Naloxone 400mcg Injection (0.4mg/mL)

Naloxone 400mcg Injection contains 0.4mg naloxone hydrochloride in 1mL and is a prescription opioid antagonist used for the reversal of opioid-induced respiratory and central nervous system depression. Current U.S. products include 1mL single-dose vials, while UK products are marketed as 400 micrograms/mL solution for injection or infusion.

Product Information

• Generic Name: Naloxone Hydrochloride
• Strength: 400mcg/1mL
• Equivalent Concentration: 0.4mg/mL
• Drug Class: Opioid Antagonist
• Dosage Form: Sterile Injection / Injection-Infusion Solution
• Route: IV, IM or SC, depending on product labeling
• Prescription: Yes for the referenced injection products
• Common Presentation: 1mL single-dose vial or ampoule
• Primary Use: Reversal of opioid-induced respiratory and CNS depression

Main Uses

Naloxone is used for the complete or partial reversal of opioid-induced respiratory and central nervous system depression and may also be used in the assessment of suspected acute opioid overdose.

How It Works

Naloxone is an opioid antagonist that competitively counteracts opioid effects. Its clinical purpose is to restore opioid-inhibited functions such as respiration when opioid toxicity or excessive opioid effect is present.

Strength Clarification

400mcg = 0.4mg. A standard 1mL presentation contains 400mcg total naloxone at a concentration of 400mcg/mL (0.4mg/mL). It should not be described as a 400mg injection.

Availability & Ordering

Commercial search terms include Naloxone 400mcg Injection, Naloxone 0.4mg/mL Injection, Naloxone Hydrochloride 400mcg, Naloxone 400 micrograms/mL, Naloxone 0.4mg Injection and Naloxone injection price. India currently has 400mcg naloxone injection products such as Nalox 400mcg Injection and Nex 400mcg Injection, while Australia markets Narcan Injection at 400mcg in 1mL.

Safety Information

Naloxone can precipitate acute opioid withdrawal in opioid-dependent patients. Reversal of opioid effects may be temporary, so patients require appropriate clinical observation and further management when necessary. Product-specific administration and monitoring instructions must be followed.

Frequently Asked Questions

What is Naloxone 400mcg Injection used for?

It is used to reverse opioid-induced respiratory and central nervous system depression, including in suspected opioid overdose.

Is 400mcg the same as 0.4mg?

Yes. 400mcg equals 0.4mg.

Is Naloxone 400mcg the same as Naloxone 0.4mg/mL?

A 1mL product containing 400mcg has a concentration of 0.4mg/mL. Total amount and concentration should still be stated separately on the product page.

What is the usual 400mcg presentation?

A commonly documented presentation is 1mL containing 400mcg (0.4mg) naloxone hydrochloride.

Is Naloxone 400mcg Injection the same as Narcan®?

Narcan® is a brand name used for naloxone products in some markets. A generic naloxone injection contains the active ingredient naloxone hydrochloride but may differ in manufacturer, packaging and formulation details. Australia’s Phebra currently markets Narcan Injection at 400mcg/1mL.

Can Naloxone Injection be used for general pain?

No. Naloxone is used to reverse opioid effects; it is not a painkiller.

Last Updated: September 29, 2026

Medical Disclaimer: This information is for educational and product-reference purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Naloxone injection should be administered according to the prescribing information for the exact product.