What is the equivalent dose of lorazepam (Ativan) for 1 mg of alprazolam (Xanax) every 4 hours?

Benzodiazepine Dose Conversion: Alprazolam to Lorazepam

For a patient taking 1 mg of alprazolam (Xanax) every 4 hours (6 mg/day total), the equivalent lorazepam (Ativan) dose is 2 mg every 4 hours (12 mg/day total), using a 1:2 conversion ratio.

Conversion Ratio and Calculation

• The standard conversion ratio is 1 mg alprazolam = 2 mg lorazepam 1, 2
• Your patient is taking 1 mg alprazolam every 4 hours = 6 doses per day = 6 mg/day total alprazolam
• Converting to lorazepam: 6 mg alprazolam × 2 = 12 mg lorazepam per day
• Divided into the same dosing schedule: 2 mg lorazepam every 4 hours (6 doses daily)

Evidence Supporting This Conversion

• A double-blind comparative study demonstrated that alprazolam doses averaging 1.59 mg/day were clinically equivalent to lorazepam doses averaging 5.97 mg/day, supporting an approximate 1:4 ratio 1
• However, the more conservative and widely accepted conversion in clinical practice is 1:2 (alprazolam:lorazepam), which accounts for differences in potency while maintaining safety 2
• Research on steady-state dose equivalences confirms that when converting between benzodiazepines with different half-lives, the accumulation ratios must be considered, and lorazepam's intermediate half-life (10-20 hours) versus alprazolam's shorter half-life (11-16 hours) supports the 1:2 conversion 2

Critical Clinical Considerations

Dosing frequency matters significantly:

• Alprazolam every 4 hours (6 times daily) is an unusually frequent dosing schedule, suggesting either very high anxiety or possible tolerance/dependence 3
• Lorazepam's longer duration of action may allow for less frequent dosing (every 6-8 hours rather than every 4 hours) once stabilized, potentially reducing total daily dose requirements 4, 5

Important caveats when making this conversion:

• Do not abruptly switch—consider a gradual substitution over 24-48 hours, giving both medications initially and tapering the alprazolam while increasing lorazepam 6
• Monitor closely for breakthrough withdrawal symptoms during the first 48-72 hours, as incomplete cross-tolerance can occur despite theoretical equivalence 6
• The very frequent dosing pattern (every 4 hours) suggests this patient may have developed tolerance or dependence, and 47% of long-term benzodiazepine users have concurrent anxiety disorders requiring ongoing treatment 3
• Elderly or debilitated patients should receive reduced doses (start with 1 mg lorazepam every 4-6 hours instead of 2 mg) due to increased sensitivity 7

Practical Conversion Algorithm

1. Calculate total daily alprazolam dose: 1 mg × 6 doses = 6 mg/day
2. Apply 1:2 conversion ratio: 6 mg × 2 = 12 mg lorazepam/day
3. Maintain initial dosing frequency: 12 mg ÷ 6 doses = 2 mg every 4 hours
4. After 48 hours of stability, consider transitioning to every 6-hour dosing (2 mg four times daily = 8 mg/day) to leverage lorazepam's longer half-life 4, 5
5. Monitor for oversedation (lorazepam causes less venous irritation but similar CNS depression) 8

Common Pitfalls to Avoid

• Avoid using a 1:1 conversion ratio—this will result in significant underdosing and withdrawal symptoms 1, 2
• Do not assume perfect cross-tolerance—some patients experience withdrawal symptoms despite adequate theoretical dose conversion, requiring additional as-needed doses during transition 6
• Watch for respiratory depression, especially if the patient takes other CNS depressants 9, 7
• Paradoxical agitation occurs in approximately 10% of patients on lorazepam 7