I don't have much info on these lozenges, but other similar products of the time tended to be based on cayenne pepper. Later in the 19th century, cocaine also became a popular ingredient, albeit in very small amounts.
In 1844, according to the Eclectic Magazine, Dr Stolberg "bequeathed the secret of his voice lozenge - with presents of which he was wont to secure the friendship of the first vocal artists of his day - to a gentleman of large wealth in this country." The lozenges were still around, under the same name, at the end of the 19th century.
Image: from Almanach comique, pittoresque, drolatique, critique et charivarique pour l'année 1887 , reproduced courtesy of Old Book Illustrations
TO MEMBERS OF PARLIAMENT. DR. STOLBERG'S VOICE LOZENGE, for Im- proving the Voice, and removing all affections of the Throat, strongly recommended to Clergymen, Singers, Actors, Public Speakers, and all persons subject to Relaxed Throats. The above Lozenge has been before the public for three years and is proved by the most cele- brated artistes, who continue their constant use, to be the best specific ever invented for the Voice and Throat; a trial will prove their un- doubted efficacy. Testimonials are published with each box from Ma- dame Grisi, Madame Persiani, Madame Eugenie Garcia, Signor La- blache, &c., &c. Wholesale Agents, Barclay and Sons, Farringdon-street; Sutton and Co., Bow Churchyard; W. Edwards, Newberry and Sons, St. Paul's Churchyard; Sanger, Dietrichsen, and Hannay, Oxford-street, and Retail by all respectable Chemists in the Kingdom.
Source: The Daily News, Monday 30 March 1846