Chemical formula: C₉H₁₃NO₃ Molecular mass: 183.204 g/mol PubChem compound: 5816
Adrenaline is a direct acting sympathomimetic agent, which exerts effects on both α and β adrenoceptors. It has more pronounced effects on β than on α adrenoceptors, although α effects prevail at high doses.
The effects of adrenaline include increased rate and force of cardiac contraction, cutaneous vasoconstriction and broncho-dilatation. With higher doses, stimulation of peripheral α receptors results in an increase in peripheral resistance and in blood pressure.
Through its action on alpha-adrenergic receptors, adrenaline lessens histamine induced vasodilation. Adrenaline also reduces the vascular permeability induced by histamine that occurs during anaphylaxis.
Adrenaline, through its action on beta-adrenergic receptors in bronchial smooth muscle, causes bronchial smooth muscle relaxation.
Adrenaline also alleviates pruritus, urticaria, and angioedema and may be effective in relieving gastrointestinal and genitourinary symptoms associated with anaphylaxis.
Pharmacologically active concentrations of adrenaline are not achieved following oral administration as it is rapidly oxidised and conjugated in the gastrointestinal mucosa and the liver. Absorption from subcutaneous tissue is slow due to local vasoconstriction; effects are produced within 5 minutes. Absorption is more rapid after intramuscular injection than after subcutaneous injection.
Adrenaline is rapidly distributed into the heart, spleen, several glandular tissues and adrenergic nerves. It readily crosses the placenta and is approximately 50% bound to plasma proteins.
Adrenaline is rapidly inactivated in the body, mostly in the liver by the enzymes catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO). Most of a dose of adrenaline is excreted as metabolites in urine.
After intravenous administration, the plasma half-life is about 2-3 minutes.
Following one nasal dose of nasal adrenaline 2 mg, the geometric mean plasma adrenaline concentration-time profile was overall within the range of that following one intramuscular dose of adrenaline injection 0.3 mg (using a needle-syringe product and an auto-injector product) 60 minutes post-dose. The integrated pharmacokinetic parameters of adrenaline are summarized in the following table.
Mean (CV%) and geometric mean plasma PK parameters following one or two doses of adrenaline (integrated analysis):
| Treatment | N | tmax (min) median (range) | Cmax (pg/mL) | AUClast (min*pg/mL) | ||
|---|---|---|---|---|---|---|
| Mean (%CV) | Geo.mean | Mean (%CV) | Geo.mean | |||
| Adrenaline 2 mg IN (HCP administration) | 78 | 20.5 (2 – 150) | 485 (70.6) | 361 | 40900 (67.5) | 32600 |
| Adrenaline 2 mg IN (self-administration) | 32 | 30 (10 – 240) | 448 (67.1) | 342 | 50365 (55.5) | 41077 |
| Adrenaline 2 mg IN (pediatrics) | 16 | 25.0 (2.5 – 120) | 540 (70.7) | 433 | 35500 (76.3) | 27800 |
| Adrenaline 2 mg twice (L/R) | 39 | 30 (6 – 150) | 1000 (93.1) | 706 | 86000 (77) | 66700 |
| Adrenaline 2 mg twice (R/R) | 39 | 30 (4 – 150) | 992 (75.3) | 729 | 86500 (60.5) | 69900 |
| Adrenaline 0.3 mg IM | 178 | 45 (3.9 -360) | 277 (65.4) | 234 | 27900 (38.7) | 26100 |
| Adrenaline 0.3 mg IM twice | 70 | 45 (6 – 180) | 436 (48.8) | 386 | 47500 (32.6) | 45300 |
| EpiPen 0.3 mg | 77 | 10 (2 – 45) | 581 (75.6) | 447 | 31600 (39.3) | 29200 |
| EpiPen 0.3 mg twice | 78 | 20 (4 – 360) | 754 (64.7) | 630 | 55000 (47.9) | 29200 |
IN: intranasal; IM: intramuscular
Adrenaline has a rapid onset of action after administration. Following nasal administration to healthy volunteers, adrenaline was rapidly absorbed after both single and repeat dosing, with a time to maximum plasma concentration in 20 to 30 minutes. In subjects with rhinitis (congestion and nasal oedema), adrenaline is absorbed more rapidly with the maximum concentration observed in about 10 minutes.
Adrenaline is rapidly inactivated in the body, mostly in the liver by the enzymes catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO).
Much of a dose of adrenaline is excreted as metabolites in urine. Elimination is mainly via metabolism of the liver and sympathetic nerve endings, with a small amount excreted unchanged in the urine. The plasma half-life following nasal administration is about 2 to 3 minutes.
In pediatric patients with Type I allergies weighing 30 kg or greater (age range: 8 to 17 years), following a single 2 mg nasal dose of nasal adrenaline, the geometric mean plasma adrenaline concentration time profile was similar to that of healthy adults receiving the same dose within about 15 minutes post-dose (in a different study) and then became slightly higher than that of healthy adults (see table).
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