Diphenhydramine Intravenous for Adults

Who can administer

May be administered by registered competent doctor or nurse/midwife

Important information

• Unlicensed medication
• Intended use is for (primarily) Haem/Onc patients experiencing a hypersensitivity reaction who require an IV antihistamine whilst chlorphenamine IV is temporarily unavailable (product shortage)

Available preparations

Diphenhydramine Hydrochloride injection, USP 50mg /1 ml (Hikma Pharmaceuticals USA Inc.) 

Reconstitution

Already in solution

Infusion fluids

Sodium chloride 0.9%

Methods of intravenous administration

Slow intravenous injection (treatment of a hypersensitivity reaction)

• Can dilute with Sodium chloride 0.9% to produce a suitable volume
• Administer at a maximum rate of 25mg per minute

Intermittent intravenous infusion (prevention of hypersensitivity reactions)

• Add required dose to  50mL infusion fluid and administer over 15 minutes (ref 1)

Dose in adults

Usual dose

• Give 10 to 50mg at a rate generally not exceeding 25mg per minute
• Maximum daily dose is 400mg

Monitoring

• May cause drowsiness and has an additive effect with alcohol 
• More likely to cause dizziness, sedation and hypotension in elderly patients

Storage

Protect from light - keep covered in carton until time of use 

Store at 20-25⁰C, excursions permitted to 15-30⁰C

References

SPC: Diphenhydramine Hydrochloride injection, USP 50mg/ml (Hikma Pharmaceuticals USA Inc.)

1. BCCA reference attached (management of infusion related reactions)

Therapeutic classification

Antihistamine