Amphenicol

Chloramphenicol

A broad-spectrum amphenicol kept for serious infections such as meningitis and typhoid, and used as eye drops for bacterial conjunctivitis.

Drug card

Class: Amphenicol
How it works: Blocking peptidyl transferase on the 50S subunit so no peptide bonds form
Used for: Bacterial meningitis, as a second choice
Typhoid fever
Rickettsial infections
Bacterial conjunctivitis (eye drops or ointment)
Known for: Aplastic anemia, irreversible and often fatal
Gray baby syndrome in newborns

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Mechanism of action

How does chloramphenicol work?

Chloramphenicol, first isolated from Streptomyces venezuelae, binds the 50S subunit reversibly and inhibits peptidyl transferase; it is mainly bacteriostatic. It enters the CSF even without meningeal inflammation, reaching about half the blood level. The liver inactivates it by conjugation with glucuronic acid, a step that is immature in newborns.

Uses

What is chloramphenicol used for?

Bacterial meningitis, as a second choice
Typhoid fever
Rickettsial infections
Bacterial conjunctivitis (eye drops or ointment)
Ear infections (ear drops)
Serious Gram-negative bacteremia when others fail

Side effects

Side effects of chloramphenicol

Aplastic anemia, irreversible and often fatalKnown forSerious
Gray baby syndrome in newbornsKnown forSerious
Dose-related, reversible bone marrow suppressionSerious
Low platelets with bleeding (thrombocytopenic purpura)Serious
AgranulocytosisSerious
Leukemia following aplastic anemiaSerious
Optic neuritis, sometimes with brief blindnessSerious
Peripheral neuritis
Nausea, vomiting and diarrhea
Allergic reactions: fever, rash, angioedema
Herxheimer reaction when treating typhoid
C. difficile colitisSerious

Known for marks what an exam expects you to know it for.

Watch for

Cautions and what sets it apart

Use only when safer antibiotics will not do; it must not be used for trivial infections, colds or prophylaxis.
Check blood counts before and about every 2 days and stop if they fall; normal counts do not rule out later aplastic anemia.
Newborns and premature babies clear it slowly, so blood levels are monitored; UK labels avoid it in pregnancy and breastfeeding.
It boosts warfarin, phenytoin and tolbutamide; phenobarbital and rifampicin lower its levels. Avoid other marrow-suppressing drugs.

Good to know: Even eye drops have rarely been followed by aplastic anemia, so UK eye-drop labels exclude people with past chloramphenicol marrow suppression or a family history of blood disorders.

Remember it

A way to remember it

Chloramphenicol: gray babies and empty marrow.

Newborns cannot conjugate it fast enough, so it builds up and causes gray baby syndrome (a swollen abdomen, ashen cyanosis, circulatory collapse); at any age it can suppress the bone marrow, and rarely it causes aplastic anemia that does not recover.

Written for biofideX

Its class

Amphenicols

Amphenicols bind the 50S ribosomal subunit reversibly and inhibit its peptidyl transferase, so amino acids cannot be linked into a growing chain. They are mainly bacteriostatic and broad in spectrum, covering many Gram-positive and Gram-negative bacteria and rickettsiae. Chloramphenicol reaches the CSF even when the meninges are not inflamed, and the liver inactivates it by joining it to glucuronic acid.

Easily mixed up with tetracyclines and macrolides.

Sources

Checked against

Written for biofideX in plain words, after checking these references:

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.

Practice it

Antibiotics: protein synthesis

Chloramphenicol is one of 10 drugs practiced together here: their classes, how they work, what they treat and what they're known for.

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