No, Xanax (alprazolam) 0.5 mg is NOT the same as lorazepam 0.5 mg or clonazepam 0.5 mg
These are three distinct benzodiazepines with different potencies, and 0.5 mg doses are not equivalent. First, let me clarify the terminology: Xanax is the brand name for alprazolam, not lorazepam. These are separate medications.
Benzodiazepine Equivalency
The three benzodiazepines in question have different potencies:
- Alprazolam (Xanax) 0.5 mg is approximately equivalent to lorazepam 1 mg 1
- Clonazepam 0.5 mg is roughly equivalent to alprazolam 0.5 mg or lorazepam 1 mg
This means that lorazepam 0.5 mg is approximately half the potency of alprazolam 0.5 mg or clonazepam 0.5 mg.
Key Pharmacological Differences
Duration of Action
These medications differ substantially in how long they work:
- Alprazolam: Intermediate-acting with a half-life of approximately 11.2 hours (range 6.3-26.9 hours) 2
- Lorazepam: Short to intermediate-acting, typically dosed every 2-6 hours for acute management 3
- Clonazepam: Longer-acting than both alprazolam and lorazepam 4
Research demonstrates that clonazepam and lorazepam impair neuromotor performance for 2-4 hours longer than alprazolam at equivalent doses 4.
Clinical Applications
Guidelines suggest different uses based on their pharmacological profiles 1:
- Alprazolam: Primarily for generalized anxiety and panic disorder; fast onset of symptom relief
- Lorazepam: Preferred for acute agitation, delirium management (starting dose 0.25-0.5 mg in elderly), and status epilepticus 3, 5
- Clonazepam: Often used for panic disorder and may be considered when longer duration of action is appropriate 1
Cognitive Effects
At therapeutic doses, all three produce similar cognitive impairment patterns, though the duration differs:
- Alprazolam 0.5 mg primarily affects visual attention (large effect size d=0.8) 6
- Lorazepam and alprazolam show no significant difference in anterograde memory impairment at equivalent doses 7
- Higher doses (alprazolam 1 mg) additionally impair working memory and learning 6
Clinical Implications
When switching between these medications, you cannot simply use the same milligram dose. The approximate equivalent conversions are:
- Alprazolam 0.5 mg ≈ Lorazepam 1 mg ≈ Clonazepam 0.5 mg
Important Caveats
- Individual variation: Drug levels can vary considerably for a given dose, particularly with alprazolam 8
- Age considerations: Elderly patients show 25-50% higher concentrations and longer half-lives, requiring dose reduction 2
- Hepatic impairment: Alprazolam half-life increases to 19.7 hours in liver disease 2
- Withdrawal risk: All three carry risk of dependence; alprazolam requires careful tapering at discontinuation 2
The bottom line: These are not interchangeable at the same dose. If you're considering switching between these medications, use appropriate equivalency ratios and account for differences in duration of action and individual patient factors.