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`Preservatives in Nebulizer Solutions:
`
`
`
`Risks without Benefit
`
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`
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`Richard Beasley, M.D., David Fishwick, M.D.,Jon F Miles, M.D., and Leslie Hendeles, Pharm.D.
`
`
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`Edetate disodium (EDTA) and benzalkonium chloride (BAC) are often p:pesent
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`
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`as preservative or stabilizing agents in nebulizer solutions used to treat
`
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`asthma and chronic obstructive pulmonary disease. Benzalkonium chloride is
`
`
`
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`a potent bronchoconstrictor when inhaled in concentrations similar to those
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`
`Inclusion of BAC (together with
`
`in which it is present in these solutions.
`
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`
`
`EDTA) in the ipratropium bromide (Atrovent) nebulizer solution resulted in
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`paradoxic bronchoconstriction in some asthmatic patients and an overall
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`
`reduction in bronchodilator efficacy. The presence of BAC in albuterol
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`nebulizer solutions does not affect the short-term bronchodilator response to
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`
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`a single dose, although case reports suggest that its repeated use in patients
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`
`with severe asthma may result in paradoxic bronchoconstriction. When
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`inhaled by asthmatic subject s , EDTA also causes dose-dependent
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`bronchoconstriction, although it is less potent than BAC. T he lise of
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`preservative-free bronchodilator nebulizer solutions does not result in
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`clinically significant bacterial contamination if they are dispensed in sterile
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`unit-dose vials, in volumes and concentrations that do not require
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`modification by the user. Despite this evidence, in the United States a number
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`of solutions, including some preparations of albuterol, contain either BAC or
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`EDTA. Current regulations do not require that the concentration of
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`
`
`preservatives be documented on the product; however, considerably different
`
`
`
`
`doses of BAC are delivered with different products. For example, a standard
`
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`2.5-mg dose of albuterol nebulizer solution contains 50 µg of BAC when
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`
`
`administered from the multidose dropper bottle and 300 µg from the unit­
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`dose screw-cap product. Furthermore, it is legal for pharmacists to substitute
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`or compound solutions containing high concentrations of BAC when the
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`
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`physician has prescribed a preservative-free product. We recommend that the
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`
`
`United States follow the practice of most Western countries and withdraw
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`bronchodilator nebulizer solutions that contain preservatives such as BAC.
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`We further recommend that the solutions should be prepared under sterile
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`conditions, formulated preservative free, and made available in unit-dose vials.
`
`
`(Pharmacotherapy 1998;18(1): 130-139)
`
`OUTLINE
`
`Benzalkonium Chloride
`
`In Vitro Studies
`In Vivo Studies
`
`Clinical Relevance
`EDTA
`Department of Medicine, Wellington Sch ool of
`
`
`From the
`Medicine, Wellington, New Zealand (Dr s. Beasley,
`In Vivo Studies
`
`Fishwick, and Miles); and the C ollege of P harmacy and
`
`Clinical Relevance
`
`
`
`
`Pediatric Pulmonary Division, University of Florida Health
`
`Bacterial Contamination
`
`
`
`Science Center, Gainesville, Florida (Dr. Hendeles).
`The United States
`This review is based on a report that was p repared for
`Summary
`
`
`and funded by Dey Laboratories Inc., Napa, California.
`
`
`Add re s s reprint requests to Richard Beasley, M,D.,
`Nebulization is a common method of adminis­
`
`
`
`Departme nt of Medicine, Wellington School of Medicine,
`
`
`
`
`tering pharmacologic agents in the treatment of a
`
`
`P.O. Box 7343, Wellington South, New Zealand.
`
`Liquidia's Exhibit 1070
`Page 1
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`

`

`131
`
`In Vitro Studies
`Benzalkonium chloride has complex activities
`against rat serosal mast cells in vitro.I4 In
`concentrations between 1 and 3 pg/ml it inhibits
`histamine release induced by polyamines such as
`48/80, bradykinin, and substance P, but not that
`caused by antigens, ionophores, monoamines,
`and detergents. However, at concentrations
`greater than 5 pg/ml BAC causes histamine
`release itself, releasing in excess of 90% of the
`histamine content at a concentration of 30 pg/ml.
