|US|| Prescription Only (Schedule II, III)|
Schedule V in combinations
|Canada||OTC when mixed with other drugs|
|Onset of Action||30-60 minutes|
|Duration of Action||6-8 hours|
Dihydrocodeine, or DHC, is an opioid painkiller very similar to codeine, differing only in relative potency (twice as potent by weight) and duration of effect (half life is 4 hours rather than 3 for codeine).
Dihydrocodeine is available by prescription only in the United States, and is classified as a Schedule II controlled substance. It is rarely prescribed, however. In Canada, the UK, and other countries, it is available over the counter in combination products such as cough syrup.
For more information on the effects of dihydrocodeine, please view the codeine article. Dihydrocodeine is listed here in addition to codeine because it is a very similar drug that is more widely available and/or cheaper than codeine in some countries.
Comparison to codeine
Dihydrocodeine is approximately twice as potent per milligram as codeine. The bioavailability is also lower than codeine, at around 20%, versus up to 90% for codeine. This means that, while DHC taken orally is twice as potent as codeine, consuming DHC via other routes (via insufflation, rectally, etc.) has the potential to enhance its effect.
The duration of action for DHC is typically cited at 6-8 hours, versus 4-6 hours for codeine. The half-life of DHC is 4 hours, as opposed to codeine, which derives its analgesic effect from the metabolites morphine (half life of 2-3 hours) and Codeine-6-glucuronide (C6G) (half life of 2 hours).
Codeine typically registers on standard drug tests, at least according to official test specifications. Morphine, converted from codeine in small amounts, is typically listed on drug tests.
Dihydrocodeine, conversely, is usually not detected by 5-panel drug tests (opioids, amphetamines, cannabis, cocaine, and PCP). Even in the event of a positive test result for opioids, many laboratories only test samples for morphine. As DHC is largely unknown in the United States, testing specifically for it is rare. However, according to anecdotal reports, it is possible for users to register positive on a drug test after taking DHC.