Benzodiazepines are a class of medications primarily used for managing anxiety, insomnia, and seizures. Understanding the variations in their pharmacological properties is crucial for healthcare professionals and patients alike. This article delves into a comparison of different benzodiazepines, focusing on their onset of action, half-life, and relative potencies, summarized in a Benzo Potency Chart. This information is vital for making informed decisions about medication management and ensuring patient safety.
The following table provides a comparative overview of common benzodiazepines, drawing data from authoritative sources to illustrate the range of potencies and durations of effect.
| 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
Understanding Onset of Action and Half-Life
The onset of action refers to how quickly you start to feel the effects of a benzodiazepine after taking it. As shown in the benzo potency chart, most benzodiazepines have a relatively rapid onset of action, typically within 15 to 30 minutes, with some like diazepam and midazolam acting even faster (0-15 minutes). This rapid onset is one reason why benzodiazepines are effective for acute anxiety or panic attacks.
Half-life is a crucial pharmacokinetic parameter that indicates how long it takes for your body to eliminate half of the drug. It’s measured in hours and is important for understanding how long a drug’s effects will last and how frequently it needs to be dosed. The benzo potency chart reveals a significant range in half-lives among different benzodiazepines, from short-acting options like midazolam (1-4 hours) and triazolam (1.6-5.5 hours) to long-acting ones like chlordiazepoxide, clorazepate, and flurazepam, which can have half-lives extending up to 100 hours. It’s important to note that half-life often includes active metabolites, meaning that even after the parent drug is metabolized, active compounds can continue to exert effects. For example, diazepam metabolizes into oxazepam, which is itself a benzodiazepine.
Comparative Oral Doses and Potency
The “Comparative Oral Dose” in the benzo potency chart is an essential concept for understanding the relative strength, or potency, of different benzodiazepines. Since there isn’t a universally standardized measure of benzodiazepine potency, these comparative doses are derived from expert sources and clinical experience. The chart includes data from two reputable sources: the Ashton Manual, a widely recognized guide for benzodiazepine withdrawal, and ClinCalc.com, a clinical decision support tool.
As highlighted in the notes below the chart, dosages can vary significantly across different benzodiazepines. A “low dose” is a relative term, and its meaning is only clarified when using a comparative scale. For instance, according to the Ashton Manual, alprazolam (Xanax) is considered approximately 20 times more potent than diazepam (Valium). Similarly, clonazepam (Klonopin) is estimated to be about 60 times more potent than temazepam (Restoril). Using data from ClinCalc, the potency ranges are slightly different but still illustrate the same principle: alprazolam is 5-20 times stronger than Valium, and clonazepam is 1.25-80 times more powerful than temazepam.
Diazepam (Valium) is often used as a reference point when comparing benzodiazepine potencies, with a comparative oral dose of 10mg. This benzo potency chart effectively demonstrates that different benzodiazepines, even within the same class, can have vastly different strengths and durations of action. This variability underscores the importance of using such charts and consulting with healthcare providers to ensure appropriate prescribing and safe use of these medications. Always consult with a healthcare professional for personalized medical advice and dosage information.