`This concentration is equivalent to the minimum
`recommended (25 pg/ml) for the use of BAC as a
`di~infectant,’~ suggesting that the effect could be
`related to the surfactant properties of the
`hydrophobic and cationic groups of the
`molecule. This mechanism is also consistent
`with the observation that heat inactivation of the
`mast cells does not prevent the histamine
`re1ea~e.l~ Further work in rat serosal mast cells
`showed that BAC in a concentration of 1.0 pg/ml
`may enhance IgE-dependent release of the
`preformed mediator 5-hydroxytryptamine. l6
`
`PRESERVATIVES IN NEBULIZER SOLUTIONS Beasley et al
`number of different respiratory disorders
`including asthma, chronic obstructive pulmonary
`disease (COPD), cystic fibrosis, lung (hyaline
`membrane) disease of immaturity, and immuno-
`deficiency disorders. In particular, it has gained
`widespread use in the treatment of asthma and
`COPD, as it allows high doses of broncho-
`dilators to be delivered to the lungs despite the
`presence of airflow obstruction. Although the
`efficacy of bronchodilator nebulizer therapy was
`established soon after its introduction, it was not
`long before reports began to appear of paradoxic
`bronchoconstriction associated with it.’,
`Factors associated with this response include
`o~molality,~~ a~idity,~. and chemical additives
`such as preservatives’~ and stabilizers’ in the
`solution. In addition, formation of a weak p-blocking
`metabolite from isoproterenol was rep~rted.~
`The potential for chemical additives to cause
`paradoxic bronchoconstriction was first
`recognized with an isoproterenol nebulizer
`solution that contained sodium metabisulfite.’,
`When administered to asthmatic patients the
`solution had the potential to worsen the degree
`of airflow obstruction as a consequence of sulfur
`dioxide (SOz) released from metabisulfite. Sulfur
`dioxide levels ranging from between 0.1 and 6.0
`parts per million (pprn) were measured in
`nebulizer solutions commercially available for
`bronchodilator
`The clinical significance
`of these levels is suggested by the fact that
`sensitive asthmatics may experience broncho-
`spasm while exercising when inhaling as little as
`0.1 ppm SOz,” and even nonasthmatics may
`develop bronchospasm at a level of 6 ppm.13
`These findings led to the removal of sulfites from
`most (although not all) commercially available
`nebulizer solutions.
`
`In Vivo Studies
`Initial experiments on the airway effects of
`inhaled BAC involved six asthmatic subjects who
`developed paradoxic bronchoconstriction after
`inhaling a bronchodilator (Atrovent) nebulizer
`solution containing BAC.7 Inhalation of
`increasing concentrations of BAC 0.125-5.0
`mg/ml produced dose - dep e nde n t bronc h o -
`constriction that persisted for longer than 60
`minutes. The cumulative geometric mean
`concentration of BAC provoking a 20% fall in
`forced expiratory volume in 1 second (PC2oFEV1)
`was 0.30 mg/ml (range 0.13-2.0 mg/ml).
`In a study of patients with mild atopic asthma
`who were not selected on the basis of a history of
`paradoxic bronchoconstriction with nebulizer
`solutions, inhalation of increasing concentrations
`of BAC nebulizer solution caused concentration-
`related falls in FEVl in all 12 ~ubjects.’~ The
`geometric mean PCzoFEVl for BAC was 4.0
`mg/ml (range 0.9-24.0 mg/ml), compared with
`0.6 mg/ml for histamine (range 0.1-3.9 mg/ml).
`The slopes of the concentration-response curves
`with BAC and histamine did not significantly
`depart from parallel. Based on these results it
`could be estimated that histamine was about 7.4
`times more potent as a bronchoconstrictor
`agonist than BAC on a mass basis.
`In a similar group of nine subjects with mild
`atopic asthma,” the geometric mean PCzoFEVl
`
`Benzalkonium Chloride
`The preservative most commonly present in
`nebulizer solutions was benzalkonium chloride
`(BAC), a mixture of quaternary benzyldimethyl-
`alkylammonium chlorides. It was added for its
`bactericidal properties and until recently was an
`ingredient in a number of commercially available
`nebulizer solutions including albuterol, fenoterol,
`metaproterenol (orciprenaline) , beclomethasone
`dipropionate, and ipratropium bromide. However,
`this use was not preceded by safety studies
`examining its effects when inhaled by asthmatics,
`and ignored in vitro studies that suggested that it
`would have the potential to cause an adverse
`airways response.
