This article is from the Asthma FAQ, by Patricia Wrean and Marie Goldenberg email@example.com with numerous contributions by others.
Some asthmatics find the dry powder inhalers more effective than
their MDI (aerosol) counterparts. It is suspected that the
aerosol or propellant in the MDI may act as an irritant to some
asthmatics, as in the following article:
J.R.W. Wilkinson et al., Paradoxical bronchoconstriction in
asthmatic patients after salmeterol by metered dose inhaler,
British Medical Journal 305 (1992) 931. The first sentence
in the conclusion is: "Bronchoconstriction after both
salmeterol and placebo by metered dose inhaler but not after
salmeterol by diskhaler suggests that the irritant is not
the salmeterol itself." . . . "The similarity in characteristics
of bronchoconstriction after beclomethasone by metered dose
inhalers implicates one or both chlorofluorocarbons . . . as
the irritant. That salbutamol caused no bronchoconstriction was
attributed to its faster onset of action opposing any
bronchoconstrictor effects of the propellants."
** However, according to the 1994 Physicians' Desk Reference,
Intal Spinhaler capsules are "contraindicated in those
patients who have shown hypersensitivity to . . . lactose."
So asthmatics who are lactose-intolerant may not have this
form of cromolyn sodium as an option.