Racemic epinephrine

(RS)-epinephrine
Systematic (IUPAC) name
(R)-4-(1-hydroxy-
2-(methylamino)ethyl)benzene-1,2-diol
Clinical data
AHFS/Drugs.com epinephrine.html monograph
Pregnancy
category
  • AU: A
  • US: C (Risk not ruled out)
Routes of
administration		 IV, IM, endotracheal, IC
Legal status
Legal status
  • AU: S4 (Prescription only)
  • UK: POM (Prescription only)
  • US: ℞-only
Pharmacokinetic data
Bioavailability Nil (oral)
Metabolism adrenergic synapse (MAO and COMT)
Biological half-life 2 minutes
Excretion Urine
Identifiers
IUPHAR/BPS 509
ChemSpider 815 YesY
Chemical data
Formula C9H13NO3
Molar mass 183.204


Racemic epinephrine is a racemic mixture of epinephrine and is a sympathomimetic bronchodilator that is delivered by aerosol.[1] Commonly used in croup (laryngotracheobronchitis) and when stridor is present after removal of an endotracheal tube (extubation).[1][2] Racemic epinephrine prepared for aerosolization is equivalent to a 1:100 dose of epinephrine.

Overview

The term racemic epinephrine refers to a mixture of 50 % each of the dextro-rotatory and levo-rotatory isomers. The l-isomer [(R)-epinephrine] is present in the adrenal glands of animals and humans and is produced commercially by extraction from animal glands or by separation of the d- and l-isomers in the synthetic preparation. It is the epinephrine listed in the US Pharmacopoeia. The important difference in these isomers is in their physiological properties. The d-isomer [(S)-epinephrine] has about one fifteenth the pressor effect of the l-isomer, but has a more sustained action. Together the two isomers give a more prolonged result than the l-form—epinephrine USP—alone.[3] The racemic form has also been shown to be more stable under varying conditions of storage.[4] Studies have further demonstrated the racemic form gives better protection as an antihistaminic.[5][6][7]

Indications

Racemic epinephrine may be indicated when there is stridor present or when croup is suspected.[1][2] Nebulized and inhaled epinephrine (both racemic and levo(1)-epinephrine) has been shown to decrease hospitalization rates[8][9] in cases of bronchiolitis.

Contraindications

Racemic epinephrine should not be used in cases of epiglottitis or hypersensitivity to the drug.[1]

Side effects

Side effects include increased heart rate, nausea, anxiety, heart palpitations and headache.[1]

Mechanism of action

Racemic epinephrine works by stimulation of the α-adrenergic receptors in the airway with resultant tightening of the mucosa (mucosal vasoconstriction) and decreased fluid in the airway (subglottic edema) and by stimulation of the β-adrenergic receptors causing relaxation of the bronchial smooth muscle.[10][11]

Dosage

A common racemic epinephrine preparation for aerosolization is a 1:100 solution which equals 1 g/100mL or 10mg/mL.

Below, dosing is given using a less concentrated solution of 2.25% epinephrine which contains 2.25g/100mL or 2.25mg/mL.

Brand names

Common brand names include:

See also

References

  1. 1 2 3 4 5 6 7 Wiebe K, Rowe BH (2007). "Nebulized racemic epinephrine used in the treatment of severe asthmatic exacerbation: a case report and literature review.". CJEM 9 (4): 304–8. PMID 17626698.
  2. 1 2 3 Davies MW, Davis PG (2002). "Nebulized racemic epinephrine for extubation of newborn infants.". Cochrane Database Syst Rev (1): CD000506. doi:10.1002/14651858.CD000506. PMID 11869578.
  3. ↑ FEFFER JJ, MANN JP (April 1956). "Physiologic basis for rational therapy in chronic pulmonary emphysema". Postgraduate Medicine 19 (4): 332–40. PMID 13322728.
  4. ↑ MUNCH JC, SLOANE AB, LATVEN AR (October 1951). "Pressor drugs. II. Rate of loss in pressor potency of solutions of epinephrine and its analogs during storage". Journal of the American Pharmaceutical Association. American Pharmaceutical Association 40 (10): 526–9. doi:10.1002/jps.3030401015. PMID 14907450.
  5. ↑ Kunkel G, Steinijans VW, Borner K (1987). "Chrono-optimization of the time of evening administration with unequally divided twice-daily theophylline". Chronobiology International 4 (3): 359–68. doi:10.3109/07420528709083525. PMID 3315266.
  6. ↑ Coleridge J, Cameron P, Epstein J, Teichtahl H (August 1993). "Intravenous aminophylline confers no benefit in acute asthma treated with intravenous steroids and inhaled bronchodilators". Australian and New Zealand Journal of Medicine 23 (4): 348–54. doi:10.1111/j.1445-5994.1993.tb01434.x. PMID 8240146.
  7. ↑ Wolfe JD, Tashkin DP, Calvarese B, Simmons M (February 1978). "Bronchodilator effects of terbutaline and aminophylline alone and in combination in asthmatic patients". The New England Journal of Medicine 298 (7): 363–7. doi:10.1056/NEJM197802162980703. PMID 340945.
  8. ↑ Hartling L, Bialy LM, Vandermeer B, Tjosvold L, Johnson DW, Plint AC, et al. (2011). "Epinephrine for bronchiolitis.". Cochrane Database Syst Rev (6): CD003123. doi:10.1002/14651858.CD003123.pub3. PMID 21678340.
  9. ↑ Hartling, L; Fernandes, RM; Bialy, L; Milne, A; Johnson, D; Plint, A; Klassen, TP; Vandermeer, B (2011-04-06). "Steroids and bronchodilators for acute bronchiolitis in the first two years of life: systematic review and meta-analysis". BMJ (Clinical research ed.) 342: d1714. doi:10.1136/bmj.d1714. PMC 3071611. PMID 21471175.
  10. ↑ Cressman WR, Myer CM (1994). "Diagnosis and management of croup and epiglottitis.". Pediatr Clin North Am 41 (2): 265–76. PMID 8139876.
  11. ↑ Méndez-Samperio P, Palma-Barrios J, Vázquez-Hernández A, García-Martínez E (2004). "Secretion of interleukin-8 by human-derived cell lines infected with Mycobacterium bovis.". Mediators Inflamm 13 (1): 45–9. doi:10.1080/09629350410001664743. PMC 1781539. PMID 15203565.
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