Clinical Science and Molecular Medicine (1974) 46, 265-212.
THE POSSIBLE SITE O F ACTION O F S O D I U M
CROMOGLYCATE ASSESSED BY EXERCISE
CHALLENGE
S . G O D F R E Y , E. Z E I D I F A R D , K. B R O W N AND
J. H . BELL
Department of Paediatrics, Cardiothoracic Institute, London, and
Fisons Ltd, Pharmaceutical Division, Research and Development Laboratories, Loughborough
(Received 10 October 1973)
SUMMARY
I. The protective effect of different particle sizes of sodium cromoglycate (SCG)
was assessed by exercise challenge in nine asthmatic patients.
2. SCG particles of 11.7 pm or 2 0 pm mass median diameter were generated by a
spinning disc and compared with lactose placebo particles. The drugs were given 10
min before a 6 min run on a treadmill.
3. The post-exercise bronchoconstriction caused a 48% fall in peak flow rate in the
placebo test, a 41% fall after the large SCG particles and a 20% fall after the small
particles.
4. It is concluded that the site of action of SCG is probably in the smallest airways.
Key words : sodium cromoglycate, exercise-induced asthma, particle size, distribution
of particles.
A characteristic feature of most asthmatic patients is the way in which a typical brief attack
of asthma may be induced by the inhalation of an appropriate antigen (Aas, 1970). Exercise
also provokes a brief attack which has many similarities to this type 1 allergic reaction (Jones,
Buston & Wharton, 1962; Silverman & Anderson, 1972; Godfrey, 1973). The asthmatic
reactions can often be prevented by premedication with sodium cromoglycate if this is given
before antigen challenge (Pepys, Hargreave, Chan & McCarthy, 1968), or before exercise
challenge (Davies, 1968; Godfrey, 1970; Silverman & Andrea, 1972).
Sodium cromoglycate (SCG) is inhaled in the form of a powder and when presented in the
standard capsule (Intal) the particle size is mostly less than 6 pm in diameter; the inhaler
used clinically (Spinhaler) is designed to break up aggregates into fine particles. When used by
patients, about 25% by weight of the drug in the capsule is dispersed into particles below 6 ,urn
in size (Bell, Hartley & Cox, 1971) and about 5% by weight of the drug is in particles less than
2 pm in size (personal observations).
Correspondence: Dr S. Godfrey, Department of Child Health, Hammersmith Hospital, Du Cane Road,
London W12 OHS.
265
S. Godfrey et al.
266
It has been shown that when particles of about 2 pm enter the airways, they have a good
chance of reaching the smallest bronchioles while particles of about 10-12 pm will reach only
the large, proximal bronchi (Hatch & Gross, 1964). It occurred to us that the site of action
of SCG could be explored by investigating the protective effect of different particle sizes of the
drug on exercise-induced asthma.
METHOD
Studies were carried out on nine asthmatic patients aged 1 0 4 4 years as part of the assessment
of the effect of exercise. Some details of the patients are given in Table 1. All patients were
studied at the same time of day when in a stable state and not during an exacerbation of their
TABLE
1. Anthropometry of subjects and pulmonary dose of drug. 1 nmol of SCG 2
0.512 fig.
Dose of SCG received (nmol/kg)
Subject
S.A.
J.R.
S.N.
W.W.
I.E.
S.T.
C.T.
D.W.
D.S.
Mean
SEM
Sex
F
F
F
M
F
F
M
M
M
Age Height Weight
(years) (cm)
(kg)
Small particles
Large particles
162
162
151
168
140
154
140
142
146
25.8
36.3
33-4
27.3
28-9
16.4
29.4
30.0
26.3
27.7
31.2
44.3
31.6
25-8
25.8
32.6
36.3
22.3
28.3
1.95
30-8
2.1 5
44
27
25
32
11
13
13
10
11
13.2
50.5
44.5
86.4
31.0
394
31.8
31.2
38.5
illness. Each patient was studied once on 3 consecutive days inhaling either lactose placebo, or
small or large SCG particles in random order. No other drugs were taken for at least 6 h before
the test.
Simple lung-function tests were carried out before and after inhalation of the particles.
The peak expiratory flow rate (PEF) was measured with a Wright peak flow meter; the forced
expired volume in the first second (FEV1) and the forced vital capacity (FVC) were measured
with a water spirometer. In each test the best individual value from three attempts was recorded.
