Epinephrine absorption in children with a history of anaphylaxis

Fatal asthma or anaphylaxis?

The incidence of anaphylaxis is under-reported. Children with asthma are frequently atopic and prone to allergic reactions. Parents and clinicians may attribute wheeze of rapid onset to acute severe asthma, rather than recognising an anaphylactic event. Two cases of fatal anaphylaxis are reported who were initially diagnosed as acute severe asthma, and responded poorly to bronchodilator treatment. Survivors of "acute asphyxic asthma" should be screened for reactions to common allergens that provoke anaphylactic reactions. Even if no provoking factor is identified, the asthma management plan of children who survive an episode of acute asphyxic asthma should include intramuscular adrenaline (epinephrine) in addition to conventional bronchodilators.

Anaphylaxis: a review of causes and mechanisms

Anaphylaxis is a life-threatening syndrome resulting from the sudden release of mast cell- and basophil-derived mediators into the circulation. Foods and medications cause most anaphylaxis for which a cause can be identified, but virtually any agent capable of directly or indirectly activating mast cells or basophils can cause this syndrome. This review discusses the pathophysiologic mechanisms of anaphylaxis, its causes, and its treatment.

Food allergy

Food allergy encompasses a range of disorders that result from adverse immune responses to dietary antigens. This group of conditions includes acute, potentially fatal reactions, and a host of chronic diseases that mainly affect the skin and gastrointestinal tract. Tools for diagnosis and management have not changed much in the past two decades, and include the clinical history, physical examination, tests for specific IgE antibody to suspected foods, elimination diets, oral food challenges, and provision of medications such as epinephrine for emergency treatment. However, much research in the past few years has enhanced our understanding of the clinical, epidemiological, and immunological aspects of these disorders. In this review I will discuss these advances and incorporate them into an improved diagnostic and management scheme. Additionally, emergent diagnostic, treatment, and prevention strategies are reviewed.

Is epinephrine administration by sublingual tablet feasible for the first-aid treatment of anaphylaxis? A proof-of-concept study

PURPOSE

In order to explore the feasibility of sublingual administration of epinephrine tablets as a non-invasive first-aid treatment for anaphylaxis, we studied epinephrine absorption from this dosage form in an animal model.

METHODS

In a prospective, randomized, four-way crossover study, six rabbits received epinephrine 2.5 or 10 mg as a sublingual tablet, epinephrine 0.03 mg (0.3 ml) by intramuscular (IM) injection (positive control), and 0.9% NaCl (0.3 ml) IM (negative control). Pre- and post-dose blood samples were obtained for measurement of plasma epinephrine concentrations by HPLC-EC.

RESULTS

After administration of epinephrine 2.5 mg as a sublingual tablet, the mean (+/-SEM) C(max) was 2369+/-392 pg/ml, and the t(max) was 20.8+/-5.7 min. After administration of epinephrine 10 mg sublingually, the C(max) was 10836+/-2234 pg/ml, and the t(max) was 21.7+/-5.4 min. After IM epinephrine, the C(max) was 6445+/-4233 pg/ml, and the t(max) was 15.8+/-4.7 min. After IM 0.9% NaCl, the C(max) (endogenous epinephrine) was 518+/-142 pg/ml. The t(max) after both of the sublingual epinephrine tablet doses did not differ significantly from the t(max) after IM epinephrine, and the C(max) after the 10 mg sublingual epinephrine tablet dose did not differ significantly from the C(max) after IM epinephrine.

CONCLUSIONS

In this proof-of-concept study, administration of epinephrine as a sublingual tablet formulation resulted in rapid achievement of peak plasma epinephrine concentrations. Absorption studies in humans are needed.

DEFINITIONS

HPLC-high performance liquid chromatography; EC - electrochemical detection; C(max) - maximum plasma epinephrine concentration after dosing; t(max) - time of maximum plasma epinephrine concentration.

