 2008). "Potential of old-generation antibiotics to address current need for new antibiotics". Expert Review of Anti Infective Therapy 6 (5): 593–600.  
  2. ^ a b Rich, M.; Ritterhoff, R.; Hoffmann, R. (December 1950). "A fatal case of aplastic anemia following chloramphenicol (chloromycetin) therapy". Annals of Internal Medicine 33 (6): 1459–1467.  
  3. ^ a b c d e "Drug Insert from DailyMed". Retrieved 18 April 2014. 
  4. ^ "WHO Model List of EssentialMedicines". World Health Organization. October 2013. Retrieved 22 April 2014. 
  5. ^ Griggs, K. (2007-10-30). "'"Frog killer fungus 'breakthrough. BBC News. 
  6. ^ Poulter, R. T. M.; Busby, J. N.; Bishop, P. J.; Butler, M. I.; Speare, R. "Chloramphenicol cures chytridiomycosis" (pdf). NZ Frogs. 
  7. ^ "Chloramphenicol and Congeners". Merck Manuals. Retrieved 31 October 2014. 
  8. ^ Govendir, M (16 May 2011). "Plasma concentrations of chloramphenicol after subcutaneous administration to koalas (Phascolarctos cinereus) with chlamydiosis". Journal of Veterinary Pharmacology and Therapeutics 35: 147–154.  
  9. ^ Griffith, J. (2012). "Diagnosis, treatment and outcomes for koala chlamydiosis at a rehabilitation facility (1995–2005)". Australian Veterinary Journal 90 (90): 457–463.  
  10. ^ Black, Lisa. Journal of Veterinary Pharmacology and Therapeutics 36: 478–485.  
  11. ^ http://antibiotics.toku-e.com/antimicrobial_507.html
  12. ^ Carone, BR; Xu, T; Murphy, KC; Marinus, MG (Jan 2014). "High incidence of multiple antibiotic resistant cells in cultures of in enterohemorrhagic Escherichia coli O157:H7.". Mutation research 759: 1–8.  
  13. ^ Moore, AM; Patel, S; Forsberg, KJ; Wang, B; Bentley, G; Razia, Y; Qin, X; Tarr, PI; Dantas, G (2013). "Pediatric fecal microbiota harbor diverse and novel antibiotic resistance genes.". PLoS ONE 8 (11): e78822.  
  14. ^ Nagao, T.; Mauer, A. (July 1969). "Concordance for drug-induced aplastic anemia in identical twins". New England Journal of Medicine 281 (1): 7–11.  
  15. ^ Hammett-Stabler, C.; Johns, T. (May 1988). "Laboratory guidelines for monitoring of antimicrobial drugs". Clinical Chemistry 44 (5): 1129–1140.  
  16. ^ Holt, R. (1967). "The bacterial degradation of chloramphenicol". Lancet 289 (7502): 1259–1260.  
  17. ^ Wallerstein, R.; Condit, P.; Kasper, C.; Brown, J.; Morrison, F. (June 1969). "Statewide study of chloramphenicol therapy and fatal aplastic anemia". JAMA 208 (11): 2045–2050.  
  18. ^ a b Lancaster, T.; Stewart, A. M.; Jick, H. (1998). "Risk of serious haematological toxicity with use of chloramphenicol eye drops in a British general practice database". British Medical Journal 316 (7132): 667.  
  19. ^ Yunis AA (September 1989). "Chloramphenicol toxicity: 25 years of research". Am. J. Med. 87 (3N): 44N–48N.  
  20. ^ Morley, Alec; Trainor, Kevin; Remes, Judith (1 April 1976). "Residual Marrow Damage: Possible Explanation for Idiosyncrasy to Chloramphenicol". British Journal of Haematology 32 (4): 525–532.  
  21. ^ Shu, X.; Gao, Y.; Linet, M.; Brinton, L.; Gao, R.; Jin, F.; Fraumeni, J. (October 1987). "Chloramphenicol use and childhood leukaemia in Shanghai". Lancet 2 (8565): 934–937.  
  22. ^ McIntyre, J.; Choonara, I. (2004). "Drug toxicity in the neonate". Biology of the Neonate 86 (4): 218–221.  
  23. ^ Piñeiro-Carrero, V.; Piñeiro, E. (2004). "Liver" (pdf). Pediatrics 113 (4 Supplement): 1097–1106.  
  24. ^ Feder, H. (1986). "Chloramphenicol: what we have learned in the last decade". Southern Medical Journal 79 (9): 1129–1134.  
  25. ^ Mulhall, A.; de Louvois J.; Hurley, R. (1983). "Chloramphenicol toxicity in neonates: its incidence and prevention". British Medical Journal (Clinical Research Edition) 287 (6403): 1424–1427.  
  26. ^ Forster, J.; Hufschmidt, C.; Niederhoff, H.; Künzer, W. (1985). "[Need for the determination of chloramphenicol levels in the treatment of bacterial-purulent meningitis with chloramphenicol succinate in infants and small children]". Monatsschrift Kinderheilkunde (in German) 133 (4): 209–213.  
