While there is only one reference by Pepys to opium, over the years there has been a healthy discussion in the annotations about its uses and abuses in the 17th century.
Epidemics of malaria periodically decimated the population of England. What to do?
Hope seemed to come from exotic and dangerous sources, as the curative powers of quinine were discovered by the Jesuits in Peru in the 17th century. It became known as "Jesuits' Powder."
The cure got off to a rocky start in England, where loyal Protestants viewed it as part of a Jesuit plot to take over the country. Oliver Cromwell died of malaria at a relatively young age rather than avail himself of dastardly Jesuitical medicine.
Charles II was more fortunate. He was the beneficiary of what the Jesuits of the time might have called a strict mental reservation -- and what Pascal might have called a lie.
"In 1672 Robert Talbor, who described himself as a feverologist, published a book that carefully avoided any mention of the ingredients of his own remedy but warned others: Beware of all palliative cures, and especially of that known as Jesuits' Powder, for I have seen most dangerous effects follow the taking of that medicine.
"That warning was duplicitous: Talbor was mixing Jesuits' Powder with opium and various wines, thus disguising it from detection.
"In 1678 a malaria epidemic broke out around London, and it was not long before Charles II contracted the disease. News of Talbor's success in curing people reached the king. Despite the fact that Talbor was considered a quack by the College of Physicians, the king demanded his services. Talbor cured the king."
According to Hazelmary, who does not give us a citation:
Charles II rewarded Robert Talbor with an honorary knighthood and he was appointed Royal Physician.
"In 1678 Charles II sent Talbor to the French court where Louis XIV's son was suffering from malaria. He was pressed by Louis XIV to reveal his secret with an offer of 3,000 gold crowns and a substantial pension for life for the right to publish the secret upon his death.
"When Talbor died in 1681, at age 42 Louis XIV released Talbor's formula, and it was published in London the following year."