Ethambutol

Ethambutol (EMB, E) is a medication primarily used to treat tuberculosis.[3] It is usually given in combination with other tuberculosis medications, such as isoniazid, rifampicin and pyrazinamide.[4] It may also be used to treat Mycobacterium avium complex, and Mycobacterium kansasii.[3] It is taken by mouth.[3]

Ethambutol
Chemical structure of ethambutol (top) and photo of ethambutol crystals (bottom)
Clinical data
Trade namesMyambutol, Etibi,[1] Servambutol, others
Other names(2S,2’S)-2,2’-(Ethane-1,2-diyldiimino)dibutan-1-ol[2]
AHFS/Drugs.comMonograph
License data
Routes of
administration		by mouth
ATC code
Legal status
Legal status
  • In general: ℞ (Prescription only)
Pharmacokinetic data
Protein binding20–30%
Metabolismliver
Elimination half-life3–4 hours
Identifiers
CAS Number
PubChem CID
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.000.737
Chemical and physical data
FormulaC10H24N2O2
Molar mass204.314 g·mol−1
3D model (JSmol)
SMILES
  • CC[C@@H](CO)NCCN[C@@H](CC)CO
InChI
  • InChI=1S/C10H24N2O2/c1-3-9(7-13)11-5-6-12-10(4-2)8-14/h9-14H,3-8H2,1-2H3/t9-,10-/m0/s1 Y
  • Key:AEUTYOVWOVBAKS-UWVGGRQHSA-N

Common side effects include problems with vision, joint pain, nausea, headaches, and feeling tired.[3] Other side effects include liver problems and allergic reactions.[3] It is not recommended in people with optic neuritis, significant kidney problems, or under the age of five.[4] Use during pregnancy or breastfeeding has not been found to cause harm.[4][5] In the United States the FDA has raised concerns about eye issues in the baby if used during pregnancy.[3] Ethambutol is believed to work by interfering with the bacteria's metabolism.[3]

Ethambutol was discovered in 1961.[6] It is on the World Health Organization's List of Essential Medicines[7] and is available as a generic medication.[1]

Chirality and biological activity

(S,S)-(+)-Ethambutol is powerful and selective antitubercular drug. It is a typical example of an old drug that was introduced for clinical use in its unichiral form. Ethambutol contains two constitutionally symmetrical chiral centers in its structure and exists in three stereoisomeric forms. An enantiomeric pair (S,S)- and (R,R)-ethmabutol, along with the achiral stereoisomer called meso-form. The (S,S)-(+)-enantiomer harbors the antitubercular activity. This enantiomer is 500 and 12 fold more potent than the (R,R)-ethmabutol and the meso-form respectively. On the other hand, all the three isomers are equipotent in terms of the major side-effect of the drug, optic neuritis.[8] Toxicity is associated to both dose and duration of treatment. Hence the use of (S,S)-enantiomer greatly improved the risk/benefit balance.[9][10]

Medical uses

Ethambutol is used along with other medications to treat a number of infections including: tuberculosis, Mycobacterium avium complex, and Mycobacterium kansasii.[3]

Adverse effects

Mechanism of action

Ethambutol is bacteriostatic against actively growing TB bacilli. It works by obstructing the formation of cell wall. Mycolic acids attach to the 5'-hydroxyl groups of D-arabinose residues of arabinogalactan and form mycolyl-arabinogalactan-peptidoglycan complex in the cell wall. It disrupts arabinogalactan synthesis by inhibiting the enzyme arabinosyl transferase. Disruption of the arabinogalactan synthesis inhibits the formation of this complex and leads to increased permeability of the cell wall.

Pharmacokinetics

It is well absorbed from the gastrointestinal tract and well distributed in body tissues and fluids. 50% is excreted unchanged in urine.

See also

References
  1. Hamilton R (2015). Tarascon Pocket Pharmacopoeia (Deluxe Lab-Coat ed.). Jones & Bartlett Learning. p. 48. ISBN 9781284057560.
  2. "ethambutol (CHEBI:4877)". Chemical Entities of Biological Interest. UK: European Bioinformatics Institute. 18 August 2010. Main. Archived from the original on 19 July 2014. Retrieved 26 April 2012 – via ebi.ac.uk.
  3. "Ethambutol Hydrochloride". drugs.com. The American Society of Health-System Pharmacists. Archived from the original on 5 June 2016. Retrieved 10 December 2016.
  4. Stuart MC, Kouimtzi M, Hill SR, eds. (2009). WHO Model Formulary 2008. World Health Organization. pp. 136, 138, 588, 603. hdl:10665/44053. ISBN 9789241547659.
  5. "Prescribing medicines in pregnancy database". TGA.gov.au. Therapeutic Goods Administration, Department of Health, Australia. 3 March 2014. Archived from the original on 8 April 2014. Retrieved 22 April 2014.
  6. Landau R, Achilladelis B, Scriabine A (1999). Pharmaceutical Innovation: Revolutionizing Human Health. Chemical Heritage Foundation. p. 171. ISBN 9780941901215. Archived from the original on 2016-12-20.
  7. World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. 2019. hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
  8. Sheldon, Roger A. (1993). Chirotechnology : industrial synthesis of optically active compounds. New York: Marcel Dekker. ISBN 0-8247-9143-6. OCLC 27897833.
  9. Stereochemical aspects of drug action and disposition. S. K. Branch, Michel Eichelbaum, Bernard Testa, Andrew Somogyi. Berlin: Springer. 2003. ISBN 978-3-540-41593-0. OCLC 52515592.{{cite book}}: CS1 maint: others (link)
  10. Kannappan, Valliappan. "Ethambutol – Chiralpedia". Retrieved 2022-08-29.
  11. Lim SA (April 2006). "Ethambutol-associated optic neuropathy" (PDF). Annals of the Academy of Medicine, Singapore. 35 (4): 274–8. PMID 16710500. Archived (PDF) from the original on 2009-08-16.
  12. Lewis SM, Dirksen SR, Heitkemper MM, Bucher L, Harding M (5 December 2013). Medical-surgical nursing : assessment and management of clinical problems (9th ed.). St. Louis, Missouri. ISBN 978-0-323-10089-2. OCLC 228373703.
  13. Tripathi KD (August 2015). Essentials of Medical Pharmacology (Seventh ed.). India: Jaypee Brothers Medical Publishers. p. 769. ISBN 978-93-5025-937-5.
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