Opium derivatives have been used for thousands of years. Morphine saw prominent use in the United States as an anesthetic in the late nineteenth and early twentieth centuries, but this use declined for a variety of reasons.

A search for alternatives to barbiturate anesthetics sparked renewed research interest in Opioids in the 1950s. Fentanyl was first synthesized in 1960, and from 1969 onwards became the opioid of choice for anesthesia.

The first illicit fentanyl was identified in 1970, sold first in California and referred to as “China White” or “Synthetic Heroin.” A UCLA illicit narcotics study identified some 110 overdose deaths from illicit Fentanyl in the years 1981-1987. Another study of ER patients at one teaching Hospital in Pittsburgh found 18 of 59 total overdoses in the period 1987-1988 were caused by Fentanyl. Medical fentanyl also saw illicit use in the 1990s with the introduction and abuse of transdermal Fentanyl patches.

Why wasn’t Fentanyl “more widely used and abused”?

Partly this was perception, and some of this abuse was invisible, because Fentanyl was often regarded as a subset of Heroin, which the public was more familiar with. Media narratives lumped “synthetic heroin” as part of more common Heroin abuse. Overdose deaths might be categorized as heroin overdoses or undifferentiated opioid overdoses. Fentanyl abuse and overdoses from 1970-1990 were undercounted and underreported, because people simply were not looking for it.

Partly this was logistics. Fentanyl is relatively cheap to produce, but requires sophisticated chemistry knowledge, equipment, and precursor chemicals which could be difficult for narcotics traffickers to obtain.

Partly this relates to the vagaries of illicit markets, which are sometimes distorted in curious ways by policing and prohibition. Use of different narcotics tends to see waves of usage of different narcotics. Partly this is novelty driven, similar to the trends observed in the legal alcohol market (the craft brew fad, alcopops, whiskey boom, wine coolers, etc). Partly this represents traffickers transitioning to different products when police begin to target popular narcotics.

The explosion of modern Fentanyl abuse comes within the 20 year rule, I would say a number of the key modern conditions were not really present within the US in the 1970s and 1980s, but I can't give you a detailed analysis of that under this subreddit's rules.

There is fair amount of recent journalism on this, so I will provide the briefest possible introduction so you can look up the debate yourself, but I'm not going to meaningfully discuss this or answer follow up questions on recent events:

Recent illicit fentanyl boomed in mainland China due to a combination of ready access to skilled chemists and precursors; and ineffective policing. Sources cite a variety of factors in the PRC's ineffective policing response. Some of these factors are controversial and intersect with current politics or geopolitics.