Can lorazepam be administered intravenously diluted in 100 mL of normal saline for an acute anxiety attack?

Can Lorazepam Be Given in 100mL Normal Saline for Anxiety Attack?

Yes, lorazepam can be diluted in normal saline for intravenous administration to treat acute anxiety, but the FDA-approved dilution is 1:1 (equal volume), not 100mL. For an anxiety attack, the standard approach is to dilute lorazepam injection with an equal volume of compatible solution immediately prior to IV use, then inject slowly at no more than 2 mg per minute 1.

FDA-Approved Dilution and Administration

The FDA label is explicit about proper dilution technique 1:

• Immediately prior to IV use, lorazepam injection must be diluted with an equal volume of compatible solution (Sterile Water for Injection, Sodium Chloride Injection, or 5% Dextrose Injection)
• Mix thoroughly by gently inverting the container repeatedly until homogenous—do not shake vigorously
• When properly diluted, inject directly into a vein or into the tubing of an existing IV infusion
• Rate of injection should not exceed 2 mg per minute

Dosing for Acute Anxiety

For sedation and relief of anxiety, the FDA-approved dose is 1:

• Initial dose: 2 mg total, or 0.02 mg/lb (0.044 mg/kg), whichever is smaller
• This dose should not be exceeded in patients over 50 years of age
• In patients requiring greater anxiolysis, doses up to 0.05 mg/kg (maximum 4 mg total) may be administered

The 2020 NICE COVID-19 guidelines for managing anxiety in the community recommend lorazepam 0.5-1 mg orally four times daily as needed (maximum 4 mg in 24 hours), with reduced doses of 0.25-0.5 mg in elderly or debilitated patients 2. For patients unable to swallow, midazolam subcutaneously is preferred over IV lorazepam 2.

Why Not 100mL?

Diluting lorazepam in 100mL normal saline is not standard practice and creates several problems:

1. Stability concerns: Lorazepam in normal saline is physically and chemically unstable, with precipitation and >10% concentration loss occurring within 2-4 days even under optimal storage conditions 3. Larger dilution volumes may accelerate this instability.

2. Propylene glycol toxicity risk: The parenteral formulation contains propylene glycol as a diluent, which can cause metabolic acidosis and acute kidney injury. While initially thought to occur only with high-dose continuous infusions, toxicity can occur with total daily IV doses as low as 1 mg/kg 4. Diluting in larger volumes doesn't eliminate this risk and may complicate monitoring.

3. Infusion rate control: The FDA mandates injection rates not exceeding 2 mg/min to avoid pain at the IV site and respiratory depression 1. A 100mL bag would require careful rate calculation and monitoring, increasing the risk of administration errors.

Clinical Evidence for IV Lorazepam in Acute Anxiety

The evidence base for IV lorazepam in acute anxiety is limited but supportive:

• A 1975 double-blind trial showed 85% of patients were free of anxiety symptoms after 3 mg IV lorazepam versus 11.8% with placebo, with effects discernible within 10 minutes 5
• A 1978 study of 115 patients with acute anxiety crises found complete symptom abolition or reasonable control within 30 minutes in all but 2 patients using 3 mg IV lorazepam 6
• A 2021 systematic review confirmed lorazepam's clinical effectiveness for acute agitation, though most studies used IM rather than IV routes 7

Practical Approach for Acute Anxiety Attack

For an acute anxiety attack requiring IV treatment:

1. Prepare the dose: Draw up 2 mg lorazepam injection (or appropriate weight-based dose)
2. Dilute 1:1: Add an equal volume of normal saline (e.g., 2 mL lorazepam + 2 mL NS)
3. Mix gently: Invert repeatedly—do not shake vigorously
4. Administer slowly: Inject at ≤2 mg/min directly into vein or into IV tubing
5. Monitor closely: Watch for respiratory depression, especially if combined with other sedatives

For less acute situations, oral or sublingual lorazepam is preferred (0.5-1 mg), as sublingual absorption is complete and comparable to IV administration 8.

Critical Safety Considerations

• Respiratory depression risk: Increased when combined with other CNS depressants, particularly opioids 4, 1. Be prepared to support ventilation.
• Hypotension: Can occur, especially in patients with baseline cardiovascular instability 1
• Paradoxical agitation: May occur, especially in younger children 9
• Elderly patients: Use lower doses (0.25-0.5 mg) due to increased sensitivity 2, 4

The combination of lorazepam with haloperidol is superior to either agent alone for severe agitation, but lorazepam alone is less likely to cause extrapyramidal side effects compared to antipsychotics 7, 10.