Immune globulin subcutaneous, human - klhw 20% for primary humoral immunodeficiency: an open-label, Phase III study.

Aim: This prospective, Phase III study assessed the pharmacokinetics (PK), safety and tolerability of immune globulin subcutaneous, human - klhw 20% solution (IGSC-C 20%) in participants with primary humoral immunodeficiency (PI), compared with immune globulin injection (human), 10% caprylate/chromatography purified (IGIV-C 10%). Patients & methods: About 53 participants enrolled. Total 44 received IGIV-C 10% in the run-in phase and then entered the IV phase (with an additional nine who were already receiving IGIV-C 10% and entered the IV phase directly) for steady-state IV PK assessments. Total 49 entered the SC phase (weekly doses of IGSC-C 20% for ∼24 weeks). The PK profiles of IGIV-C 10% and IGSC-C 20% and their safety and tolerability parameters were compared. Results: At a dose adjustment factor of 1.37, IGSC-C 20% provided comparable (noninferior and bioequivalent) overall total immunoglobulin G exposure to IGIV-C 10% over an equal time interval. About 33 participants reported 79 adverse events during run-in + IV phases; 41 participants reported 141 adverse events during the SC phase, with most being local infusion site reactions. The majority of infusion site reactions were mild to moderate in severity. Conclusion: IGSC-C 20% was bioequivalent to IGIV-C 10% and was well tolerated, with a safety profile comparable with IGIV-C 10%, in this study. Trial registration: ClinicalTrials.gov identifier: NCT02604810.

Evaluation of the Safety, Tolerability, and Pharmacokinetics of Gammaplex® 10% Versus Gammaplex® 5% in Subjects with Primary Immunodeficiency.

PURPOSE: This phase 3, multicenter, open-label, randomized, two-period, crossover bioequivalence trial evaluated the safety, tolerability, and pharmacokinetics of intravenous immunoglobulins (IVIGs) Gammaplex 5% and Gammaplex 10% in 33 adults and 15 children with primary immunodeficiency diseases (PIDs). METHODS: Eligible adults received five Gammaplex 5% infusions followed by five Gammaplex 10% infusions, or vice versa, stratified by a 21- or 28-day dosing regimen. Pediatric subjects received five Gammaplex 10% infusions only. RESULTS: The primary objective, to demonstrate the bioequivalence of Gammaplex 10% and Gammaplex 5% at the 28-day dosing interval, was met based on the Gammaplex 10%/Gammaplex 5% ratio of area under the concentration versus time curve (AUC0-28) values. Throughout the study, total immunoglobulin G trough levels were well maintained, with total values generally ≥600 mg/dL (minimum level for study inclusion). At the dosing schedules and infusion rates used in this study, safety and tolerability were comparable and acceptable in adult and pediatric PID subjects treated with Gammaplex 10% and 5%. CONCLUSIONS: In this study, the first direct comparison of 5% IVIG and 10% IVIG products in PID subjects, the pharmacokinetic analysis demonstrated bioequivalence of Gammaplex 10% and Gammaplex 5% at the 28-day dosing interval. The Gammaplex 10% formulation was safe and well tolerated in pediatric and adult PID subjects. Based on the results from this bridging study in PID subjects, Gammaplex 10% could be expected to have a therapeutic effect similar to the licensed Gammaplex 5%, which has demonstrated efficacy and tolerability in patients with PID and idiopathic thrombocytopenic purpura.

Long-Term Tolerability, Safety, and Efficacy of Recombinant Human Hyaluronidase-Facilitated Subcutaneous Infusion of Human Immunoglobulin for Primary Immunodeficiency.

PURPOSE: Treatment of primary immunodeficiency diseases (PIDD) with subcutaneous (SC) infusions of IgG preceded by injection of recombinant human hyaluronidase (rHuPH20) (IGHy) to increase SC tissue permeability was evaluated in two consecutive, prospective, non-controlled, multi-center studies. METHODS: Subjects >4 years of age received SC IgG replacement at a weekly dose equivalent of 108 % of their previous intravenous (IV) dose, facilitated by prior injection of 75 U/g IgG of rHuPH20. Starting with weekly SC infusions, the interval was increased (ramped-up) to a 3- or 4-week schedule. RESULTS: Eighty-three subjects (24 < 18 years; 59 ≥ 18 years) received 2729 infusions (excluding ramp-up) at a mean dose of 0.155 g/kg/week in the pivotal and 0.156 g/kg/week in the extension study. IGHy exposure exceeded 30 months in 48 subjects. During 187.7 subject-years of IGHy exposure, 2005 adverse events (AEs) (10.68 per subject-year) occurred. The rate of related systemic AEs during consecutive 1-year periods remained low; the rate of related local AEs decreased from 3.68/subject-year in months 1-12 to approximately 1.50/subject-year after 30 months of treatment. Fifteen subjects transiently developed anti-rHuPH20 binding antibody. There was no difference in AE rates in these subjects before and after the first titer increase to ≥1:160. The rate of infections during IGHy exposure was 2.99 per subject-year and did not increase during the studies. Annual infection rates were 3.02 in subjects <18 years and 2.98 in subjects ≥18 years. CONCLUSIONS: Long-term replacement therapy with IGHy was safe and effective in 83 pediatric and adult subjects with PIDD.