Particles of lactose or SCG were produced by the apparatus illustrated in Fig. 1 . The
aerosols of sodium cromoglycate were generated from aqueous solutions by using a spinning
top aerosol generator (May, 1966). The generator was placed at the top of the chamber, which
was approximately 2 m high and 0-5 m in diameter. The wet aerosol droplets were dried
during their passage down the chamber by a current of warm air, which was drawn in at the
top of the chamber. The subjects thus inhaled aerosols consisting of solid particles. The size
of particle was controlled by regulating the rotational speed of the disc and the concentration
of SCG in the solution.
Site of action of cromoglycate
267
The lactose particles were generated from a dry powder composed of finely ground lactose
by using the Wright dust feed mechanism (Wright, 1950). In contrast to the almost monosized aerosols of SCG, the lactose aerosol contained a spread of particle sizes which would be
deposited in all portions of the airways. During each test, frequent checks were made on the
Heater
Waste
extractor
fan
. .. . .
. .' . . .
.
.
.
. .
.
. .
.
particle size distribution of the aerosols by microscopic examination of a slide which had been
exposed in the chamber. The mass median diameter and geometric standard deviation of the
SCG particles were 2-0 pmf 1.2 and 11-7 pm+ 1-1 respectively. The lactose particles were
of all sizes between 1 and 20 pm.
The concentration of SCG inhaled by the patient was 19.5-29.3 nmol/l(10-15 pg/l) for small
particles and 156-195 nmol/l (80-100 ,ug/l) for large particles.
It was intended that each subject inhale 29.3 nmol (15 pg) of SCG per kg body weight.
Knowing the concentration of drug in the chamber and the quantity usually deposited in
tubing and mouth, the volume of each particle cloud to be inhaled was calculated for each
S. Godfrey et al.
268
subject. This usually meant inhaling 2-3 vital capacities of large particles and 20-30 vital
capacities of small particles. In the control experiments 10-15 vital capacities of the mixed
sized lactose particles were inhaled. The quantity of drug presumably passing the larynx was
calculated from the volume inhaled, the inspired concentration, the quantity deposited in the
tubing of the apparatus, the quantity collected in a filter through which the subject exhaled and
the quantity in a mouthwash performed by the subject immediately after completion of the
inhalations. The SCG concentration of washings was determined spectrophotometrically.
The inhaled dose is given in Table 1; the mean pulmonary dose was 24.2 nmol/kgf2*0
(S.E.M.) for small particles and 18.7 nmol/kg+2.3 (S.E.M.) for large particles.
As soon as the mouthwash was completed, lung function tests were performed and then the
exercise test was begun. The delay between inhalation and exercise was 10 min and did not
differ between different tests. Exercise testing was carried out on a motor-driven treadmill
as described previously (Connolly & Godfrey, 1970; Silverman & Anderson, 1972). Essentially
the subject ran (not walked) for 6 min at a slope of 10% and a speed adjusted to give a heart
rate of 170 per rnin in children and 150 per rnin in adults. The PEF was measured before
starting, every 2 rnin during exercise without stopping, and at frequent intervals for 20 rnin
after the end of exercise. For the assessment of response in this study, the % fall in PEF was
calculated as follows :
fall (%)
=
resting PEF -lowest PEF after exercise
x 100
resting PEF
The expected values for pulmonary function were taken from Godfrey, Kamburoff & Nairn
(1969) and Cotes (1968). Results were analysed by standard statisticalprocedures and differences
between studies were assessed by paired t tests.
RESULTS
Resting measurements
The mean resting PEF and FEV, were 55-60% of expected and FVC was SO-SO% of
expected, showing a moderate degree of airways obstruction to have been present. There were
no significant differences between values before and after inhalation of any one type of particle,
or between values for different types of particle (Table 2).
Exercise-induced asthma
After the inhalation of lactose placebo, all subjects developed post-exercise bronchoconstriction amounting to a fall in PEF of between 20% and 71%. There was a substantial
reduction of exercise-induced asthma in all but one subject after premedication with small
particles. After inhalation of large SCG particles two subjects showed more severe exerciseinduced asthma than after lactose, three had a similar amount and four had less exerciseinduced asthma (but in one of these cases there was much less protection than with small
particles). The detailed results are illustrated for one subject in Fig. 2 and the % fall in PEF
for each individual is shown in Fig. 3. The difference in % fall for the whole group (Table 2)
was highly significant when comparing small particles with either lactose (P<O*OOl)or large
particles (P<O.Ol). There was no significant difference in % fall between lactose and large
particles (P>0-5).