`
`Liquidia's Exhibit 1070
`Page 2
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`

`

`132
`
`PHARMACOTHERAPY Volume 18, Number 1,1998
`
`for BAC was 5.0 mg/ml (range 0.5-19.5 mg/ml).
`This response was reproducible, with a repeat
`dose-response challenge in the same subjects
`resulting in a mean PCloFEVl of 2.8 mg/ml
`(range 0.4-15.6 mg/ml). Patients most sensitive
`to the bronchoconstrictor effects of BAC were
`those with severe asthma, as determined by
`marked bronchial hyperresponsiveness.
`The relationship between airway sensitivity to
`inhaled BAC and predisposition to airway
`hyperresponsiveness was investigated in adults
`with asthma.” Of the 28 subjects, 17 (61%)
`developed marked bronchoconstriction with
`inhalation of BAC, and their recovery was
`slow. The amount of BAC that caused broncho-
`constriction was about 300 pg, similar to that
`contained in a 2.5-mg dose of albuterol nebulizer
`solution from the screw-cap product currently
`available in the United States. Inhalation of BAC
`also enhanced the response to inhaled histamine
`delivered 1 hour later. The clinical implication of
`this observation was that inhalation of BAC could
`temporarily enhance nonspecific bronchial
`reactivity, thereby making an asthmatic patient
`more susceptible to developing broncho-
`constriction in response to provoking stimuli.
`In these studies, the inhibitory effects of potent
`pharmacologic agents provided evidence that
`BAC-induced bronchoconstriction results from a
`combination of mast cell activation and stimu-
`lation of peripheral and central neural pathways.
`
`Clinical Relevance
`The possibility that BAC in nebulizer solutions
`may lead to either reduced bronchodilator
`
`efficacy or paradoxic bronchoconstriction was
`investigated in a series of studies and case reports
`of ipratropium bromide and albuterol nebulizer
`solutions.
`
`lpratropium Bromide
`There is strong evidence that BAC in
`commercially available Atrovent nebulizer
`solution influences airways response. A series of
`studies identified that inhalation of Atrovent
`containing both BAC 0.25 mg/ml and edetate
`disodium (EDTA) 0.5 mg/ml by asthmatic
`subjects may cause marked bronchoconstriction,
`and that their exclusion results in a significantly
`greater bronchodilator effect.7, 2o For example, in
`an unselected group of 22 adults with stable
`
`a ~ t h m a , ~ six subjects developed broncho-
`constriction after inhaling 4 ml (1.0 mg>’ of
`Atrovent, with a mean fall in FEVl of 35% at 2
`minutes after inhalation (Figure 1). When the
`six subjects inhaled 4 ml (1.0 mg) preservative-
`free ipratropium bromide sblution, all showed
`appropriate bronchodilation, with the mean FEVl
`increasing to 12% from baseline at 2 minutes.
`A double-blind, randomized clinical trial in 30
`adult asthmatics documented a fall in FEVl
`greater than 20% of baseline in 5 patients (17%)
`receiving the preservative-containing Atrovent,
`but none in those receiving 2 ml (0.5 mg) of the
`preservative-free ipratropium bromide solution.20
`Inhalation of preservative-free solution resulted
`in more rapid and greater overall bronchodilation
`than inhalation of Atrovent (Figure 2). It is
`likely that BAC was responsible for the
`bronchoconstriction associated with Atrovent, as
`the concentration (0.25 mg/ml) was within the
`range that causes bronchoconstriction when
`inhaled by asthmatic subjects, in contrast to
`EDTA (0.5 mg/ml), which is about one-tenth as
`
`0 I 6
`
`10
`
`16
`
`50
`Tim Iminl
`Figure 1. Changes in airway caliber after inhalation of
`nebulised Atrovent (A), preservative-free ipratropium
`bromide (0) and saline (m) in the six asthmatic subjects in
`whom the FEVl fell more than 20% after inhalation of 4-ml
`solution of nebulized Atrovent. Each point represents the
`mean FEVl expressed as percentage of baseline, and each
`bar the SEM. From reference 7.