Initiation of immunoglobulin therapy by subcutaneous administration in immunodeficiency patients naive to replacement therapy.

BACKGROUND: Patients with immunodeficiency diseases require lifelong treatment with immunoglobulin (Ig), yet few studies have vetted dosing strategies and effectiveness of Ig in older patient populations. Patients requiring subcutaneous (SC) Ig (SCIG) typically start with intravenous dosing before transitioning to SCIG weekly maintenance. In this retrospective review, we investigated an alternate strategy with higher initial SC doses among an older patient population with antibody deficiency syndromes. FINDINGS: Records of 13 patients (mean age, 70 years) with antibody deficiencies who were naive to treatment with Ig were assessed. SCIG (Vivaglobin® [Immune Globulin Subcutaneous (Human), 16% Liquid] or Hizentra® [Immune Globulin Subcutaneous (Human), 20% Liquid]) was given twice weekly (100 mg/kg) for 2 weeks, followed by weekly (100 mg/kg) administration The mean pretreatment IgG level was 460 mg/dL; at 1, 3, and 6 months after SCIG initiation, mean IgG serum levels were 852, 907, and 943 mg/dL, respectively. Maintenance doses were unchanged during 6 months of follow-up. All patients remain on SCIG (median, 44 months). One patient developed sepsis/cholangitis unrelated to treatment 3 months after starting SCIG; no other serious bacterial infections were reported. CONCLUSIONS: Initiation of SCIG by doubling the maintenance dose over 2 weeks may be a well-tolerated and effective option for patients with antibody deficiencies requiring Ig replacement, especially among older patients.

Recombinant human hyaluronidase-facilitated subcutaneous infusion of human immunoglobulins for primary immunodeficiency.

BACKGROUND: Subcutaneous immunoglobulin (IGSC) replacement therapy for primary immunodeficiency (PI) is equally efficacious to intravenous immunoglobulin (IGIV), induces fewer systemic reactions, and may be self-infused. Limited SC infusion volumes and reduced bioavailability, however, necessitate multiple infusion sites, more frequent treatment, and dose adjustment to achieve pharmacokinetic equivalence. Recombinant human hyaluronidase (rHuPH20) increases SC tissue permeability and facilitates dispersion and absorption, enabling administration of monthly doses in one site. OBJECTIVE: This study investigated the efficacy and tolerability of rHuPH20-facilitated IGSC (IGHy) in patients with PI. METHODS: In this open-label, multicenter phase III study, 87 patients with PI aged ≥2 years received 10% IGIV for 3 months, then IGHy (n = 83) for approximately 14 to 18 months at 108% of the IGIV dose. IGHy infusions began weekly, increasing to 3- or 4-week intervals. RESULTS: The majority (94.0%) of IGHy infusions were administered every 3 or 4 weeks, using one site (median, 1.09/month), with a mean volume of 292.2 mL. The bioavailability of IGHy measured by area under the concentration versus time curve was 93.3% of IGIV, which is pharmacokinetically equivalent. Systemic reactions were less frequent with IGHy than with IGIV (8.3% vs 25.0% of infusions). Local reactions to IGHy were generally mild to moderate, with a rate of 0.203 per infusion. The acute serious bacterial infection rate per subject-year for IGHy was low (0.025; upper 99% CI limit, 0.046). Overall infection rates per subject-year were 2.97 for IGHy and 4.51 for IGIV. CONCLUSION: IGHy was effective, safe, and pharmacokinetically equivalent to IGIV at the same administration intervals, but it caused fewer systemic reactions. Tolerability was good despite high infusion volumes and rates.