59
7
Mean
SEM
55
63
54
D.W.
D.S.
73
48
54
106
40
40
Predrug
FEVl
(% of
expected)
S.T.
C.T.
S.N.
W.W.
I.E.
S.A.
J.R.
Subject
59
7
73
46
58
104
48
34
50
68
54
60
10
48
6
24
54
103
34
71
70
104
30
55
50
20
67
55
24
71
45
47
57
Post-drug Post-exercise Pre-drug
FEVl
fallinPEF
FEVl
(% of
(% of
(% of
expected)
resting)
expected)
Lactose
63
9
32
58
83
31
59
82
66
101
-
4
20
31
25
6
15
0
24
33
20
26
58
8
42
60
58
20
58
71
104
33
74
Post-drug Post-exercise Predrug
FEVl
falIinPEF
FEVl
(% of
(% of
(% of
expected)
resting)
expected)
Small particles
60
8
29
63
50
27
62
74
109
50
73
41
8
34
52
51
9
73
61
18
59
15
Post-drug Post-exercise
FEVl
fall in PEF
(% of
(% of
expected)
resting)
Large particles
TABLE
2. Resting pre- and post-drug FEV,, and % fall in PEF due to exercise. Details of resting PEF and FVC can be supplied by the
authors on request.
%-
(%
s
%
2
x
8
g.
5
3
S. Godfrey et al.
270
300r
0
5
15
10
20
Time ( m i d
FIG.2. Exercise-inducedasthma in one subject after inhaling different particles. A, Small particles;
n,large particles; 0 , lactose.
70-
60 -
-rn
50 -
-
._
g!
40-
--5
30Q
c
._
9
20 -
10-
0-
U
Lactose
I
Small
part ides
U
Large
particles
FIG.3. Results for all subjects showing the exercise-induced asthma in relation to inhaled particles.
Site of action of cromoglycate
27 1
DISCUSSION
This study has shown that, for most asthmatic subjects, 2.0 pm particles of SCG cause substantially greater suppression of exercise-induced asthma than 11*7 pm particles. The obvious
conclusion to be drawn is that SCG must act on a peripheral site in the lung, but there is
another possibility which must be considered, namely a numerical or area-related effect,
Since the weight of both particle sizes inhaled was kept similar, the actual number of small
particles would be approximately 200 times the number of large particles, the volume of a
sphere of radius r being 4/3 IIr3. By similar reasoning, the total surface area of this number of
small particles would be some 6 times that of the large particles, since the area of a sphere is
413r2.Now it is possible that the larger number or area of the smaller particles was responsible
for their greater effect either because they were able to saturate more receptor binding sites
or because they dissolved more rapidly in the region of these sites. On the whole, these hypotheses seem unlikely because they would imply either that the small particles should be 200
times as effective as the large particles or possibly 6 times as effective. Looking at the results in
Table 2, it can be seen that small particles reduced exercise-induced asthma by approximately
58% (from 48 to 20) while large particles reduced it 17% (from 48 to 41). This represents
roughly a threefold difference on average and is less than predicted by the numerical or sizerelated hypotheses.
The commercially available form of SCG delivers approximately 7 mg of the compound in
particles less than 6 pm in size when inhaled, and calculations based on data from the present
experiments suggest that some 6040% of this weight enters the lungs. The degree of suppression of exercise-induced asthma by the commercial preparation is usually of a similar order to
that found here with 2-0 pm particles; in eighty patients given the commercial compound, the
mean exercise-induced fall in PEF after placebo was reduced by 56% (P. Konig & S. Godfrey,
personal observations). This formulation must deposit many more particles than in the
present experiments and the lack of any greater suppression of exercise-induced asthma
suggests that dose is a relatively unimportant determinant of the effect of particles of different
sizes.