`
`n
`
`i
`*)
`
`Q
`M
`15
`time (min)
`Figure 2. Effect of Atrovent (m) and preservative-free
`ipratropium bromide (A) on airway caliber in 30 subjects.
`Each point represents the mean FEVl expressed as
`percentage of baseline, and each bar the SEM. From
`reference 20.
`
`Liquidia's Exhibit 1070
`Page 3
`
`

`

`PRESERVATIVES IN NEBULIZER SOLUTIONS Beasley et al
`
`133
`
`potent as a bronchoconstrictor agent.
`In a similar study in children with mild asthma,
`1 ml of ipratropium bromide nebulizer solution
`containing BAC and EDTA resulted in a small,
`insignificant reduction in bronchodilation,
`compared with the preservative-free solution.2'
`This finding is not inconsistent with adult studies
`in which higher doses of preservatives were
`administered to patients with more severe asthma,
`as the bronchoconstrictor response to both BAC
`and EDTA is dose dependent, and in the case of
`BAC, is greater in subjects with markedly increased
`bronchial hyperresponsiveness.
`
`Albuterol
`Only one controlled study has examined the
`effect of BAC (concentration 0.1 mg/ml) on the
`bronchodilator response resulting from a single
`dose of albuterol nebulizer solution.22 Twenty-
`two patients with moderately severe asthma
`(baseline predicted FEVl 43-91%) came to the
`laboratory on two occasions to inhale 2.5 ml
`albuterol nebulizer solution (albuterol 1 .O
`mg/ml) with or without BAC 0.1 mg/ml according
`to a double-blind protocol. Paradoxic broncho-
`constriction, defined as a fall in FEVl greater
`than 5% of baseline, did not occur in any subject
`after either treatment. There was no significant
`difference in airways response between the
`solutions. Possible reasons for this difference in
`effect of BAC in albuterol or ipratropium bromide
`solution include its lower concentration in the
`albuterol solution (0.1 vs 0.25 mg/ml), absence
`of EDTA in the albuterol solution, and greater
`potency and more rapid onset of bronchodilator
`action of albuterol.
`This study is relevant to the administration of
`single doses of albuterol nebulizer solution only,
`rather than repeat administration, which would
`occur in the treatment of a severe asthma attack.
`International consensus guidelines23 recommend
`that albuterol be administered initially at a
`dosage of 2.5-5.0 mg every 20 minutes and then
`hourly, or even continuous nebulization, in the
`treatment of severe asthma in a hospital-based
`emergency department. To our knowledge no
`studies have examined the effects of BAC in
`albuterol nebulizer solution when administered
`repeatedly in high doses in severe asthma.
`However, at least two case reports in the
`literature provide evidence for an association
`between repeated use of albuterol nebulizer
`solution containing BAC and the occurrence of
`paradoxic bronchoconstriction.
`
`Patient No. 1. A 64-year-old man experienced a
`respiratory arrest after nebulization with
`albuterol and ipratropium bromide solutions
`containing BAC in concentrations of 0.1 and 0.25
`It is possible that the
`mg/ml, re~pectively.~~
`ipratropium bromide solution also contained
`EDTA, but this was not stated. The patient, who
`had severe chronic obstructive airway disease,
`complained of increased breathlessness after each
`nebulized treatment with albuterol 1 ml mixed in
`ipratropium bromide 2 ml. The deterioration
`was confirmed with lung function measurements,
`with for example, pretreatment FEVl falling from
`0.58 to 0.49 L 30 minutes after treatment. The
`patient suffered a respiratory arrest 30 minutes
`after nebulizer therapy. This was attributed to
`the effect of BAC in the solutions in view of the
`time course, the amount of BAC present in the
`solutions, and the lack of this reaction to drugs
`when administered by metered-dose inhalation.