Safety and efficacy of home-based subcutaneous immunoglobulin G in elderly patients with primary immunodeficiency diseases.

BACKGROUND: Subcutaneous immunoglobulin (SCIG) is as effective as intravenous immunoglobulin (IVIG) in minimizing infections in patients with primary immunodeficiency diseases (PIDD) and is associated with fewer systemic adverse events (AEs). Self-infusion/home-based infusion of SCIG improves quality of life and may lower treatment costs compared with hospital or office-based IVIG therapy, but its suitability has not been assessed in elderly patients (≥ 65 years). METHODS: We conducted a retrospective chart review of 47 elderly patients with PIDD in a single clinical practice in the United States to evaluate the practicality, safety, and efficacy of home-based SCIG infusions in elderly patients with PIDD over a 13-month period. Measurements included baseline disease characteristics, previous and current immunoglobulin G (IgG) replacement regimens, self-administered versus assisted SCIG infusions, SCIG infusion parameters, serum IgG levels, infections, and AEs. RESULTS: Forty-seven of 111 elderly patients (42%) treated with IgG in this practice elected to receive SCIG. All 47 patients received SCIG infusions at home; 39 (83.0%) self-infused the medication. Most patients (n = 46; 98%) received weekly infusions, requiring a mean duration of 65.3 minutes. The mean SCIG dose of 103 mg/kg/week resulted in a mean steady-state serum IgG concentration of 1074 mg/dL. Two patients experienced serious infections on SCIG: an exacerbation of chronic obstructive pulmonary disease/bronchitis, and an abscess. There were no serious systemic AEs. Local injection site reactions, including swelling, redness, burning, or itching, were considered mild or moderate by the patients and resolved within 24 hours. No bruising, bleeding, or skin breakdown occurred, despite concomitant anticoagulant or platelet inhibitor treatment in 45% of patients. Two patients discontinued home-based SCIG, but did not continue any IgG treatment. No patient switched from SCIG to another route of IgG treatment. CONCLUSIONS: Home-based SCIG is safe and effective in elderly patients with PIDD, most of whom can self-infuse. Infection rates were low, and no AEs or difficulties in administering SCIG occurred that resulted in treatment discontinuation.

Pharmacokinetics of subcutaneous IgPro20 in patients with primary immunodeficiency.

BACKGROUND AND OBJECTIVES: Immunoglobulin replacement is a standard therapy for patients with primary immunodeficiencies. Subcutaneous administration of immunoglobulin offers more constant IgG levels than intravenous administration and simplifies administration for some patients. Use of L-proline as an excipient contributes to the stability of highly concentrated IgG preparations. The aims of the present study were to evaluate the pharmacokinetics of IgPro20 (Hizentra®), a new 20% subcutaneous IgG solution, and compare the area under the serum concentration-time curve (AUC) with that of a similar intravenous 10% IgG solution (IgPro10; Privigen®). At the request of the US FDA, an algorithm for determining IgG trough level ratios (TLRs) was developed in order to provide physicians with a practical tool for monitoring doses during steady-state IgPro20 therapy. METHODS: This was a prospective, open-label, multicentre, single-arm, phase III clinical trial conducted in the US. The study was performed in a primary-care setting. Eligible patients were males or females aged 6-75 years with a primary immunodeficiency (common variable immunodeficiency or X-linked agammaglobulinaemia) who had received regular treatment with IgPro10 for at least 3 months prior to entering this study and had achieved serum trough concentration (C(trough)) values ≥5 g/L. IgPro20 was administered subcutaneously once weekly at initial doses equivalent to 130% of patients' previous doses, based on the results obtained in a Vivaglobin® study and due to an FDA request. After run-in, each patient's dose was adjusted to achieve an AUC comparable to that achieved with IgPro10 administered intravenously. RESULTS: Eighteen patients completed the study. Mean IgPro20 : IgPro10 dose ratio (dose adjustment coefficient) was 1.53 (range 1.26-1.87). The resulting mean AUCs were 105.6 g · day/L for IgPro20 versus 103.2 g · day/L for IgPro10 (geometric mean ratio 1.002; lower one-sided 95% confidence limit [CL] 0.951). Thus, the primary endpoint of the study was met, as this result exceeded the pre-specified criterion of the lower one-sided 95% CL of ≥0.8 for non-inferiority. At these AUCs, which were considered equivalent, the mean IgPro20 : IgPro10 TLR, determined by the developed algorithm, was 1.29 (range 1.18-1.73). Titres of specific antibodies tested were well above respective product specifications, suggesting that protection against infection would be effective. CONCLUSION: Steady-state AUCs with subcutaneous IgPro20 and intravenous IgPro10 were equivalent. Mean dose adjustment coefficient and mean TLR can be used for initial dose conversion without risk of under-protection but vary too widely to be considered measures of equivalence. Trial registration number (clinicaltrials.gov): NCT00419341.

