> Traditional opioids mimic opium, a compound found in the poppy plant that contains morphine. Huh? How can a compound contain another compound. I thought opium was the term for an extract which contained opiates (compounds) and not the other way round.
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"Opium" is the dried latex (milky fluid) that comes from the seed capsules of the opium poppy (Papaver somniferum).
Opium contains ~12% morphine, ~2.5% codeine, and ~1.5% thebaine, all of which are analgesic alkaloids that act on the μ-opioid receptors. So opium itself is a cocktail of these, plus non-analgesics like noscapine (a cough suppressant) and papaverine (a vasodilator.)
Heroin is synthesized from morphine by acetylation.
Oxycodone is synthesized from thebaine in a more complex, multi-step process.
As for the terms "opiate" vs. "opioid", the terms are sometimes used interchangeably but "opiate" generally refers to naturally occurring chemical (morphine, codiene, thebaine, etc.) while "opioid" is a catch-all Heroin is often lumped in with the opiates since it is a simple synthesis; oxycodone could be called a "semi-synthetic" opioid, and fully synthetic opioids include fentanyl, methadone, and tramadol. Relative to morphine, codeine is about 1/10th the potency, heroin is 4x, fentanyl is 50-100x, and the veterinary analgesic carfentanil (given to elephants and rhinos) is 10,000x--yikes!