`The authors calculated that the patient was
`exposed to a dose of 0.6 mg of BAUtreatment,
`compared with doses of less than 0.2 mg shown
`to drop FEVl by 20% of baseline in asthmatic
` patient^.^. l9
`Patient No. 2. A 16-month-old girl was admitted
`to intensive care with severe respiratory distress
`and given albuterol containing BAC by
`nebulization every 30 minutes and then
`By 12 hours after admission her condition began
`to deteriorate, and while preparations were made
`for intubation and ventilation, she was
`administered preservative-free terbutaline 3 mg
`with a favorable response. When albuterol
`nebulizer solution was administered again, it
`again resulted in significant deterioration with
`documentation of a drop in arterial oxygen
`saturation. Again, a single treatment with
`terbutaline by inhalation resulted in complete
`clearing. The authors concluded that the
`paradoxic bronchoconstriction was highly
`suggestive of an adverse reaction to BAC in the
`albuterol nebulizer solution. It was evident from
`this report that it would be difficult to recognize
`deterioration due to a bronchodilator nebulizer
`solution in such circumstances, as lack of
`response to a high-dose bronchodilator is one of
`the characteristic features of life-threatening
`asthma.
`Complementing this second case report are
`two recent studies in infants with asthma
`showing that paradoxic bronchoconstriction after
`albuterol nebulizer solution containing BAC is
`not uncommon.26. 27 In both studies, adminis-
`
`Liquidia's Exhibit 1070
`Page 4
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`

`

`134
`
`PHARMACOTHERAPY Volume 18, Number 1, 1998
`
`tration of nebulized albuterol solution containing
`BAC caused acute deterioration in lung function.
`Although the authors raised a number of
`possibilities to account for the deterioration,
`including changes in osmolality during the
`process of nebulization and a reduction in airway
`smooth muscle tone leading to a change in
`airway compliance, the potential adverse effects
`of BAC were not excluded.
`Thus the available evidence suggests that
`although the presence of BAC in an albuterol
`nebulizer solution is unlikely to affect the
`bronchodilator response after a single dose, it
`may cause paradoxic bronchoconstriction with
`repeat administration in patients with severe
`asthma, a response that would be difficult to
`detect clinically. Clinical studies are urgently
`required to resolve this issue.
`
`Sensitization
`In addition to short-term adverse airway
`effects of BAC, the possibility also exists that
`sensitization to this agent may occur with
`repeated exposure. The initial report of possible
`sensitization to BAC came from a study of 113
`workers in the pharmaceutical cosmetic industry
`with occupational exposure to quaternary
`ammonium salts such as BAC.28 Among these
`workers, 17 had positive skin patch tests; 10 of
`the 17 developed eczema, conjunctivitis, or
`rhinitis. Although no cases of occupational
`asthma were reported, a case of presumed
`occupational asthma due to BAC was described
`by others.
`Patient No. 1. A 37-year-old nonsmoker initially
`developed a dry cough and rhinorrhea, then
`experienced her first attack of asthma about 4
`months after starting work in a hospital
`laundry2' At first, because of the suspected role
`of trichloroethylene used in the dry-cleaning
`process, she was transferred to the wards as an
`aide, but her asthma did not regress. Both in the
`laundry and in the ward, the patient used
`disinfectant products based on BAC for cleaning
`floors. Her condition worsened, and results of
`investigations included positive patch tests to
`BAC at 4 hours and a positive bronchial
`provocation test to the agent. In the latter test,
`inhalation of BAC in a concentration of 100
`mg/ml led to a maximum 35% fall in peak
`expiratory flow rate (PEFR) after 15 minutes.
`This airways response was prolonged, as despite
`initial reversal with 200 mg albuterol, the PEFR
`again fell by 26% after 3 hours. In contrast,
`
`bronchial provocation with trichloroethylene did
`not cause a significant airway response; also skin
`patch tests to this and other agents were negative.
`A diagnosis of occupational asthma due to BAC
`was made, although the airway response to BAC
`may have reflected the degree of the patient's
`bronchial hyperresponsiveness, rather than
`specific sensitization to BAC.