Preventing and managing drug-induced anaphylaxis

Drug-induced anaphylaxis and anaphylactoid reactions have increased in frequency with more widespread use of pharmaceutical agents. Anaphylaxis is a systemic, severe immediate hypersensitivity reaction caused by immunoglobulin (Ig) E-mediated immunological release of mediators of mast cells and basophils. An anaphylactoid reaction is an event similar to anaphylaxis but is not mediated by IgE. The incidence of anaphylactic or anaphylactoid reactions differs amongst classes of medications. Antibacterials are the most usual offenders, and penicillins are the most studied. Other compounds commonly causing reactions include non-steroidal anti-inflammatory drugs, anaesthetics, muscle relaxants, latex and radiocontrast media. Prevention, if possible, is the purpose of detailed patient history taking and physical examination. Simple strategies can be employed to decrease the risk of anaphylaxis. These include consideration of the route of drug administration, identification of patients with known causes of anaphylaxis, and the knowledge that certain medications cross react and are contraindicated in those with known history of anaphylaxis. Tests are available, and include IgE-specific skin tests and radioallergosorbent tests. Penicillins are the only compounds whose antigenic determinants are well documented, it is therefore difficult to determine the negative predictive value of other compounds tested. Oral challenge remains an alternative, though entails risk. Desensitisation procedures, as well as gradual dose escalation protocols, are available and can be implemented based on patient history and diagnostic testing. The management of anaphylaxis is based on control of the airway, breathing and circulation. Treatment consists of epinephrine (adrenaline) and supportive measures. Rapid diagnosis and intervention are important in these life-threatening reactions. After stabilisation, all individuals with a documented history of anaphylaxis require a Medic-Alert bracelet or necklace, and an identification card for their wallet or purse.

Role of epinephrine in acute stress

This article presents the likely pathway of stimuli generated by the recognition of high-intensity stressors to ultimately produce a fight-or-flight response. A key element is the recognition that psychological stressors that do not directly alter the internal environment represent the most important etiology of a fight-or-flight response. Adrenomedullary secretion is a critical component of that response; impromptu stimulation of the adrenal medulla can produce plasma epinephrine concentrations greater than 10,000 pg/mL. When these plasma levels reach the hypothalamus to act on the CNS, the result is facilitation of the decision making, and decision execution processes (fight-or-flight), and perhaps further sympathetic stimulation and vasopressin release. Subjects with underlying cardiovascular and/or metabolic pathology may be particularly susceptible to potentially lethal reactions to this neuroendocrine response. Additionally, since this biological reaction may be triggered by sudden changes in the social environment, the coordinated actions of epinephrine, sympathetic stimulation and vasopressin must be directed at not only optimizing the chances for survival, but also at attaining maximal preservation of the individual environmental and social domains.

EpiPen Jr versus EpiPen in young children weighing 15 to 30 kg at risk for anaphylaxis

BACKGROUND

The EpiPen Jr (0.15 mg) and EpiPen (0.3 mg) auto-injectors, widely prescribed for the out-of-hospital treatment of anaphylaxis, have not been compared prospectively in young children.

OBJECTIVE

The purpose of this investigation was to study the rate and extent of epinephrine absorption after use of the EpiPen Jr and the EpiPen in children weighing 15 to 30 kg.

METHODS

In a randomized, double-blinded, parallel-group pilot study, children at risk for anaphylaxis self-injected epinephrine using either an EpiPen Jr or an EpiPen with the aid of a physician. Plasma epinephrine concentrations, blood glucose, blood pressure, heart rate, and adverse effects were monitored before and for 180 minutes after the injection.

RESULTS

Children (age [mean +/- SEM], 5.4 +/- 0.4 years; weight [mean +/- SEM], 18.0 +/- 0.6 kg) who injected epinephrine with an EpiPen Jr achieved a maximum plasma concentration (mean +/- SEM) of 2037 +/- 541 pg/mL at 16 +/- 3 minutes. Children (6.6 +/- 0.5 years; 25.4 +/- 1.5 kg) who injected epinephrine with an EpiPen achieved a maximum plasma concentration of 2289 +/- 405 pg/mL at 15 +/- 3 minutes. Mean systolic blood pressure 30 minutes after epinephrine injection was significantly higher with the EpiPen than with the EpiPen Jr. After injection with the EpiPen Jr, every child experienced transient pallor; some also experienced tremor and anxiety. After injection with the EpiPen, every child developed transient pallor, tremor, anxiety, and palpitations or other cardiovascular effects; some also developed headache and nausea.

CONCLUSION

Epinephrine injection with the EpiPen rather than the EpiPen Jr raised the systolic blood pressure significantly but also caused more adverse effects. The beneficial pharmacologic effects and the adverse pharmacologic effects of epinephrine cannot be dissociated. For the out-of-hospital treatment of anaphylaxis, additional premeasured, fixed doses of epinephrine would facilitate more precise dosing in young children.

