Ceftriaxone chemical structure, 2D skeletal formula, C18H18N8O7S3

Ceftriaxone Chemical Structure

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1. Identification

Summary

Ceftriaxone is a parenteral third-generation cephalosporin for susceptible systemic infections, including meningitis and gonorrhea; long elimination half-life enables once-daily dosing in many indications.

Brand Names

Rocephin; multiple generics

Name

Ceftriaxone

Background

IV/IM only; high protein binding with concentration dependence; dual renal–biliary elimination; avoid IV calcium co-administration in neonates; risk of biliary “sludge.”

Modality

Small molecule

Groups

Approved; prescription

Structure

Ceftriaxone chemical structure, 2D skeletal formula, C18H18N8O7S3
Ceftriaxone 2D chemical structure (cephem β-lactam with methoxyimino and aminothiazole groups). Formula C18H18N8O7S3; IUPAC long name; CAS 73384-59-5.

Weight

~554.57 g/mol (free acid/base)

Chemical Formula

C₁₈H₁₈N₈O₇S₃

Synonyms

(6R,7R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2-(methoxyimino)acetamido]-3-[(2-methyl-1,2,5,6-tetrahydro-1,2,4-triazin-3-yl)thio]methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid

External IDs

CAS (base): 73384-59-5; PubChem CID: 5479530; UNII (base): 75J73V1629; ATC: J01DD04

2. Pharmacology

Indication

Susceptible infections: community-acquired and nosocomial pneumonia, meningitis, acute otitis media, skin/soft-tissue, intra-abdominal, bone/joint, urinary tract, septicemia, pelvic inflammatory disease, and uncomplicated gonorrhea; surgical prophylaxis per label.

Associated Conditions

Bacterial meningitis (including S. pneumoniae, N. meningitidis, H. influenzae), disseminated gonococcal infection, typhoid fever (regional guidance), Lyme neuroborreliosis (guideline-dependent).

Associated Therapies

With other agents per site/severity (e.g., vancomycin for empirical meningitis; metronidazole for intra-abdominal sepsis).

Contraindications & Blackbox Warnings

No boxed warning. Contraindicated in neonates ≤28 days requiring IV calcium-containing solutions (risk of precipitation) and in hyperbilirubinemic neonates (bilirubin displacement). Severe hypersensitivity to cephalosporins or serious β-lactam allergy.

Pharmacodynamics

β-lactam PBP inhibition → blocked peptidoglycan crosslinking → bactericidal cell-wall action; time-dependent killing.

Mechanism of action

Covalent acylation of PBPs; activity against many Enterobacterales, Neisseria, H. influenzae, streptococci; limited activity vs Pseudomonas (not a antipseudomonal cephalosporin).

Absorption

Not orally available; complete systemic availability after IV/IM administration.

Volume of distribution

~5.8–13.5 L in healthy adults; penetrates CSF with inflamed meninges.

Protein binding

~95% → 85% over rising plasma concentrations (concentration-dependent, reversible).

Metabolism

Minimal.

Route of elimination

~33–67% renal unchanged; remainder biliary/fecal (enterohepatic cycling).

Half-life

~5.8–8.7 h in healthy adults (longer in neonates/elderly).

Clearance

Plasma clearance ~0.58–1.45 L/h; renal clearance ~0.32–0.73 L/h across 0.15–3 g dosing range.

Adverse Effects

Injection-site reactions, diarrhea, rash, eosinophilia/thrombocytosis; C. difficile–associated diarrhea; biliary pseudolithiasis/sludge; rare hemolytic anemia, severe cutaneous reactions.

Toxicity

Precipitation with IV calcium in neonates (lung/kidney deposition); manage exposures supportively.

Pathways

PBP binding; dual elimination (renal/biliary).

Pharmacogenomic Effects/ADRs

None established for patient selection.

3. Interactions

Drug Interactions

IV calcium products in neonates ≤28 days: contraindicated (precipitation).
Vitamin K antagonists: possible ↑ INR; monitor.
Aminoglycosides: potential synergy (do not co-mix in same IV line).
Bacteriostatic antibiotics: possible antagonism in severe infections (clinical context dependent).

Food Interactions

Not applicable (parenteral use).

4. Categories

ATC Codes

J01DD04 (third-generation cephalosporins)

Drug Categories

Third-generation cephalosporin; β-lactam; Antibacterial; Small molecule

Chemical Taxonomy

Cephem core with methoxyimino and aminothiazole moieties; thiotriazinone-thio side chain.

Affected organisms

Humans (therapeutic use); target bacteria susceptible to β-lactams

5. Chemical Identifiers

UNII

75J73V1629 (ceftriaxone, base)

CAS number

73384-59-5 (base)

InChI Key

VAAUVRVFOQPIGI-SPQHTLEESA-N

InChI

InChI=1S/C18H18N8O7S3/c1-25-18(22-12(28)13(29)23-25)36-4-6-3-34-15-9(14(30)26(15)10(6)16(31)32)21-11(27)8(24-33-2)7-5-35-17(19)20-7/h5,9,15H,3-4H2,1-2H3,(H2,19,20)(H,21,27)(H,23,29)(H,31,32)/b24-8-/t9-,15-/m1/s1

IUPAC Name

(6R,7R)-7-{[(2Z)-2-(2-amino-1,3-thiazol-4-yl)-2-(methoxyimino)acetyl]amino}-3-[(2-methyl-1,2,5,6-tetrahydro-1,2,4-triazin-3-yl)thio]methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid

SMILES

O=C2N1/C(=C(\CS[C@@H]1[C@@H]2NC(=O)C(=N\OC)/c3nc(sc3)N)CS\C4=N\C(=O)C(=O)NN4C)C(=O)O

6. References

DailyMed/FDA labels—adult PK (t½ 5.8–8.7 h, Vd 5.78–13.5 L, plasma/renal clearance; protein binding 95%→85%), distribution, pregnancy passage. DailyMed+2DailyMed+2
FDA/label safety—neonatal calcium–ceftriaxone precipitation and updated contraindication scope; warning context. FDA Access Data+2AAP Publications+2
WHOCC ATC/DDD Index—classification J01DD04 (ceftriaxone). FHI+1
PubChem—ceftriaxone base record (formula C₁₈H₁₈N₈O₇S₃, identifiers). PubChem
precisionFDA/GSRS—UNII 75J73V1629 and InChIKey VAAUVRVFOQPIGI-SPQHTLEESA-N. precisionFDA+1
Wikipedia (cross-checked identifiers; SMILES/InChI string; molar mass 554.57 g/mol). Wikipedia
Pfizer labeling—indications list for Ceftriaxone for Injection, USP. Pfizer Labeling

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