Nicomorphine is an ester of morphine 2 to 3 times stronger than morphine, in fact the only difference with diamorphine (smack) is that nicomorphine has nicotinyl at the 3 and 6 positions (the precursor in question is the acid anhydride of niacin, Vitamin B₃) rather than acetyl groups . . .
Prior to the invention of the antihistamines in the 1940s and the work on corticosteroids which showed their efficacy around the same time, the preferred drugs for allergies and pulmonary conditions were in fact amphetamines, belladonna alkaloids, and narcotics, with dihydrocodeine, codeine, dionine, hydrocodone, and whole opium being used most frequently, smack being used too when it was legal, with some use of oxycodone, hydromorphone, morphine, and dihydromorphine as well, and enough experimentation with pethidine in the last years of that dispensation to see it didn't really help . . . prior to 1914, and later in some countries, cocaine was much used by allergy & pulmonary doctors, on their patients, I mean . . . barbiturates also had some use in the field. Theophylline was discovered for this a while ago as well, and I think there was actually a chocolate alkaloids hydrochlorides preparation, like the chocolate analogue of Pantopon, in the 1930s.
The fact that the only decongestants which really work are precursors for meth, E, 4-methylaminorex and company is really no surprise -- part of the early work on amphetamine was to get an ephedrine (the wonder drug of the 1880s) which had fewer side effects. The technique of using a drying agent like belladonna, atropine, hyoscine and so on is echoed mainly in diphenhydramine, which was indeed originally the result of French research to get a hyoscine (scopolamine) replacement with a more favourable therapeutic index. Also, when I was given methylphenidate for low blood pressure and dextroamphetamine for somnolence when I was on a rapidly increasing dose of hydromorphone, both of them worked on stuffiness 100 times better than pseudoephedrine. Ephedrine has a dirtier side effect profile including raising blood pressure more -- which is why it works great mixed with oxycodone or oxymorphone and scopolamine as a painkiller.