Heroin is a chemically altered form of which substance?

Heroin is a chemically altered form of morphine, which explains why the correct answer is morphine. Morphine is a naturally occurring alkaloid extracted from the opium poppy and is used for its potent analgesic properties. The chemical alteration involves the addition of two acetyl groups to the morphine molecule, resulting in heroin, also known as diacetylmorphine. This modification not only increases the drug’s potency but also affects its pharmacokinetics, leading to faster brain penetration compared to morphine.

This transformation from morphine to heroin is significant in understanding the pharmacology of opioids and the associated risks of addiction and dependency. Recognizing the connection between these two substances highlights the continuum of opioid use and misuse. The other options do not pertain to heroin; for instance, cocaine is a stimulant derived from coca leaves, marijuana is a plant-based substance, and codeine is another opioid, but it is not the direct precursor of heroin.