The following is from The London Practice of Physic, published in 1779:
Of the HICCUP.
The hiccup is a convulsive spasm of the œsophagus, the muscles serving for deglutition, and the stomach; the diaphragm was by some thought to be in fault, but without any foundation.
Hippocrates observes, that it may proceed either from too much emptiness or fullness, particularly of the brain; sometimes it is local in the stomach. Much depends on its being a symptomatic or a primary disease.
The musk julep has proves serviceable in this disorder, when symptomatic, and attended with flatus; also the following;
R Spirit. volat. fœtid.
Tinctur, succini, aa 3ij. furnat gutt. L. fabine e cochl. ij. julep. e Moscho
Add some drops of laudanum, as you think proper, to the medicines above.
Sternutatories frequently give relief; and emetics, when it arises from the stomach.
Laudanum was a potent narcotic—a tincture composed of opium and morphine. It was an ancient remedy, in existence since Roman times, and during the eighteenth century it was used to treat a variety of maladies and wounds. When Alexander Hamilton was shot in his duel with Aaron Burr, he was quickly administered laudanum. The substance is still used today (albeit in a more regulated form) to treat diarrhea and in easing withdrawal symptoms in addicts.
The 1811 edition of The London Practice of Physic smartly added the following:
Retaining the breath for a considerable time; any sudden surprise or fright; swallowing water, or what is preferable, a tea-spoonful of vinegar very slowly, holding the breath at the same time as long as possible, often puts a stop to it, when it arises from an accidental cause.