`
`I
`
`Anaphylactoid Reaction
`Anaphylactic reaction, including marked
`flushing, dizziness, cough, and itching of the face
`and neck, occurred after treatment with albuterol
`nebulizer solution including BAC in a concen-
`tration of 0.1 mg/ml.30 Investigations indicated
`that this response was due to BAC in the
`solution. Indeed,the patient experienced a more
`severe systemic reaction with angioedema after
`intradermal testing with BAC.
`
`EDTA
`Edetic acid is a calcium-chelating agent that
`does not inhibit microbial growth. It is present
`in some nebulizer solutions to chelate metallic
`ions and thus prevent solution discoloration. As
`with BAC, its presence in commercially available
`nebulizer solutions was not based on research
`investigating its safety.
`
`In Vivo Studies
`Animal Models
`In anesthetized Basenji-Greyhound (BG) dogs
`with hyperreactive airways, a 5-minute challenge
`with aerosols of EDTA resulted in greater than 4-
`fold increase in pulmonary resistance and 2-fold
`reduction in dynamic ~ompliance.~~ Peak response
`occurred after 5 minutes, with continued effect
`persisting for at least 25 minutes. Although less
`marked in comparison, airway constriction was
`also induced by EDTA in pure-bred Basenji dogs
`that lack airway hyperresponsi~eness.~~
`These studies showed that the airway effect of
`EDTA is due to calcium chelation and not to
`either the acidity or osmolality of solution.
`Although the precise mechanisms by which
`calcium chelation induces bronchoconstriction in
`BG dogs is unclear, it may involve mediator
`release, since citric acid-induced broncho-
`constriction is blocked by FPL 55712,33 is
`
`attenuated by sodium c r ~ m o g l y c a t e , ~ ~ and is
`associated with probable release into the plasma
`of LTD+33, 34 Vagally mediated reflexes are not
`involved, since atropine is ineffective in
`
`Liquidia's Exhibit 1070
`Page 5
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`

`

`PRESERVATIVES IN NEBULIZER SOLUTIONS Beasley et al
`
`135
`
`preventing the bronchoconstrictor response to
`either citric acid or EDTA.31, 3 2 , 35 In further
`experiments by this group, EDTA-induced
`bronchoconstriction was significantly attenuated
`by albuter01.~~
`
`Asthmatic Subjects
`The airways effects of EDTA in asthmatic
`subjects were investigated in only one study; the
`original investigation of the bronchoconstrictor
`properties of preservatives in Atrovent (Table l).7
`Six of 22 subjects who developed a 20% or
`greater fall in FEVl after Atrovent nebulizer
`solution containing both BAC and EDTA came to
`the laboratory on two occasions to inhale double-
`blind 4-ml (1-mg) solutions of increasing
`concentrations of nebulized EDTA 0.25-10.0
`mg/ml or BAC 0.125-5.0 mg/ml until the FEVl
`fell by more than 20%. As with BAC, inhalation
`of EDTA produced a dose-related broncho-
`constriction that persisted for longer than 60
`minutes. The cumulative geometric mean
`PCzoFEVl was 2.4 mg/ml (range 1.2-12.8 mg/ml)
`for EDTA. This compares with a PCzoFEVl to
`BAC of 0.3 mg/ml (range 0.13-2.0 mg/ml) in the
`same subjects. Although not assessed in this
`study, it can be estimated on the basis of these
`and other findings17 that histamine is about 50
`times more potent as a bronchoconstrictor
`agonist than EDTA.
`
`Clinical Relevance
`Concentrations of EDTA in different nebulizer
`solutions vary from 0.1-0.5 mg/ml. Available
`evidence, although limited, suggests that the
`agent's presence in these concentrations is
`unlikely to cause significant bronchoconstriction.
`This view is based primarily on the observation
`that these concentrations are 2.5-25 times less
`than the concentrations of 1.2-12.8 mg/ml that
`cause significant bronchoconstriction in
`asthmatic subjects when inhaled alone.
