Hydrocodone

hydrocodone (commonly sold as vicodin when combined with paracetamol) is a semi-synthetic opioid morphinan synthesized from codeine, one of the opioid alkaloids found in the opium poppy. it is a narcotic analgesic used orally as a cough suppressant, but also commonly taken orally for relief of moderate to severe pain. those who take hydrocodone for recreational purposes report a sense of relaxation and euphoria, especially at higher doses.

hydrocodone is prescribed predominantly within the united states, with the international narcotics control board reporting that 99% of the worldwide supply in 2007 was consumed in the united states.

like many opioids, such as dextropropoxyphene, hydrocodone is often combined with acetaminophen (paracetamol) to enhance analgesia and deter abuse. acetaminophen overdoses and long-term use, often due to recreational use, can cause serious or fatal liver damage. currently, the only brand of hydrocodone in the united states that does not have acetaminophen is zohydro er which comes in doses of up to 50mg.

chemistry

hydrocodone, or 3-methyl-dihydromorphinone, is an opioid of the morphinan class. hydrocodone and other molecules of this class contain a polycyclic core of three benzene rings fused in a zig-zag pattern called a phenanthrene. a fourth nitrogen-containing ring is fused to the phenanthrene at r₉ and r₁₃, with the nitrogen member looking at r₁₇ of the combined structure. this structure is called morphinan.

hydrocodone, along with other morphinans, contains an ether bridge between two of its rings, connecting r₄ and r₅ through an oxygen group. it contains a carbonyl group bound at r₆ and a methyl group located on the nitrogen atom at r₁₇. the carbon-oxygen double bond of the carbonyl saturates the benzene ring it is bonded with, thus hydrocodone lacks the double bond on that ring found in codeine.

hydrocodone also shares the 3-methoxy substitution found in codeine; the two differ only from their r₆ substituents. hydrocodone is analogous to the other morphinans including dihydrocodeine, heroin, ethylmorphine, codeine, and oxycodone.

pharmacology

the euphoria, anxiety suppression and pain relief effects appear to stem from the way in which opioids mimic endogenous endorphins. endorphins are responsible for analgesia (reducing pain), causing sleepiness, and feelings of pleasure. they can be released in response to pain, strenuous exercise, orgasm, or excitement. this mimicking of natural endorphins results in the drug’s effects.
it acts primarily on μ-opioid receptors, with about six times lesser affinity to δ-opioid receptors.

in the liver, hydrocodone is transformed into several metabolites. it has a serum half-life that averages 3.8 hours. the hepatic cytochrome p450 enzyme cyp2d6 converts it into hydromorphone, a more potent opioid.

taking hydrocodone with grapefruit juice may enhance its psychoactive effects. it is hypothesized that the cyp3a4 inhibitors in grapefruit juice may interfere with the metabolism of hydrocodone, although there has been no research into this issue.