Methods and uses are described for treating or preventing diseases of
humans or non-human animals by reducing the amount of active leukotriene
B.sub.4 (LTB.sub.4) in those in need of such treatment using LTB.sub.4
hydroxylases. In certain embodiments, LTB.sub.4 hydroxylase is
administered in combination with nicotinamide adenine dinucleotide
phosphate and/or an NADPH-cytochrome P-450 reductase. The invention is
particularly useful for treating or preventing respiratory diseases that
are caused or exacerbated by inflammation.