The alternative conclusion to be drawn from the results of this study, namely that the
difference of effect is due to the different penetrations of small and large particles, implies that
it should be possible to determine the site of action of the drug. Crucial to this argument is the
homogeneity of particle size and the likely distribution of particles in the lung. The method
used to generate the particles gave a very uniform size, as assessed by the geometric standard
deviation, and because SCG is relatively insoluble, little change due to water effects would be
expected when the dry powder was inhaled. A check on this was carried out by humidifying
particles under the microscope and no change in size was noted. The fate of the inhaled
particles depends upon factors such as tidal volume and flow rate as well as size and our
conclusions about the likely site of deposition are based on the analysis of these factors by
Hatch & Gross (1964). However, the data upon which they based their calculations were
obtained from studies on normal subjects. Although our patients were relatively well at the
time of inhalation, they had some airway obstruction and nothing is known for certain about
particle distribution in this situation. Changes in flow rate would be unlikely to affect the
distribution of 2 pm particles since they are believed to deposit in terminal bronchioli or alveoli,
where the flow is already so slow and the cross-sectional area so large. With the patients
272
S. Godfrey et al.
breathing deeply and slowly, it is also rather unlikely that the deposition of the larger particles
would be much affected by the moderate airways obstruction since this probably affects
smaller airways than those in which the particles normally deposit. Evidence to support this
concept can be found in the studies of Benatar & Konig (1974), who showed relatively poor
gas-density dependence of flow in a similar group of subjects before exercise and concluded
that this represented more peripheral obstruction.
The patient to patient variation of response (Table 2) is difficult to explain on the numerical
or area hypotheses, but could be explained by slightly different distribution of particles due
to differences in the major sites of airways obstruction.
However, in order to settle this point, further experiments will be needed with particles of
intermediate sizes and possibly with different inhaled weights of particles. The results presented
in this paper must be regarded as suggestive that SCG acts primarily on receptors in or around
the terminal airways and alveoli, but final proof has yet to be established.
ACKNOWLEDGMENTS
We thank Dr D. C. F. Muir and Dr R. E. C. Altounyan for their advice and Miss T. Andrea
and Mr J. Peachey for technical help. This work was supported by the Asthma Research
Council.
REFERENCES
AAS,K. (1970) Bronchial provocation tests in asthma. Archives of Disease in Childhood,45,221-228.
BELL,J.H., HARTLEY,
P.S. & Cox, J.S.G. (1971) Dry powder aerosol. I. A new powder inhalation device.
Journal of Pharmaceutical Sciences, 60, 1559-1 563.
BENATAR,
S.R. & KONIG,P. (1974) Maximal expiratory flow and lung volume changes associated with exerciseinduced asthma in children and the effect of breathing a low density gas mixture. Clinical Science and
Molecular Medicine. (In press).
CONNOLLY,
N.M. & GODFREY,
S. (1970) Assessment of the child with asthma. Journal of Asthma Research, 8,
31-36.
COTES,J.E. (1968) Lung Function, 2nd edn. Blackwell Scientific Publications, Oxford.
DAVIES,
S.E. (1968) The effect of disodium cromoglycate on exercise-induced asthma. British Medical Journal,
iii, 593-594.
GODFREY,
S. (1970) The effect of disodium cromoglycate on asthma induced by exercise. In: Proceedings of the
VZZ Znternatioizal Congress of Allergology, Florence, Italy, pp. 3540. Edizioni, C.E.P.I., Roma.
GODFREY,S. (1973) In: The Ninth Symposium on Aduanced Medicine, pp. 293-299. Ed. by Walker, G. Pitman
Medical, London.
S., KAMBUROFF,
P.L. & NAIRN,
J.R. (1970) Spirometry, lung volumes and airway resistance in normal
GODFREY,
children aged 5-18 years. British Journalof Diseases of the Chest, 64,15-24.
P. (1964) Pulmonary Deposition and Retention of Aerosols. Academic Press, New York.
HATCH,T. & GROSS,
JONES,R.S., BUSTON,
M.H. & WHARTON,
M.J. (1962) The effect of exercise on ventilatory function in the child
with asthma. British Journal of Diseases of the Chest, 56,78-86.
MAY, K.R. (1966) Spinning top homogeneous aerosol generator with shockproof mounting. Journal of
Scientific Instruments, 43,841-842.
PEPYS,
J., HARGREAVE,
F.E., CHAN,M. & MCCARTHY,
D.S. (1968) Inhibitory effects of disodium cromoglycate
on allergen-inhalation tests. Lancet, ii, 134-137.
SILVERMAN,
M. & ANDERSON,
S.D. (1972) Standardization of exercise tests in asthmatic children. Archiues
of Disease in Childhood, 47,882-889.
SILVERMAN,
M. & ANDREA,
T. (1972) Time course of effect of disodium cromoglycate on exercissinduced
asthma. Archives of Disease in Childhood, 47,419422.
WRIGHT,B.M. (1950) A new dust feed mechanism. Journalof Scientijc Instruments, 27,lZ-15.