`To investigate this possibility, the effect of
`EDTA on the bronchodilator response to a
`nebulizer solution containing both fenoterol and
`ipratropium bromide (Duovent outside the
`United States) was studied. On two occasions 18
`subjects with stable asthma inhaled fenoterol
`0.31 mg/ml and ipratropium bromide 0.13
`mg/ml, with and without EDTA 0.5 mg/ml.37 No
`significant difference in airway response was seen
`among the solutions. These findings contrast
`with the bronchoconstriction associated with
`Atrovent containing EDTA. They probably relate
`
`Table 1. BAC and EDTA Comparison of PC20FEVI and
`Concentrations in Commercially Available Nebulizer
`Solutions
`
`BAC
`
`Range of
`Concentrations
`(mg/ml)
`0.1-0.2
`
`(mg/ml)
`PC~OFEV~
`Geometric
`Range
`Mean
`0.1-2.07
`0.3
`0.9-2417
`4.0
`0.5-20'*
`5.0
`0.4-1618
`2.8
`0.1-1 .o
`EDTA
`1.2-12.87
`2.4
`PC2oFEV1 = the concentration required to produce a 20% fall in
`FEVl when inhaled by asthmatic subjects.
`
`to the more rapid onset of action and potent
`bronchodilator effect of fenoterol compared with
`ipratropium bromide, and the presence of BAC in
`addition to EDTA.
`Although these findings seem reassuring, they
`are relevant only to a single dose; the potential
`adverse effects associated with repeated use of
`bronchodilator nebulizer solutions containing
`EDTA have not been examined. Similarly, the
`potential effects of long-term use of EDTA remain
`to be determined.
`
`Bacterial Contamination
`Before a recommendation can be made to
`remove preservative agents from nebulizer
`solutions, it is necessary to consider whether this
`would be likely to lead to significant bacterial
`contamination. One of the characteristic features
`of the process of nebulization is the production
`of aerosol particles of a size that will reach the
`most peripheral airways ( c 5 p) and therefore
`bypass the protective mucociliary and cough
`reflex mechanisms operating in the upper airway
`Thus, the use of equipment or solutions that are
`contaminated with microorganisms potentially
`represents an effective method of delivering
`pathogens to the lungs and maintaining or
`spreading infections. This was originally
`recognized when outbreaks of pulmonary
`infection, usually with gram-negative bacteria,
`were traced to bacterial contamination of
`nebulizer solutions used in hospitals.3M2 These
`outbreaks were most frequently associated with
`ultrasonic and jet nebulizers delivering nebulizer
`solutions from large-volume, multidose bottles.
`A high frequency of bacterial contamination of
`nebulizer units and solutions also was identified
`in home care.4345 Review of these three studies
`illustrates many of the relevant issues.
`In a study of 52 patients requiring home
`treatment with nebulized albuterol, 61% of the
`
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`Page 6
`
`

`

`136
`
`PHARMACOTHERAPY Volume 18, Number 1, 1998
`
`solutions and/or aerosols were found to be
`In most cases, the nebulizer
`~ o n t a m i n a t e d . ~ ~
`reservoir and solution were sources of
`contamination; the most frequent organisms
`identified were gram-negative bacilli. The
`albuterol nebulizer solution available in Australia
`during the period of the study contained BAC in
`a concentration of 0.2 mg/ml.
`In a community-based study in Britain, over
`one-third of nebulizers were contaminated with
`bacteria.44 In contrast to previous studies, the
`most frequent isolates from aerosols and
`solutions were gram-positive cocci, most of
`which were of low pathogenicity. The high
`frequency of Staphylococcus albus, diphthoids,
`and micrococci isolates suggested transfer of
`organisms from the skin to the nebulizer
`chamber. In the case of albuterol, contamination
`was more frequent with the respiratory solution
`containing BAC than with prediluted unit-dose
`vials containing BAC at a lower concentration.
`The third study investigated the transmission
`of gram negative bacilli to asthmatic children
`through home nebulizer^.^^
`It confirmed
`observations that home nebulizers are common
`sources of aerobic gram-negative bacilli and that
`nebulization is capable of transmitting these
`microorganisms to the patient’s throat. As with
`previous studies, the major problem of
`contamination occurred with large-volume,
`multidose nebulizer solution bottles. Although
`25% of the children had recoverable anaerobic
`gram-negative bacilli in their throats after routine
`home nebulization, this did not result i n
`colonization of the upper respiratory tract, with
`none of the 20 subjects having gram-negative
`bacilli recovered from the throat swab before
`nebulization. Similarly, no known respiratory
`infections were recognized in the children during
`management with home nebulizers.
