NTP Toxicology and Carcinogenesis Studies of l-Epinephrine Hydrochloride (CAS No. 55-31-2) in F344/N Rats and B6C3F1 Mice (Inhalation Studies).

l-Epinephrine, an endogenous neurotransmitter hormone, is widely used for the treatment of allergic and respiratory disorders. NTP Toxicology and Carcinogenesis studies of epinephrine hydrochloride were conducted by exposing groups of F344/N rats and B6C3F1 mice of each sex to an aerosol containing epinephrine hydrochloride for 14 days, 13 weeks, 15 months, or 2 years. During the 14-day and 13-week studies, control animals were exposed to dilute aerosols of hydrochloric acid (pH 2.8), whereas during the 15-month and 2-year studies, controls were exposed to aerosols of water. Genetic toxicology studies of epinephrine were conducted in Salmonella typhimurium and Chinese hamster ovary (CHO) cells. Fourteen-Day Studies: Rats and mice were exposed to 0 or 12.5-200 mg/m3 epinephrine hydrochloride. Deaths occurred in male rats exposed to 12.5 mg/m3 or more and in females exposed to 25 mg/m3 or more. Deaths of mice occurred at concentrations of 50 mg/m3 or higher. Compound-related clinical signs included an increased respiratory rate in all groups of epinephrine-exposed rats and mice. At higher concentrations (100 and 200 mg/m3), excessive lacrimation and dyspnea in rats and exaggerated visual and auditory reflexes in mice were observed. Thirteen-Week Studies: Rats and mice were exposed to 0 or 2.5-40 mg/m3 epinephrine hydrochloride. Deaths in rats and mice were not concentration related. Final mean body weights of chemically exposed and hydrochloric acid aerosol control rats and mice were generally similar. Increased respiratory rates were noted in rats and mice exposed to 40 mg/m3. Heart and adrenal gland weights of rats and mice and liver weights of mice exposed to 40 mg/m3 were greater than those of aerosol controls. Squamous metaplasia occurred in the respiratory epithelium of the nasal mucosa of rats and mice exposed to 40 mg/m3. Degenerative lesions of the laryngeal muscle were seen in male and female rats exposed to 20 or 40 mg/m3. Inflammation in the glandular stomach was seen in male and female mice exposed to 10, 20, and 40 mg/m3, and uterine atrophy was seen in 7/10 female mice exposed to 40 mg/m3. Two-year studies were conducted by exposing groups of 60 rats or each sex to 0, 1.5, or 5 mg/m3 epinephrine hydrochloride, 5 days per week for 103 weeks. Groups of 60 mice of each sex were exposed to 0, 1.5, or 3 mg/m3 epinephrine hydrochloride, 5 days per week for 104 weeks. Use of these exposure concentrations represented a departure from the usual practice of utilizing doses equivalent to one-half the maximum tolerated dose (MTD) and the MTD for 2-year carcinogenicity studies. Thus, although the dose levels exceeded maximum human therapeutic use levels (normalized to body weight and surface area), they were less than one-half the MTD. Fifteen-Month Studies: Results of hematologic analyses did not show compound-related changes. Absolute liver weights for exposed mice (3 mg/m3) and rats (5 mg/m3) and relative liver weights for exposed rats (5 mg/m3) were significantly lower than those for controls. The absolute kidney weights for mice exposed to 3 mg/m3 and the kidney weight to body weight ratio for male mice exposed to 3 mg/m3 were significantly lower than those for controls. No compound-related lesions were seen in rats or mice. Body Weights and Survival in the Two-Year Studies: Mean body weights and survival of exposed and control rats and mice were similar (survival, rats--male: control, 33/50; 1.5 mg/m3, 27/50; 5 mg/m3, 32/50; female: 32/50; 29/50; 30/50; mice--male: control, 33/50; 1.5 mg/m3, 34/50; 3 mg/m3, 36/50; female: 32/50; 35/50; 34/50). Nonneoplastic and Neoplastic Effects in the Two-Year Studies: Suppurative inflammation of the nasal mucosa, dilatation of the nasal glands (Bowman's and septal), and hyperplasia of the respiratory epithelium were seen at increased incidences in male rats exposed to 5 mg/m3 and in female rats exposed to 1.5 or 5 mg/m3. Hyaline degeneration of the olfactory epithelium in male mice and suppurative inflammation of the nasal passage and hyaline degeneration of the respiratory epithelium in female mice were increased in the 1.5 and 3 mg/m3 groups compared with controls. No neoplasms seen in these studies were considered related to chemical exposure. Genetic Toxicology: Salmonella gene mutation tests with l-epinephrine yielded negative results in strain TA100 in the presence of exogenous metabolic activation (S9) and equivocal results in the absence of S9. No mutagenic activity was observed in strains TA98, TA1535, or TA1537 with or without S9. The responses observed in the CHO cell assay for induction of sister chromatid exchanges were considered to be negative and equivocal in the presence and absence of S9 activation, respectively. l-Epinephrine did not induce chromosomal aberrations in CHO cells with or without S9. Conclusions: Under the conditions of these 2-year studies, no carcinogenic effects were observed in male or female F344/N rats exposed to aerosols containing 1.5 or 5 mg/m3 l-epinephrine hydrochloride for 2 years or in B6C3F1 mice exposed to 1.5 or 3 mg/m3 l-epinephrine hydrochloride for 2 years. However, these studies were considered to be inadequate studies of carcinogenic activity because the concentrations used, which were chosen to represent multiples of therapeutic doses, were considered too low for the animals to have received an adequate systemic challenge from the compound. Synonyms: adrenaline hydrochloride; 4-(1-hydroxy-2-(methylamino)ethyl)-1,2-benzenediol; (-)3,4-dihydroxy-a-((methylamino)methyl)benzyl alcohol hydrochloride; methylaminoethanol catechol hydrochloride Trade names for epinephrine formulations: Primatene®. Mist; Sus-Phrine®.; Epipen®.; Supravenin Hydrochloride®.; Bronkaid®.