Alprazolam (Xanax) Equivalence to Other Benzodiazepines
Alprazolam 0.5 mg is approximately equivalent to 10 mg of diazepam (Valium) in terms of clinical potency. 1, 2
Benzodiazepine Equivalence
Benzodiazepines differ in their potency, onset of action, and duration of effect. When comparing alprazolam (Xanax) to diazepam (Valium), the following equivalence can be established:
- Alprazolam is approximately 10 times more potent than diazepam, making 0.5 mg of alprazolam roughly equivalent to 10 mg of diazepam 3
- Alprazolam has a faster onset of action (peak plasma levels reached in 0.7-2.1 hours) compared to some other benzodiazepines 4
- Alprazolam has an intermediate half-life of 12-15 hours, whereas diazepam has a longer half-life (20-120 hours) 5, 4
Pharmacokinetic Differences
The clinical differences between alprazolam and diazepam are important to consider:
- Alprazolam is rapidly absorbed with over 90% bioavailability after oral administration 1
- Diazepam has more erratic absorption, especially when administered intramuscularly 5
- Alprazolam reaches peak serum concentrations faster than many other benzodiazepines 4
- Diazepam has active metabolites that can prolong its clinical effects, especially in patients with renal dysfunction 5
Clinical Considerations
When substituting between benzodiazepines, consider these important factors:
- Alprazolam may have a more severe withdrawal syndrome than diazepam due to its shorter half-life 6
- Diazepam's longer half-life may make it more suitable for patients who need longer duration of action 5, 2
- Alprazolam has been associated with greater reinforcing properties and potentially higher addiction potential 6
- Both medications can cause respiratory depression, especially when combined with other CNS depressants 5
Benzodiazepine Comparison Table
| Benzodiazepine | Equivalent Dose | Onset of Action | Duration of Effect |
|---|---|---|---|
| Alprazolam (Xanax) | 0.5 mg | 1-2 min | 12-15 hours |
| Diazepam (Valium) | 10 mg | 2-5 min | 20-120 hours |
| Lorazepam (Ativan) | 2 mg | 15-20 min | 8-15 hours |
| Temazepam (Restoril) | 15-30 mg | Variable | Short-intermediate |
Common Pitfalls in Benzodiazepine Substitution
- Failing to account for differences in potency can lead to under or overdosing 3
- Not considering the patient's hepatic and renal function when switching between benzodiazepines 5
- Overlooking the potential for more severe withdrawal symptoms when switching from longer-acting to shorter-acting benzodiazepines 6
- Ignoring drug interactions that may affect benzodiazepine metabolism (e.g., cimetidine and oral contraceptives can reduce alprazolam clearance) 1
Remember that benzodiazepines should be used at the lowest effective dose for the shortest duration possible to minimize the risk of dependence and adverse effects 5.