Efficacy, safety, and pharmacokinetics of a 10% liquid immune globulin preparation (GAMMAGARD LIQUID, 10%) administered subcutaneously in subjects with primary immunodeficiency disease.

A multi-center, prospective, open-label study was conducted in primary immunodeficiency disease patients to determine the tolerability and pharmacokinetics of a 10% liquid IgG preparation administered subcutaneously. Forty-nine subjects (3-77 years old) were enrolled. Pharmacokinetic equivalence of subcutaneous treatment was achieved at a median dose of 137% of the intravenous dose, with a mean trough IgG level of 1,202 mg/dL at the end of the assessment period. The overall infection rate during subcutaneous treatment was 4.1 per subject-year. Three acute serious bacterial infections were reported, resulting in a rate of 0.067 per subject-year. A low overall rate of temporally associated adverse events (8%), and a very low rate of infusion site adverse events (2.8%), was seen at volumes up to 30 mL/site and rates ≤ 30 mL/h/site. Thus, subcutaneous replacement therapy with a 10% IgG preparation proved effective, safe and well-tolerated in our study population of subjects with primary immunodeficiency disease.

New Frontiers in Subcutaneous Immunoglobulin Treatment.

Subcutaneous immunoglobulin (SCIG) treatment provides stable serum immunoglobulin G (IgG) levels, is associated with fewer systemic adverse events than intravenous immunoglobulin (IVIG) treatment, and offers the convenience of home therapy. In clinical practice, IVIG is still used preferentially for initiation of treatment in newly diagnosed patients with primary immunodeficiency (PI) and for immunomodulatory therapy, such as treatment of peripheral neuropathies, when high doses are believed to be necessary. The authors discuss recent experience in using SCIG in place of IVIG in these settings. SCIG has been successfully used for initiation of therapy in previously untreated PI patients. Seventeen of 18 PI patients achieved serum IgG levels ≥5 g/L after the loading phase. Daily treatment was well tolerated and provided opportunities for patient/parent training in self-infusion. SCIG has been used for maintenance therapy in multifocal motor neuropathy (MMN) in three recent clinical trials, with good efficacy and tolerability results. Seven of eight MMN patients maintained serum IgG levels of 14-22 g/L with a mean dose of 272 mg/kg/week, had stable muscle strength, and felt comfortable with self-administration. Four patients with polymyositis or dermatomyositis achieved improvement in serum creatine kinase levels and muscle strength with SCIG therapy. Recent experience with SCIG suggests that traditional concepts of immunoglobulin therapy may be challenged to increase available therapy options. SCIG can be used to achieve high IgG levels within several days in untreated PI patients and to maintain high serum levels, as shown in patients with MMN.

The new generation of liquid intravenous immunoglobulin formulations in patient care: a comparison of intravenous immunoglobulins.

Intravenous immunoglobulin (IGIV) replacement therapy is the standard of care for primary immunodeficiencies with impaired humoral immunity. It is also the immunomodulatory therapy of choice for some types of neuroimmunologic and autoimmune hematologic disorders and for immunomodulation in bone marrow and some solid organ transplants. Currently available IGIV products include older lyophilized formulations, 5% liquid products, and newer, liquid, ready-to-use, 10% formulations. Differences in the formulations, manufacturing processes, excipients, pH, and other physicochemical properties of IGIV products may affect their clinical efficacy and tolerability. Among at-risk patients, the possibility of serious complications such as renal insufficiency, heart failure, thrombotic events, and immunological reactions may be increased if an IGIV formulation has sugar as a stabilizer, has high sodium or immunoglobulin A (IgA) content, or is hyperosmolar. The 10% liquid formulations may offer advantages because of their lower IgA concentrations, optimal pH, glycine or proline stabilizers, low sodium content, and lower osmolality. Liquid formulations are more convenient for patients and health care providers due to shorter infusion times and easier preparation and administration.

Tolerability of a new 10% liquid immunoglobulin for intravenous use, Privigen, at different infusion rates.