Epinephrine absorption in adults: intramuscular versus subcutaneous injection

We report a prospective, randomized, blinded, placebo-controlled, 6-way crossover study of intramuscular versus subcutaneous injection of epinephrine in young men. Peak plasma epinephrine concentrations were significantly higher (P < .01) after epinephrine was injected intramuscularly into the thigh than after epinephrine was injected intramuscularly or subcutaneously into the upper arm. We recommend intramuscular injection of epinephrine into the thigh as the preferred route and site of injection of this life-saving medication in the initial treatment of anaphylaxis.

Chronic idiopathic urticaria treatment

Chronic idiopathic urticaria (CIU) is a common skin condition that affects 0.1-3 % of people in the USA and Europe and accounts for nearly 75 % of all chronic urticaria cases. Up to 40 % of patients who have chronic urticaria for more than 6 months still have urticarial wheals 10 years later. The therapeutic management should first be oriented towards palliation of symptoms. A 2 % solution of ephedrine as a local spray is very useful for oropharyngeal edema. H1 antihistamines with a low potential for sedation are the most important first-line treatment. Combinations of various antihistamines may be useful in suppressing symptomatology. These include: a) First generation H1 antihistamines; b) Combinations of first and second generations using non-sedating agents in the morning and first generation drugs at night; c) Combinations of second generation antihistamines; d) Combination of doxepin with a first or second generation antihistamine; e) Combination of an H2 anti-receptor antihistamine (eg, cimetidine or ranitidine) with a first or second generation antihistamine. Preliminary reports suggest that desloratadine and anti-leukotrienes may be effective in treating some patients with chronic idiopathic urticaria.

Epinephrine dispensing for the out-of-hospital treatment of anaphylaxis in infants and children: a population-based study

BACKGROUND

Epinephrine is life-saving in the treatment of anaphylaxis. A limited number of fixed-dose epinephrine formulations are available for out-of-hospital treatment of this disorder.

OBJECTIVE

To examine dispensing patterns for epinephrine formulations over 4 consecutive years in a population of 279,638 infants, children, and adolescents (from birth up to but not including the 17th birthday).

METHODS

We used the Drug Programs Information Network, an administrative claims database for prescriptions dispensed in ambulatory care settings, developed from real-time computer links with retail pharmacies in the province of Manitoba, Canada. We studied the specific epinephrine formulation dispensed and the precise age of the infant or child at the time it was dispensed.

RESULTS

Epinephrine formulations were dispensed for 1.2% of the pediatric population (3,340 children). Boys comprised 59.5% of the recipients. Of all epinephrine formulations, 38.6% were dispensed as EpiPen Jr (0.15 mg), and 57.4% were dispensed as EpiPen (0.3 mg). EpiPen Jr was dispensed for patients ranging in age from 2 months to 16 years, 10 months, inclusive. EpiPen was dispensed for patients ranging in age from 1 year, 8 months to 16 years, 11 months, inclusive. During the 4 years studied, a subgroup of children transitioned from EpiPen Jr to EpiPen auto-injectors at a mean age of 6 years, 6 months +/- 2 years, 8 months (range 1 year, 10 months to 16 years, 11 months).

CONCLUSIONS

Both EpiPen Jr and EpiPen auto-injectors were dispensed over almost the entire age range of the pediatric population. Physicians should consider a child's age more carefully when prescribing these auto-injectors. Additional concentrations of epinephrine are needed in these fixed-dose formulations.

The US Peanut and Tree Nut Allergy Registry: characteristics of reactions in schools and day care

OBJECTIVE

Severe food-allergic reactions occur in schools, but the features have not been described.

STUDY DESIGN

Participants in the US Peanut and Tree Nut Allergy Registry (PAR) who indicated that their child experienced an allergic reaction in school or day care were randomly selected for a telephone interview conducted with a structured questionnaire.

RESULTS

Of 4586 participants in the PAR, 750 (16%) indicated a reaction in school or day care, and 100 subjects or parental surrogates described 124 reactions to peanut (115) or tree nuts (9); 64% of the reactions occurred in day care or preschool, and the remainder in elementary school or higher grades. Reactions were reported from ingestion (60%), skin contact/possible ingestion (24%), and inhalation/possible skin contact or ingestion (16%). In the majority of reactions caused by inhalation, concomitant ingestion/skin contact could not be ruled out. Various foods caused reactions by ingestion, but peanut butter craft projects were commonly responsible for the skin contact (44%) or inhalation (41%) reactions. For 90% of reactions, medications were given (86% antihistamines, 28% epinephrine). Epinephrine was given in school by teachers in 4 cases, nurses in 7, and parents or others in the remainder. Treatment delays were attributed to delayed recognition of reactions, calling parents, not following emergency plans, and an unsuccessful attempt to administer epinephrine.

