What intravenous dose of lorazepam is equivalent to a 1 mg oral dose of lorazepam (Ativan)?

Medical Advisory Board
All articles are reviewed for accuracy by our Medical Advisory Board.

Educational purpose only · Not a substitute for professional judgment or the full text of guidelines and labels.

Article Review Status

Submitted

Under Review

Approved

Last updated: April 10, 2026 · View editorial policy

The FDA labeling for oral lorazepam does not provide a direct mg-for-mg IV conversion for “1 mg PO = ___ mg IV.” [1]

Using pharmacokinetic exposure to estimate an equivalent IV dose:

Oral lorazepam has absolute bioavailability ~90%. [1]
An oral 1 mg dose delivers ~0.9 mg systemic exposure (1 mg × 0.90). [1]
IV bioavailability is ~100% by definition for systemic exposure comparison, so the approximate IV dose for the same exposure is 0.9 mg ÷ 1.0 = 0.9 mg? (equivalently 1.0 mg ÷ 0.90 = 1.1 mg when solving for IV dose that matches oral delivered exposure).

Estimated IV equivalent dose: ~1.1 mg IV lorazepam for 1 mg oral lorazepam (systemic exposure equivalence based on 90% oral bioavailability). [1]

Sources (1)