  27. ^ Harold M. Silverman, Pharm.D. (editor-in-chief), ed. (2006). "Iron Supplements". Pill Book, The (12th revised ed.). New York: Bantam Dell. pp. 593–596.  
  28. ^ kidsgrowth.org --> Drugs and Other Substances in Breast Milk Retrieved on June 19, 2009
  29. ^ Hammett-Stabler, C; Johns, T. (May 1988). "Laboratory guidelines for monitoring of antimicrobial drugs". Clinical Chemistry 44 (5): 1129–1140.  
  30. ^ "Chloramphenicol (Lexi-Drugs)". Lexi-Comp Online. Retrieved 18 April 2014. 
  31. ^ [1] June 2005. Royal Pharmaceutical Society of Great Britain (RPSGB)
  32. ^ Park, J. Y.; Kim, K. A.; Kim, S. L. (November 2003). "Chloramphenicol Is a Potent Inhibitor of Cytochrome P450 Isoforms CYP2C19 and CYP3A4 in Human Liver Microsomes". Antimicrobial Agents and Chemotherapy 47 (11): 3464–3469.  
  33. ^ "Facts for prescribers (Fakta för förskrivare)" (in Swedish). FASS - Swedish National Drug Formulary. 
  34. ^ "Antagonistic effect of chloramphenicol in combination with cefotaxime or ceftriaxone". Retrieved August 25, 2014. 
  35. ^ "Chloramphenicol". The Merck Manual. Merck. 
  36. ^ Jardetzky, O. (July 1963). "Studies on the Mechanism of Action of Chloramphenicol - The Conformation of Chloramphenicol in Solution" (pdf). The Journal of Biological Chemistry 238 (7): 2498–2508.  
  37. ^ Wolfe, A. D.; Hahn, F. E. (1965). "Mode of Action of Chloramphenicol. IX. Effects of Chloramphenicol Upon a Ribosomal Amino Acid Polymerization System and Its Binding to Bacterial Ribosome". Biochimica et Biophysica Acta 95: 146–155.  
  38. ^ Hahn, F. E.; Wisseman, C. L. Jr.; Hopps, H. E. (1955). "Mode of Action of Chloramphenicol III. : Action of Chloramphenicol on Bacterial Energy Metabolism". Journal of Bacteriology 69 (2): 215–223.  
  39. ^ "Chloramphenicol spectrum of bacterial susceptibility and Resistance". Retrieved 15 May 2012. 
  40. ^ R.L. Rosenthal, A. Blackman (1965). "Bone-marrow hypoplasia following use of chloramphenicol eye drops". JAMA 191 (3): 136–137.  
  41. ^ Fraunfelder, F.; Fraunfelder, F (September 2013). "Restricting Topical Ocular Chloramphenicol Eye Drop Use in the United States. Did We Overreact?". American Journal of Ophtalmology 156 (3): 420–422.  
  42. ^ Glazko, A. J.; Dill, W. A.; Kinkel, A. W. (1977). "Absorption and excretion of parenteral doses of chloramphenicol sodium succinate in comparison with per oral doses of chloramphenicol (abstract)". Clinical Pharmacological Therapy 21: 104. 
  43. ^ Bhutta, Z.; Niazi, S.; Suria, A. (March–April 1992). "Chloramphenicol Clearance in Typhoid Fever: Implications for Therapy". Indian Journal of Pediatry 59 (2): 213–219.  
  44. ^ Lewis, R. F.; Dorlencourt, F.; Pinel, J. (1998). "Long-acting oily Chloramphenicol for Meningococcal Meningitis". Lancet 352 (9130): 823.  
  45. ^ Rey, M.; Ouedraogo, L.; Saliou, P.; Perino, L. (1976). "Traitement minute de la méningite cérébrospinale épidémique par injection intramusculaire unique de chloramphénicol (suspension huileuse)". Médecine et Maladies Infectieuses (in French) 6 (4): 120–124.  
  46. ^ Wali, S.; Macfarlane, J.; Weir, W.; Cleland, P.; Ball, P.; Hassan-King, M.; Whittle, H.; Greenwood, B. (1979). "Single injection treatment of meningococcal meningitis. 2. Long-acting chloramphenicol". Transactions of the Royal Society for Tropical Medicine and Hygiene 73 (6): 698–702.  
  47. ^ Puddicombe, J.; Wali, S.; Greenwood, B. (1984). "A field trial of a single intramuscular injection of long-acting chloramphenicol in the treatment of meningococcal meningitis". Transactions of the Royal Society for Tropical Medicine and Hygiene 78 (3): 399–403.  
  48. ^ Pécoulm B.; Varaine, F.; Keita, M.; Soga, G.; Djibo, A.; Soula, G.; Abdou, A.; Etienne, J.; Rey, M. (October 1991). "Long-acting chloramphenicol versus intravenous ampicillin for treatment of bacterial meningitis". Lancet 338 (8771): 862–866.  
  49. ^ Nathan, N.; Borel, T.; Djibo, A. (2005). "Ceftriaxone as effective as long-acting chloramphenicol in short-course treatment of meningococcal meningitis during epidemics: a randomised non-inferiority study". Lancet 366 (9482): 308–313.  