CONCLUSIONS

School personnel must be educated to recognize and treat food-allergic reactions. Awareness must be increased to avoid accidental exposures, including exposure from peanut butter craft projects.

Diagnosis and management of childhood food allergy

The pediatrician plays a pivotal role in the initial diagnosis of food allergy. Alternative diagnoses are considered as a careful history, physical examination, and directed laboratory tests determine the type of adverse reaction and the responsible food. Through elimination diets in infants, appropriately selected tests for specific IgE, and, in some cases, supervised oral food challenges, a diagnosis is secured. Treatment consists of strict dietary elimination with provisions for emergency management of accidental ingestions. Referral to an allergist and dietitian is made as warranted by the severity and type of allergy and for follow-up for possible resolution of the allergy. The pediatrician also provides information to the family for the prevention of allergy in at-risk newborns. Future diagnostic tests and treatment modalities are likely to simplify the management of the food allergic child.

Diagnosis and management of food allergy

Food allergy affects 8% of children under 3 years of age and roughly 2% of the adult population. Major targets include cutaneous, gastrointestinal, and respiratory organs. Clinicians must recognize the spectrum of food allergy in order for these patients to be diagnosed accurately and managed. IgE-mediated reactions can progress rapidly, and severe reactions are often associated with refractory bronchoconstriction. IgE-mediated allergic patients should be equipped with education, an emergency action plan, and injectable epinephrine to aggressively treat food-induced reactions and prevent fatalities.

[Anaphylactic shock in the infant]

Anaphylactic shock is a life-threatening allergic reaction with cardiovascular collapse. The cardiovascular collapse may occur suddenly without warning signs or may be preceded by symptoms such as pruritus, wheezing, dyspnea, urticaria, pallor, digestive symptoms, and weakness. Food allergens, injected drugs and hymenoptera stings are the main etiologies. Anaphylactic shock requires an emergency treatment with immediate intramuscular or subcutaneous epinephrine injection. Subsequent avoidance of the inciting allergens is mandatory together with the availability of a first aid kit including ready-to-use epinephrine syringes. Besides its absolute necessity in any doctor's office, such first aid kits should be available in any children's group.

Can epinephrine inhalations be substituted for epinephrine injection in children at risk for systemic anaphylaxis?

BACKGROUND

For out-of-hospital treatment of anaphylaxis, inhalation of epinephrine from a pressurized metered-dose inhaler is sometimes recommended as a noninvasive, user-friendly alternative to an epinephrine injection.

OBJECTIVE

To determine the feasibility of administering an adequate epinephrine dose from a metered-dose inhaler in children at risk for anaphylaxis by assessing the rate and extent of epinephrine absorption after inhalation.

METHODS

We performed a prospective, randomized, observer-blind, placebo-controlled, parallel-group study in 19 asymptomatic children with a history of anaphylaxis. Based on the child's weight, 10, 15, or 20 carefully supervised epinephrine or placebo inhalations were attempted. Before dosing, and at intervals from 5 to 180 minutes after dosing, we monitored plasma epinephrine concentrations, blood glucose, heart rate, blood pressure, and adverse effects.

RESULTS

Eleven children (mean +/- standard error of the mean: 9 +/- 1 years and 33 +/- 3 kg) in the epinephrine group were able to inhale 11 +/- 2 (range: 3-20) puffs, equivalent to 74% +/- 7% of the precalculated dose or 0.078 +/- 0.009 mg/kg. They achieved a mean peak plasma epinephrine concentration of 1822 +/- 413 (range: 230-4518) pg/mL at 32.7 +/- 6.2 minutes. Eight children (10 +/- 1 years of age and 33 +/- 5 kg) in the placebo group were able to inhale 12 +/- 2 (range: 8-20) puffs, 89% +/- 3% of the precalculated dose, and had a peak endogenous plasma epinephrine concentration of 1316 +/- 247 (range: 522-2687) pg/mL at 44.4 +/- 16.7 minutes. In the children receiving epinephrine compared with those receiving placebo, mean plasma epinephrine concentrations were not significantly higher at any time, mean blood glucose concentrations were significantly higher from 10 to 30 minutes, mean heart rate was not significantly different at any time, and mean systolic and diastolic blood pressures were not significantly increased at most times. After the inhalations of epinephrine or placebo, the children complained of bad taste and many experienced cough or dizziness. After inhaling epinephrine, 1 child developed nausea, pallor, and muscle twitching.