PURPOSE: The tolerability of L-proline-stabilized Privigen, a new 10% liquid immunoglobulin for intravenous administration, was assessed at high infusion rates in a Phase III, open-label, single-arm, multicenter study in 45 patients with primary immune deficiencies. PATIENTS AND METHODS: Maximum infusion rates were not assigned prospectively. For analysis, patients were grouped according to maximum infusion rate in a low infusion rate group (8 mg/kg/min) and high infusion rate group (12 mg/kg/min). RESULTS: Twenty-three patients, selected at the investigators' discretion for the high infusion rate group based on their good tolerability, tolerated Privigen at 12 mg/kg/min with no increase in temporally associated adverse events (AEs) above the level they had experienced at 8 mg/kg/min. The proportion of infusions with temporally associated AEs in these patients was 0.079 [97.5% confidence interval (CI) 0.114] compared to 0.211 (97.5% CI 0.267) in the low infusion rate group. The most frequent AE was headache. Thus, selected patients tolerate Privigen at high infusion rates.

Pharmacokinetics of a new 10% intravenous immunoglobulin in patients receiving replacement therapy for primary immunodeficiency.

Intravenous immunoglobulin (IVIg) is used in treating immunodeficiencies and autoimmune or inflammatory disorders. As manufacturing processes and storage can alter IgG molecules, pharmacokinetic assessments are important for new preparations. Thus, we studied pharmacokinetics of IgPro10, a new 10% liquid IVIg product stabilised with l-proline, in patients with common variable immunodeficiency (CVID) and X-linked agammaglobulinaemia (XLA). Patients received IgPro10 for >or=4 months (median dose of 444mg/kg, at 3- or 4-week intervals). Median total IgG serum concentrations increased from 10.2g/l pre-infusion to 23.2g/l at infusion end. Serum IgG concentrations decreased in a biphasic manner; median terminal half-life was 36.6 days. Median half-lives were 33.2 for IgG(1), 36.3 for IgG(2), 25.9 for IgG(3) and 36.4 days for IgG(4). Specific antibody concentrations (anti-CMV, anti-Hemophilus influenzae type B, anti-tetanus toxoid and anti-Streptococcus pneumoniae) decreased with median half-lives of 22.3-30.5 days. IgPro10 pharmacokinetics were similar in patients with CVID and XLA, although patients with CVID showed higher levels of anti-tetanus and anti-S. pneumoniae antibodies than patients with XLA, suggesting residual specific antibody production. IgPro10 pharmacokinetics fulfilled expectations for and were similar to intact IgG products. Administration of IgPro10 at 3- or 4-week intervals achieved sufficient plasma concentrations of total IgG, IgG subclasses and antibodies specific to important pathogens.

Safety and efficacy of Privigen, a novel 10% liquid immunoglobulin preparation for intravenous use, in patients with primary immunodeficiencies.

PURPOSE: The present study was designed to evaluate the efficacy and safety of a novel, 10% liquid formulation of intravenous immunoglobulin, stabilized with 250 mmol/L L-proline (Privigen), in patients with primary immunodeficiency disease. MATERIALS AND METHODS: Eighty adults and children diagnosed with common variable immunodeficiency or X-linked agammaglobulinemia received intravenous Privigen infusions (200-888 mg/kg) at 3- or 4-week intervals over a 12-month period, according to their previously established maintenance dose. The primary endpoint was the annual rate of acute serious bacterial infections. RESULTS: There were six episodes of acute serious bacterial infections, corresponding to an annual rate of 0.08; the annual rate for all infections was 3.55. Mean serum IgG trough levels were between 8.84 and 10.27 g/L. A total of 1,038 infusions were administered, most of them at the maximum rate permitted (8.0 mg kg(-1) min(-1)). Temporally associated adverse events, possibly or probably related to study drug, occurred in 9% of infusions, either during or within 72 h after infusion end. CONCLUSION: Privigen is well tolerated and effective for the treatment of primary immunodeficiency.

Efficacy, safety and tolerability of a new 10% liquid intravenous immune globulin [IGIV 10%] in patients with primary immunodeficiency.

