Comparison of Benzodiazepine Pharmacology
| Benzodiazepine | Onset of Action (min) | Half-life* (hrs) | Comp. Oral Dose** Ashton | Comp. Oral Dose** ClinCalc.com |
|---|---|---|---|---|
| Alprazolam (Xanax®) | 15-30 | 6-20 | 0.5 mg | 0.75 mg (0.5 – 2 mg) |
| Bromazepam (Lexotan®, others) | 15-30 | 8-30 | 3 mg | – |
| Chlordiazepoxide (Librium®, Limbitrol®) | 15-30 | 5-100 | 10 mg | 33 mg (12 – 50 mg) |
| Clobazam (Onfi®)*** | 20-30 | 42-47 | 20 mg | – |
| Clonazepam (Klonopin®, Rivotril®) | 15-30 | 18-39 | 0.5 mg | 0.75mg (0.5 – 4 mg) |
| Clorazepate (Tranxene®) | 15-30 | 50-100 | 7.5 mg | 13 mg (8 – 30 mg) |
| Diazepam (Valium®) (reference) | 0-15 | 20-100 | 10 mg | 10 mg |
| Flurazepam (Dalmane®) | 0-15 | 47-100 | 30 mg | 20 mg (8 – 30 mg) |
| Lorazepam (Ativan®, Loreev®) | 15-30 | 10-20 | 1mg | 1.3 mg (1 – 4 mg) |
| Midazolam po (Versed®) | 0-15 | 1-4 | – | 7 mg (5 – 10 mg) |
| Oxazepam (Serax®) | 30-60 | 3-21 | 15 mg | 20 mg (5 – 40 mg) |
| Quazepam (Doral®) | 15-30 | 28-114 | 5 mg | 27 mg (15 – 40 mg) |
| Temazepam (Restoril®) | 30-60 | 10-20 | 30 mg | 20 mg (5 – 40 mg) |
| Triazolam (Halcion®) | 15-30 | 1.6-5.5 | 0.5mg | 0.25 mg (0.25 – 1 mg) |
*Half-life is the time it takes for your body to metabolize half of the drug, and includes active metabolites (e.g., oxazepam is a metabolite of diazepam).
** Comparative Oral Dose: Since there is no standard, equivalencies vary between the sources. This table was compiled from the two sources shown in the table, and was checked against four others.[2,3,4,5]
*** Accumulates 23-fold over 2 weeks
Note that there is a variety of half-lives and potencies. The time for “onset of action” is how long it takes for you to feel the drug’s effects. “Half-life” is a measure of how long it takes until half of the drug becomes inactivated. Since several of the benzos are metabolized into other benzos, to understand the full impact of a benzo, you must include its active (benzo-like) metabolites, as this table does. Some metabolites have no or limited benzo-like activity, though they may have other effects, including adverse effects. A complete list of benzos, along with pharmacokinetic properties, can be found here.
Benzo dosages vary widely. As you can see from the table, taking a “low dose” is meaningless unless you are using a comparative scale, such as the one in the table. For example, according to Ashton, Xanax is 20 times more powerful than Valium, and clonazepam is 60 times more powerful than temazepam. Using the modern ClinCalc ranged data, Xanax is 5-20 times stronger than Valium, and clonazepam is 1.25-80 times more powerful than temazepam.