CONCLUSIONS

Despite expert coaching, because of the number of epinephrine inhalations required and the bad taste of the inhalations, most children were unable to inhale sufficient epinephrine to increase their plasma epinephrine concentrations promptly and significantly. Therefore, we urge caution in recommending epinephrine inhalation as a substitute for epinephrine injection for out-of-hospital treatment of anaphylaxis symptoms in children.

[Anaphylaxis in children and adolescents: apropos of 44 patients aged 2 months to 15 years]

The increase in frequency of anaphylaxis, an acute allergic reaction which may be fatal, might be explained by the rise in food allergy. We report a cohort of 44 children, aged 2 months to 15.5 years, who were admitted in a pediatric emergency unit for serious allergic events. Thirty-two percent, 86% and 66% presented hypotension, severe edema and respiratory distress, respectively. Three patients were admitted to the ICU. One-fourth of all children had an angioneurotic edema history, 1/3 were asthmatics and 41% had known allergy. Etiologies were: food allergy (42.5%), drugs (14.8%), respiratory allergy (9%), miscellaneous (14.8%), idiopathic (6.4%) and unknown because of incomplete investigations (12.4%). Three-fourths of food allergies were comprised of the expected protein categories (milk, nuts, eggs and fish). Nine children had an allergic relapse during the following months. We otherwise assessed that adrenaline was underused by the medical staff.

Outdated EpiPen and EpiPen Jr autoinjectors: past their prime?

BACKGROUND

EpiPen and EpiPen Jr autoinjectors are often recommended for prehospital treatment of anaphylaxis. When these units become outdated, there may be a delay in replacing them.

OBJECTIVES

Our purpose was to evaluate unused, outdated EpiPen and EpiPen Jr autoinjectors, obtained from patients at risk for anaphylaxis, for epinephrine bioavailability and epinephrine content.

METHODS

We conducted a prospective, randomized, cross-over study of epinephrine bioavailability after injection from outdated autoinjectors in rabbits; controls included EpiPen and EpiPen Jr autoinjectors that had not expired ("in-date" autoinjectors) and intramuscular injection of 0.9% saline solution. In addition, the epinephrine content of the outdated EpiPen and EpiPen Jr autoinjectors was measured by a spectrophotometric method and an HPLC-UV method.

RESULTS

Twenty-eight EpiPen and 6EpiPen Jr autoinjectors were studied 1 to 90 months after the stated expiration date. Most were not discolored and did not contain precipitates. Epinephrine bioavailability from the outdated EpiPen autoinjectors was significantly reduced (P <.05) compared with epinephrine bioavailability from the in-date autoinjectors. The inverse correlation between the decreased epinephrine content of the outdated autoinjectors, assessed with an HPLC-UV method, and the number of months past the expiration date was 0.63.

CONCLUSIONS

For prehospital treatment of anaphylaxis, we recommend the use of EpiPen and EpiPen Jr autoinjectors that are not outdated. If, however, the only autoinjector available is an outdated one, it could be used as long as no discoloration or precipitates are apparent because the potential benefit of using it is greater than the potential risk of a suboptimal epinephrine dose or of no epinephrine treatment at all.

Use assessment of self-administered epinephrine among food-allergic children and pediatricians

BACKGROUND AND OBJECTIVES

Food allergy is a common cause of anaphylaxis, and early treatment with epinephrine can be life-saving. We sought to determine the ability of families with food allergic children and pediatricians to properly use self-injectable epinephrine.

METHODS

We enrolled families of consecutive, food-allergic pediatric patients newly referred to our allergy practice but previously prescribed epinephrine and a sampling of pediatricians. Parents or teenage patients answered a structured questionnaire concerning use of self-injectable epinephrine and demonstrated the use of devices with which they were familiar. Demonstrations were scored in a standard manner.