`These long-term observations are consistent
`with findings from previous studies in which the
`rapid clearing of inhaled bacteria occurred in
`47 and children.48 Thus
`both healthy
`respiratory defense mechanisms in people who
`are not acutely ill and live in their normal home
`environment appear to be highly effective.
`However, bacterial contamination of nebulizer
`solutions may still be associated with significant
`risks when used in certain circumstances, such as
`in patients with compromised pulmonary defense
` mechanism^.^^ It is also of concern that there
`have been documented episodes in which
`marketed nebulizer products have been
`contaminated with potential human pathogens
`
`such as Pseudornonas sp at the time of
`manufacture, despite the inclusion of BAC.
`Indeed, it has been proposed that the routine use
`of a preservative such as BAC in the manufacture
`of a nonsterile nebulizer solution may actually
`select for preservative-resistant strains of
`pathogenic bacteria.
`Together, these studies suggest that the
`inclusion of BAC in nebulizer solutions does not
`prevent bacterial contamination and that
`bacterial contamination is less likely to occur if
`the nebulizer solution is administered in unit-
`dose vials prepared under sterile conditions.
`
`The United States
`The current situation in the United States
`illustrates many of the prescribing, regulatpry,
`and commercial issues that must be considered.
`Despite the availability of a preservative-free
`albuterol nebulizer solution dispensed in unit-
`dose sterile plastic vials, alternative preparations
`of albuterol solutions containing BAC are still
`available and widely used (Table 2). These
`preparations, dispensed from either a multidose
`dropper bottle or a unit-dose screw-cap product,
`contain BAC in concentrations that can cause
`bronchoconstriction when inhaled by asthmatics.
`In contrast, in most other Western countries,
`preservative-free albuterol dispensed from a unit-
`dose sterile plastic vial is either the preferred
`product or the only albuterol nebulizer solution
`available.
`In addition, metaproterenol
`(orciprenaline) nebulizer solution containing
`BAC, which is still used in the United States, has
`been withdrawn from the market in other
`countries.
`The situation in the United States is even more
`questionable, when one considers Food and Drug
`Administration (FDA) regulations relating to the
`manufacture of
`solutions
`containing
`preservatives. The FDA requires only that
`manufacturers list that the product contains a
`preservative such as BAC, without documenting
`the concentration. Furthermore, prominent
`announcement as to the inclusion of preser-
`vatives such as BAC is not required, with the
`information often printed in small print on the
`back label, rather than on the front label.
`It is also noteworthy that the United States
`classifies various albuterol nebulizer products as
`therapeutically equivalent. This means that it is
`legal for a pharmacist to substitute one
`formulation for another without consulting the
`prescriber. As a result, a physician may prescribe
`
`Liquidia's Exhibit 1070
`Page 7
`
`

`

`PRESERVATIVES IN NEBULIZER SOLUTIONS Beusley et ul
`
`137
`
`Table 2. Presence of BAC in Albuterol Nebulizer Solutions Currently Available in the United States
`BAC Content Average
`of 2.5-mg Wholesale
`Volume of
`BAC"
`Albu terol
`Concentration Concentration 2.5-mg Dose Albuterol Dose
`Price
`($Ib
`(mg/ml)
`(mg/ml)
`(ml)
`(I%)
`
`Size
`(ml) Brand
`
`Manufacturer
`
`Product Type
`Mu1 tidose
`dropper bottle 20 Generic Glaxo
`Schering (Warrick)
`Proventil Schering
`Ventolin Glaxo
`3 Generic Alpharma
`Schering
`
`0.39'
`
`0.50'
`0.48'
`1.21
`
`1.63
`1.21
`1.40
`
`5.0
`
`0.1
`
`0.5
`
`50
`
`0.83
`
`0.1
`
`3.0
`
`300
`
`Unit-dose
`screw-cap
`(not sterile)
`
`Proventil Schering
`3 Generic Dey"
`Unit-dose
`Ventolin Glaxo
`sterile plastic
`nebule
`vial
`"The BAC concentrations in the different