References

Chloramphenicol is still widely used in topical preparations (ointments and eye drops) for the treatment of bacterial conjunctivitis. Isolated case reports of aplastic anaemia following use of chloramphenicol eyedrops exist, but the risk is estimated to be less than one in 224,716 prescriptions.[18] In Mexico, this is the treatment used prophylactically in newborns.

Eye drops

Oily chloramphenicol is recommended by the World Health Organization as the first-line treatment of meningitis in low-income countries, and appears on the WHO essential drugs list. It was first used to treat meningitis in 1975[45] and numerous studies since have demonstrated its efficacy.[46][47][48] It is the cheapest treatment available for meningitis (US$5 per treatment course, compared to US$30 for ampicillin and US$15 for five days of ceftriaxone). It has the great advantage of requiring only a single injection, whereas ceftriaxone is traditionally given daily for five days. This recommendation may yet change, now that a single dose of ceftriaxone (cost US$3) has been shown to be equivalent to one dose of oily chloramphenicol.[49]

Oily chloramphenicol (or chloramphenicol oil suspension) is a long-acting preparation of chloramphenicol first introduced by Roussel in 1954; marketed as Tifomycine, it was originally used as a treatment for typhoid. Roussel stopped production of oily chloramphenicol in 1995; the International Dispensary Association has manufactured it since 1998, first in Malta and then in India from December 2004.[44]

Oily

The intravenous (IV) preparation of chloramphenicol is the succinate ester, because pure chloramphenicol does not dissolve in water. This creates a problem: Chloramphenicol succinate ester is an inactive prodrug and must first be hydrolysed to chloramphenicol; however, the hydrolysis process is often incomplete, and 30% of the dose is lost and removed in the urine. Serum concentrations of IV chloramphenicol are only 70% of those achieved when chloramphenicol is given orally.[42] For this reason, the dose needs to be increased to 75 mg/kg/day when administered IV to achieve levels equivalent to the oral dose.[43]

Intravenous

In molecular biology, chloramphenicol is prepared as 25–50 mg/ml stock in ethanol.

Manufacture of oral chloramphenicol in the U.S. stopped in 1991, because the vast majority of chloramphenicol-associated cases of aplastic anaemia are associated with the oral preparation. No oral formulation of chloramphenicol is now available in the U.S.

Chloramphenicol is available as 250-mg capsules or as a liquid (125 mg/5 ml). In some countries, it is sold as chloramphenicol palmitate ester (CPE). CPE is inactive, and is hydrolysed to active chloramphenicol in the small intestine. No difference in bioavailability is noted between chloramphenicol and CPE.

