What is the onset of action for oral lorazepam (Ativan)?

From the Guidelines

Oral lorazepam typically takes effect within 15-30 minutes after ingestion, with peak effects occurring around 1-2 hours after administration. The onset of action depends on several factors including whether it's taken on an empty stomach (faster absorption) or with food (slower absorption) 1.

Key Considerations

• The standard dose ranges from 0.5 mg to 2 mg, with effects lasting approximately 6-8 hours for most people.
• If you're taking lorazepam for anxiety, you may notice initial calming effects within the first 30 minutes, while full therapeutic effects for sleep may take up to an hour.
• Lorazepam works by enhancing the effects of gamma-aminobutyric acid (GABA), a neurotransmitter that inhibits brain activity, resulting in sedative, anxiolytic, and muscle relaxant effects.

Important Safety Information

• Be aware that lorazepam is a benzodiazepine with potential for dependence, so it should only be used as prescribed and typically for short-term treatment.
• Never combine it with alcohol or other central nervous system depressants as this can cause dangerous respiratory depression.

Dosage and Administration

• According to the guidelines, lorazepam 0.5-1 mg orally four times a day as required (maximum 4 mg in 24 hours) can be used for anxiety or agitation in patients who are able to swallow 1.
• The dose should be reduced to 0.25-0.5 mg in elderly or debilitated patients (maximum 2 mg in 24 hours) 1.

From the Research

Onset of Action

• The onset of action of oral lorazepam can occur within 30-60 minutes, with peak effects reached at around 60-90 minutes 2.
• One study found that the latency of peak action for lorazepam was about 60-90 minutes, with a duration of effect lasting more than 240 minutes 2.
• The time course of antirecall effect and grades of sedation after oral administration of lorazepam were determined in 120 patients, with results showing a latency of 30-60 minutes and a duration of more than 240 minutes 2.

Pharmacokinetics

• Lorazepam is rapidly and readily absorbed, reaching peak concentrations in the blood proportional to the dose approximately 2 hours after oral administration 3.
• The elimination half-life of lorazepam is about 12 hours, with 70-75% of the administered dose excreted as the glucuronide conjugate in the urine 3.
• Steady state blood levels of lorazepam occur within 2-3 days and are maintained after several months of continuous treatment 3.

Clinical Considerations

• Benzodiazepines, including lorazepam, are commonly prescribed for their sedative effects, but they can have debilitating side effects, including addictive potential and withdrawal symptoms 4.
• The use of benzodiazepines, including lorazepam, should be carefully considered and monitored due to their potential for dependence and withdrawal symptoms 4.