Should diazepam (Diazepam) be administered intramuscularly (IM)?

Diazepam Should NOT Be Given Intramuscularly

Intramuscular diazepam is not recommended due to erratic and unreliable absorption, risk of tissue necrosis, and availability of superior alternatives. 1, 2

Primary Reasons to Avoid IM Diazepam

Erratic Absorption Profile

• IM diazepam absorption is slow and unpredictable, with maximum serum concentrations reached anywhere from 1 to 24 hours after injection, compared to 10-20 minutes with rectal administration 3
• The World Health Organization explicitly states that intramuscular diazepam has erratic and unreliable absorption and is not recommended as a substitute for lorazepam 2mg IM 2
• The lipophilicity of diazepam results in slow absorption from muscle tissue, making it unsuitable when rapid symptom control is required 4

Risk of Tissue Damage

• IM administration is specifically not recommended for status epilepticus because of tissue necrosis risk 1
• Pediatric emergency guidelines explicitly warn against the IM route due to potential tissue necrosis 1
• Pain at the injection site is common, with an unacceptably high incidence particularly when injected into the thigh 5

Preferred Alternative Routes

When IV Access is Available

• Administer IV diazepam (5-10mg slowly over 1 minute) or IV lorazepam 2
• IV diazepam should be given over approximately 2 minutes to avoid pain at the IV site 1
• Lorazepam is preferred over diazepam when available due to prolonged duration of anticonvulsant activity 1, 2

When IV Access is NOT Available

• Rectal diazepam should be the first choice, with bioavailability of 50% and peak levels in 10-20 minutes 3, 6
• Rectal diazepam (0.5 mg/kg up to 20 mg) provides more reliable absorption than IM administration, though absorption may be erratic 1
• If rectal administration is not possible due to medical or social reasons, IM phenobarbital is recommended as an alternative 2

Special Consideration for Midazolam

• Midazolam is the only benzodiazepine that should be given intramuscularly when parenteral non-IV administration is needed 6, 4
• Midazolam has 93-100% efficacy via the IM route, unlike diazepam 6
• When rapid control of symptoms is required and IV access is unavailable, IM midazolam should be used instead of diazepam 4

Critical Clinical Pitfall

• Do not delay treatment waiting for IM diazepam to take effect—consider alternative routes immediately 2
• The FDA label acknowledges that "if intravenous administration is impossible, the intramuscular route may be used" for status epilepticus, but emphasizes that "the intravenous route is by far preferred" 7
• This FDA statement should be interpreted as a last-resort option only, not a routine alternative 7

Context-Specific Exceptions

The FDA label does list IM administration for certain non-emergent indications (moderate anxiety, muscle spasm, endoscopic procedures) with doses of 2-10mg 7. However, even in these contexts:

• For endoscopic sedation, IV diazepam is standard, with IM given only "if intravenous cannot be used" approximately 30 minutes prior to the procedure 7
• Gastroenterology guidelines make no mention of IM diazepam for procedural sedation, focusing exclusively on IV administration 1
• For alcohol withdrawal, diazepam should be avoided when IM is the only option—use lorazepam or midazolam instead 4