The present clinical study was designed to evaluate the efficacy, pharmacokinetics and safety of a new 10% liquid intravenous immune globulin in patients with primary immunodeficiency diseases. Sixty-one adults and children with primary immuno-deficiency diseases received doses of 300-600 mg/kg body weight every 21-28 days for 12 months. No validated acute serious bacterial infections were reported. The 95% confidence interval for the annualized rate of acute serious bacterial infections (primary endpoint) was 0-0.060. A total of four predefined validated other bacterial infections commonly occurring in primary immunodeficiency disease subjects were observed; none were serious, severe or resulted in hospitalization. The median elimination half-life of IgG was 35 days. Median total IgG trough levels varied from 9.6 to 11.2 g/L. Temporally associated adverse experiences were determined for 72 h after each infusion and the most common adverse experience was headache, which was associated with 6.9% of infusions. The study met the primary endpoint for efficacy and demonstrated excellent tolerability of the new 10% liquid intravenous imunoglobulin preparation.

Effects of esomeprazole 40 mg twice daily on asthma: a randomized placebo-controlled trial.

RATIONALE: Gastroesophageal reflux disease (GERD) is common in patients with asthma, suggesting an interaction between the two conditions. OBJECTIVES: To assess the effect of gastric acid suppression with the proton pump inhibitor esomeprazole on asthma outcomes in subjects with persistent moderate to severe asthma treated with antiinflammatory asthma medication. METHODS: In this double-blind study, subjects were randomized to receive esomeprazole 40 mg or placebo twice daily for 16 wk. According to nocturnal respiratory symptoms (NOC) and GERD, subjects were divided into three strata: GERD-/NOC+, GERD+/NOC-, and GERD+/NOC+. MEASUREMENTS AND MAIN RESULTS: A total of 770 subjects were randomized. There was no statistically significant improvement in morning peak expiratory flow (PEF) over placebo in the overall study population: 6.3 L/min (p = 0.061). Over the whole treatment period, in GERD+/NOC+ subjects (n = 350), esomeprazole provided an 8.7-L/min improvement (p = 0.03) in morning PEF, and a 10.2-L/min improvement (p = 0.012) in evening PEF over placebo. Among 307 subjects taking long-acting beta2-agonists, improvements over placebo were observed in morning PEF (12.2 L/min, p = 0.017) and in evening PEF (11.1 L/min, p = 0.024); these improvements were more pronounced in GERD+/NOC+ subjects. Esomeprazole 40 mg twice daily was well tolerated and no safety concerns were noted. CONCLUSIONS: Esomeprazole improved PEF in subjects with asthma who presented with both GERD and NOC. In subjects without both GERD and NOC, no improvement could be detected.

Clinical immunology in practice, new opportunities.

While research provides new opportunities for diagnosing and treating patients with allergic and immunological disorders, there are significant challenges to putting these advances into use in clinical practice. Each new test may require clinicians in private practice to battle with a health insurer's designated clinical laboratory in an effort to get this new test and other accurate immunological laboratory studies. A new test may or may not be covered by some health care plans and may or may not be available from their designated laboratories. Many of these laboratories send time-sensitive samples across the country with risk of time delays and poor specimen handling leading to inaccurate results and/or the need to send repeat specimens. The growing role of managed care in every medical decision has led to frustrations for the patient and physician. This frequently requires a consult at a tertiary care center, where laboratory studies may be more easily accessible with fewer restrictions. Where are the new opportunities? Some are found in the enhanced ability to make intelligent decisions in the diagnosis and treatment of immunological diseases. There is now a greater selection and availability of intravenous gamma-globulin (IVIG), that can be matched to individual patient needs. The appropriate selection of these products will decrease adverse reactions and increase safety. There was a major advance in the treatment of moderate and severe asthma with the addition of omalizumab therapy. It provides allergists and immunologists with their first monoclonal humanized anti-IgE antibody.

Possible mechanisms of influence of esophageal acid on airway hyperresponsiveness.

Airway hyperresponsiveness is among the defining phenomena in asthma. In this article, 3 mechanisms are reviewed to explain how gastroesophageal reflux (GER) may influence airway hyperresponsiveness. First, microaspiration may cause not only direct tissue injury, but may also trigger vagal reflexes. Second, acid infusion of the esophagus in a dog model and in humans has been shown to result in vagally mediated reflexes leading to bronchoconstriction. These reflexes have been studied using immunohistochemical techniques. Third, neuroinflammatory reflexes have been found to play a role in airway responses through the release of tachykinins, including substance P and neurokinin A. Combined, these 3 mechanisms may lead to an increase in vagal efferent impulses that can cause or augment airway hyperresponsiveness. Studies indicate that there is an increase in airway responsiveness in asthma patients who have documented GER. Further, based on the reported number of reflux episodes occurring during 24-hour pH monitoring, airway hyperresponsiveness to methacholine challenge tends to increase as GER worsens.