Temazepam is one of the best benzodiazepines. Yes by weight it is not as potent on a WEIGHT basis than a lot of other benzos, but guess what? That means shit. Benzos are and have always been compared to each other solely based on their ability to produce equal anxiolytic effect, similar to how opioids are compared to one another based on equianalgesic effect.
So temazepam 20mg produces the same level of anxiety relief as 0.5mg alprazolam or 0.5mg clonazepam or 10mg of diazepam. But at those doses, temazepam is more hypnotic, sedative, euphoric, relaxing and more recreational all around. There are studies out there, I know of one big study which compared many benzos on their reinforcing abilities. In that mid-80's study, triazolam and temazepam maintained higher rates of self-injection in both human and animal subjects compared to a variety of other benzodiazepines (other examined: diazepam, lorazepam, oxazepam, flurazepam, alprazolam, chlordiazepoxide, clonazepam, nitrazepam, flunitrazepam, bromazepam, and clorazepate). Studies on the pharmacokinetics of various benzos (at least 2, a British study and an Australian one), showed that temazepam was more rapidly absorbed than most other benzos. It's established science that drugs with a more rapid absorption rate are more prone to produce drug-liking and addictive behavior. Triazolam also has a very rapid absorption rate, coincidently.
And outside the North American bubble, temazepam was the most widely abused benzo in Europe, especially the UK. Australia had a major temazepam abuse problem for years. In 1990's and early 2000's, temazepam accounted for most benzodiazepine sought by forgery of prescriptions and through pharmacy burglary. Pharmacists and their staff often encountered aggressive and threatening behaviour from people seeking temazepam. There were 537 burglaries on Victoria's 1200 pharmacies from 1 January to 30 August 2001, including 'ram raids', (using cars to smash through windows). Temazepam was almost always the benzo that was demanded and it appeared to be the main target in many pharmacy burglaries. Temazepam is sought in 85% of all reported benzodiazepine forgeries. As a result of its rampant abuse, the Australian government made a decision to restrict temazepam and put it under a much more restrictive schedule than it previously was (placed alongside barbiturates, potent opioids, etc.). Once physicians stopped prescribing it due to its more restrictive scheduling, abuse rates went down dramatically. In 2004, the Australian government put it back in the same schedule as other benzos, but is not typically prescribed anymore. It's been replaced by zolpidem and other Z-drugs.
The problem with temazepam abuse in the UK in the 80's and 90's was even worse, death due to acute temazepam intoxication and overdose was a frequent occurrence. In 1999, temazepam was implicated in about a third of all drug deaths, either alone or in combination with another downer like alcohol or heroin. The frequency of deaths occurred with the ingestion of temazepam alone was/is of major concern, mainly because a majority of drug users believe that benzodiazepines are not lethal when ingested alone, even in massive quantities. Although most benzodiazepines are considered to have a relatively high therapeutic index and overdose is a rarity, temazepam has consistently been shown to be far more lethal in overdose than other benzodiazepines. Over 10 years in the United Kingdom, 1512 fatal poisonings have been attributed to benzodiazepines with or without alcohol. These were compared with prescription data to establish a fatal toxicity index (deaths per million prescriptions) for each benzodiazepine. Similar indices have been derived for barbiturates and antidepressants. There were clear differences between benzodiazepines. Temazepam by far had the highest number of deaths per million prescriptions at 11.9 (95% confidence interval 10.9 to 12.. ); above that of some tricyclic antidepressants. In contrast, oxazepam had an index of 2.3 (1.2 to 3.4), and the average index for all benzodiazepines combined was 5.7. In the UK temazepam remains highly restricted and placed in Schedule 3 (midazolam and flunitrazepam are also Schedule 3), while all other benzodiazepine are Schedule 4.
Another study, this time in Australia, 303 patients who had ingested a benzodiazepine alone or in combination with alcohol and presented to a general hospital which served a well defined geographical area. Again, oxazepam produced less and temazepam more sedation than other benzodiazepines. Unadjusted odds ratios for coma with oxazepam and temazepam compared with other benzodiazepines.
During 1991-3, 542 patients with benzodiazepine poisoning presented to this hospital, 239 of these patients, however, had ingested either more than one benzodiazepine or coingested other sedating drugs. The drugs ingested by the remainder were temazepam (64), oxazepam (45), diazepam (1 13), clonazepam (24), flunitrazepam (21), nitrazepam (18 ), others Details of coma scores and odds ratios of the benzodiazepines ingested showed that temazepam was significantly more toxic than most other benzodiazepines. Two out of the 45 subjects (4) who ingested oxazepam were stuporous or comatose, 38 out of the 194 subjects (19)who ingested other benzodiazepines (clonazepam, diazepam, flunitrazepam, nitrazepam and others) were stuporous or comatose, while 16 out of the 64 subjects (25) who ingested temazepam were stuporous or comatose. None of the oxazepam subjects were comatose, 16 out of the 194 subjects (who ingested other benzodiazepines were fully comatose, and 9 out of 64 subjects (14) who ingested temazepam were fully comatose.
It's sort of similar to how morphine and heroin are less potent by weight than hydromorphone or oxymorphone, yet heroin/morphine have a higher incidence of, and more profound effects - higher rates of sedation, drowsiness, euphoria, respiratory depression, itchiness, constipation, nausea and vomiting. It's in all the medical literature which physicians follow. When patients have pre-existing respiratory issues or sensitivity to morphines powerful side effects, often hydromorphone is the alternative. In some cases, fentanyl may be more appropriate. Oxymorphone actually has a higher incidence of effects than hydromorphone, but lower than morphine. In terms of cognitive abilities, one study has shown that morphine may have a negative impact on anterograde and retrograde memory, although minor. This does not occur in many of the other potent opioids.
Weight potency has absolutely NOTHING to do with how good a particular drug is.