Formulations

In 2007, the accumulation of reports associating aplastic anemia and blood dyscrasia with chloramphenicol eye drops lead to the classification of “probable” according to World Health Organization criteria, based on the known published case reports and the spontaneous reports submitted to the National Registry of Drug-Induced Ocular Side Effects.[41]

The topical formulation of chloramphenicol was commonly used as eye drops as first-line treatment of conjunctivitis. The first fatality from eye drops was reported in 1955.[40]

Chloramphenicol was originally derived from the bacterium Streptomyces venezuelae, isolated by David Gottlieb, and introduced into clinical practice in 1949, under the trade name Chloromycetin. It was the first antibiotic to be manufactured synthetically on a large scale.

History

Currently, some Enterococcus faecium and Pseudomonas aeruginosa strains are resistant to chloramphenicol. Some Veillonella spp. and Staphylococcus capitis strains have also developed resistance to chloramphenicol to varying degrees.[39]

Chloramphenicol resistance may be carried on a plasmid that also codes for resistance to other drugs. One example is the ACCoT plasmid (A=ampicillin, C=chloramphenicol, Co=co-trimoxazole, T=tetracycline), which mediates multiple-drug resistance in typhoid (also called R factors).

Three mechanisms of resistance to chloramphenicol are known: reduced membrane permeability, mutation of the 50S ribosomal subunit, and elaboration of chloramphenicol acetyltransferase. It is easy to select for reduced membrane permeability to chloramphenicol in vitro by serial passage of bacteria, and this is the most common mechanism of low-level chloramphenicol resistance. High-level resistance is conferred by the cat-gene; this gene codes for an enzyme called chloramphenicol acetyltransferase, which inactivates chloramphenicol by covalently linking one or two acetyl groups, derived from acetyl-S-coenzyme A, to the hydroxyl groups on the chloramphenicol molecule. The acetylation prevents chloramphenicol from binding to the ribosome. Resistance-conferring mutations of the 50S ribosomal subunit are rare.

Resistance

Chloramphenicol is a bacteriostatic by inhibiting protein synthesis. It prevents protein chain elongation by inhibiting the peptidyl transferase activity of the bacterial ribosome. It specifically binds to A2451 and A2452 residues in the 23S rRNA of the 50S ribosomal subunit, preventing peptide bond formation.[35] While chloramphenicol and the macrolide class of antibiotics both interact with ribosomes, chloramphenicol is not a macrolide. It directly interferes with substrate binding, whereas macrolides sterically block the progression of the growing peptide. [36] [37] [38]

Mechanism of action

Bacteriostatic Chloramphenicol is antagonistic with bactericidal Cephalosporin and should be avoided in the treatment of infections.[34]

Drug antagonistic

Chloramphenicol is a potent inhibitor of the cytochrome P450 isoforms CYP2C19 and CYP3A4 in the liver.[32] Inhibition of CYP2C19 causes decreased metabolism and therefore increased levels of, for example, antidepressants, antiepileptics, proton pump inhibitors, and anticoagulants if they are given concomitantly. Inhibition of CYP3A4 causes increased levels of, for example, calcium channel blockers, immunosuppressants, chemotherapeutic drugs, benzodiazepines, azole antifungals, tricyclic antidepressants, macrolide antibiotics, SSRIs, statins, cardiac antiarrhythmics, antivirals, anticoagulants, and PDE5 inhibitors.[3][33]

Administration of chloramphenicol concomitantly with bone marrow depressant drugs is contraindicated, although concerns over aplastic anaemia associated with ocular chloramphenicol have largely been discounted.[31]

Drug interactions

Plasma levels of chloramphenicol must be monitored in neonates and patients with abnormal liver function. Plasma levels should be monitored in all children under the age of four, the elderly, and patients with renal failure. Because efficacy and toxicity of chloramphenicol are associated with a maximum serum concentration, peak levels (one hour after the intravenous dose is given) should be 10-20 mcg/ml with toxicity >40 mcg/ml; trough levels (taken immediately before a dose) should be 5-10 mcg/ml.[29][30]

Dose monitoring

Chloramphenicol passes into breast milk, so should therefore be avoided during breast feeding, if possible.[28]

The majority of the chloramphenicol dose is excreted by the kidneys as the inactive metabolite, chloramphenicol glucuronate. Only a tiny fraction of the chloramphenicol is excreted by the kidneys unchanged. Plasma levels should be monitored in patients with renal impairment, but this is not mandatory. Chloramphenicol succinate ester (an intravenous prodrug form) is readily excreted unchanged by the kidneys, more so than chloramphenicol base, and this is the major reason why levels of chloramphenicol in the blood are much lower when given intravenously than orally.