RESULTS

One hundred one families of food-allergic children (mean age of patients, 6.4 years) were enrolled. Self-injectable epinephrine was prescribed (mean of 2.7 years previously) primarily by pediatricians (n = 46) and allergists (n = 49). Patients were prescribed EpiPen (n = 93), EpiE-Z Pen (n = 11), and Ana-Kit (n = 3). Eighty-six percent of the families responded that they had the device with them "at all times," but only 71% of this group had epinephrine at the visit. Among those with the epinephrine, 10% had devices beyond the labeled expiration date. Thus, only 55% of the 101 families had unexpired epinephrine on-hand at the time of the survey. Among children in school, 77% had the medication available in school, and 81% stated that the school knew the indications for administration. Only 32% of the participants correctly demonstrated the use of the device. Twenty-nine attending pediatricians were enrolled (mean 14 yrs in practice; mean 4 epinephrine prescriptions/year). Familiarity with the devices was as follows: EpiPen (86%), EpiE-Z Pen (17%) and Ana-Kit (7%). Only 24% generally gave patients written materials concerning indications. Overall, 18% were familiar with and able to demonstrate correct use of at least 1 device (21% correctly demonstrated Epi-Pen). Seventeen pediatric residents were enrolled; 65% were familiar with the EpiPen; 36% demonstrated it correctly and only 1 resident was familiar with Ana-Kit.

CONCLUSIONS

Many parents of severely food-allergic children, and food-allergic teenagers cannot correctly administer their self-injectable epinephrine and may not have the medication readily available. Pediatricians are not familiar with these devices and may fail to review their use with patients. Improved patient and physician education is needed to ensure proper use of this life-saving medication.

Fish allergy: is cross-reactivity among fish species relevant? Double-blind placebo-controlled food challenge studies of fish allergic adults

BACKGROUND

Allergic reactions to fish are a common cause of food allergy in many areas of the world where fish is a major source of protein. Although different species of fish may be consumed, possible cross-reactivity has received limited investigation.

OBJECTIVE

The aim of this study was to assess potential cross-reactivity to different species of fish species using double-blind, placebo-controlled food challenges (DBPCFC) in fish-allergic adults and to compare skin test and RAST reactivity with the challenge response.

METHODS

Nine skin prick test and/or RAST-positive adult individuals with histories of an immediate-type reaction following fish ingestion were challenged with different fish species using double-blind, placebo-controlled food challenge.

RESULTS

Of a total of 19 double-blind, placebo-controlled fish challenges performed, 14 challenges (74%) resulted in the induction of objective signs that were consistent with an IgE-mediated response. The most common sign observed was emesis (37%); the most prevalent subjective symptoms reported were compatible with the oral allergy syndrome (84%). Three subjects reacted to at least three fish species and one subject reacted to two fish species tested. In regard to the positive challenges, predictive accuracy of skin prick test and RAST was 84% and 78%, respectively.

CONCLUSION

Our results indicate that clinically relevant cross-reactivity among various species of fish may exist. Advising fish-allergic subjects to avoid all fish species should be emphasized until a species can be proven safe to eat by provocative challenge.

Epinephrine absorption after different routes of administration in an animal model

BACKGROUND

The administration of epinephrine is the most important initial treatment in systemic anaphylaxis.

PURPOSE

We wanted to determine the relationship between the route of epinephrine administration and the rate and extent of epinephrine absorption.

METHODS

In a prospective, randomized, five-way crossover study in rabbits, we measured plasma epinephrine concentrations before, and at intervals up to 180 min after epinephrine administration by intramuscular or subcutaneous injection, or by inhalation, with intravenous epinephrine and intramuscular saline as the positive and negative controls, respectively.

RESULTS

Maximum plasma epinephrine concentrations were higher, and occurred more rapidly, after intramuscular injection than after subcutaneous injection or inhalation, and were 7719+/-3943 (S.E.M.) pg/mL at 32.5+/-6.6 min, 2692+/-863 pg/mL at 111.7+/-30.8 min and 1196+/-369 pg/mL at 45. 8+/-19.2 min, respectively. Intravenous injection of epinephrine resulted in a plasma concentration of 3544+/-422 pg/mL at 5 min, and an elimination half-life (t(1/2)) of 11.0+/-2.5 min. In the saline control study, the endogenous epinephrine concentration peaked at 518+/-142 pg/mL.

CONCLUSION

In this model, absorption of epinephrine was significantly faster after intramuscular injection than after subcutaneous injection or inhalation. The extent of absorption was satisfactory after both intramuscular and subcutaneous injections. Neither the rate nor the extent of absorption was satisfactory after administration by inhalation.