Chloramphenicol is metabolized by the liver to chloramphenicol glucuronate (which is inactive). In liver impairment, the dose of chloramphenicol must therefore be reduced. No standard dose reduction exists for chloramphenicol in liver impairment, and the dose should be adjusted according to measured plasma concentrations.

Use in special populations

Chloramphenicol increases the absorption of iron.[27]

Chloramphenicol is extremely lipid soluble; it remains relatively unbound to protein and is a small molecule. It has a large apparent volume of distribution and penetrates effectively into all tissues of the body, including the brain. Distribution is not uniform, with highest concentrations found in the liver and kidney, with lowest in the brain and cerebrospinal fluid.[3] The concentration achieved in brain and cerebrospinal fluid is around 30 to 50%, even when the meninges are not inflamed; this increases to as high as 89% when the meninges are inflamed.

Pharmacokinetics

Headache, mild depression, mental confusion, and delirium have been described in patients receiving chloramphenicol. Optic and peripheral neuritis have been reported, usually following long-term therapy. If this occurs, the drug should be promptly withdrawn.[3]

Neurotoxic reactions

Fever, macular and vesicular rashes, angioedema, urticaria, and anaphylaxis may occur. Herxheimer’s reactions have occurred during therapy for typhoid fever.[3]

Hypersensitivity reactions

Intravenous chloramphenicol use has been associated with the so-called gray baby syndrome.[22] This phenomenon occurs in newborn infants because they do not yet have fully functional liver enzymes (i.e. UDP-glucuronyl transferase), so chloramphenicol remains unmetabolized in the body.[23] This causes several adverse effects, including hypotension and cyanosis. The condition can be prevented by using the drug at the recommended doses, and monitoring blood levels.[24][25][26]

Gray baby syndrome

Leukemia, a cancer of the blood or bone marrow, is characterized by an abnormal increase of immature white blood cells. The risk of childhood leukemia is increased, as demonstrated in a Chinese case-controlled study,[21] and the risk increases with length of treatment.

Leukemia

Chloramphenicol may cause bone marrow suppression during treatment; this is a direct toxic effect of the drug on human mitochondria.[19] This effect manifests first as a fall in hemoglobin levels, which occurs quite predictably once a cumulative dose of 20 g has been given. The anaemia is fully reversible once the drug is stopped and does not predict future development of aplastic anaemia. Studies in mice have suggested existing marrow damage may compound any marrow damage resulting from the toxic effects of chloramphenicol.[20]

Bone marrow suppression

Thiamphenicol, a related compound with a similar spectrum of activity, is available in Italy and China for human use, and has never been associated with aplastic anaemia . Thiamphenicol is available in the U.S. and Europe as a veterinary antibiotic, but is not approved for use in humans.

The most serious side effect of chloramphenicol treatment is aplastic anaemia.[2] This effect is rare and is generally fatal. No treatment is available and no way exists to predict who may or may not get this side effect. The effect usually occurs weeks or months after treatment has been stopped, and a genetic predisposition may be involved.[14] It is not known whether monitoring the blood counts of patients can prevent the development of aplastic anaemia, but patients are recommended to have a baseline blood count with a repeat blood count every few days while on treatment.[15] Chloramphenicol should be discontinued if the complete blood count drops below 2.5 x 10 cells/l. The highest risk is with oral chloramphenicol[16] (affecting 1 in 24,000–40,000)[17] and the lowest risk occurs with eye drops (affecting less than one in 224,716 prescriptions).[18]

Aplastic anemia

Adverse effects

Each of these concentrations is dependent upon the bacterial strain being targeted. Some strains of E. coli, for example, show spontaneous emergence of chloramphenicol resistance.[12][13]

  • Escherichia coli: 0.015 - 10,000 μg/ml
  • Staphylococcus aureus: 0.06 - >128 μg/ml
  • Streptococcus pneumoniae: 2 - 16 μg/ml

[11]