Penthrox vs. Entonox for Long Term Exposure

Penthrox and Entonox are both used for pain management in healthcare – particularly in trauma or emergency settings.

In this post we’ll examine the benefits and risks of each.

What is Penthrox?

Penthrox is a disposable inhaler containing a drug called methoxyflurane. When you pour this drug into the device, a gauze inside soaks it up, allowing patients to inhale the vapours. Penthrox is mostly used to offer short-term relief from trauma pain until practitioners can establish a more long-term pain management solution.

It’s also useful for providing relief during brief, painful procedures, like wound dressing.

Penthrox inhalers weigh about 100g and are approximately 15cm long. And as they’re not pressurised, they can be transported on airplanes with no issue. As such, Penthrox is a lot more portable than other pain management solutions, which is why it’s often used in ambulances.

What is Entonox?

Entonox comes in a cannister containing 50% oxygen and 50% nitrous oxide (N₂O). Inhaling this gas mixture provides effective short-term pain relief during certain investigations and procedures.

Entonox cannisters are refillable, though they’re fitted with disposable mouthpieces that must be changed between use for better infection control. They contain built-in regulators, meaning that they can be set up and applied quickly in an emergency. All you have to do is attach a hose and a valve, and it’s ready to use.

What Are The Risks of Penthrox and Entonox?

Both Penthrox and Entonox are effective at providing pain relief. Which option you choose will depend on your budget, along with certain practical considerations, such as space and portability.

However, both Penthrox and Entonox pose certain risks, particularly when it comes to long-term exposure.

The Risks of Penthrox

Some people are hypersensitive to methoxyflurane, the drug contained in Penthrox. It can also pose risks to patients with underlying hepatic conditions, and to elderly or other patients with risk factors for renal disease.

Even small doses of Penthrox can cause dizziness, headaches, sleepiness and nausea. But excessive doses can lead to renal failure.

Maximum Dose of Penthrox

The manufacturers recommend that doses should not exceed 6ml in a day or 15ml in a week. But they also claim that “the frequency at which Penthrox can be safely used is not established”. You can read the full safety information for Penthrox on the manufacturer’s website.

The Risks of Entonox

Practitioners do not administer Entonox to patients suffering from certain conditions. For example, as Entonox can cause a rise in intracranial pressure, it’s not suitable for use with patients with head injuries. Nor should it be used if the patient has any air trapped in the body, such as with blocked bowels or restricted airways.

Short Term Exposure of Entonox

In the short-term, Entonox can cause dizziness, sleepiness, nausea, and even hallucinations. But these side effects usually stop quickly once the patient stops breathing the gas mixture.

Long Term Exposure to Entonox

Long-term exposure to Entonox can affect the body’s ability to absorb vitamin B12. This can result in damage to nerves and red blood cells.

So long as the patient uses controlled doses of Entonox only when needed, there should be no risk of any long-term effects. However, Entonox can pose an occupational risk to healthcare workers. Cannisters can leak, and some of the gas mixture may escape through the patient’s mouthpiece.

Risk to Hospital Staff

Entonox is often used in maternity wards to provide pain relief during labour. There have long been concerns about midwives’ occupational exposure to Entonox, and the long-term health risks this may pose.

How to Manage Penthrox and Entonox Risks In Your Hospital

When it comes to Penthrox, the manufacturers recommend that patients self-administer using an Activated Carbon (AC) Chamber, and that they always exhale through the inhaler’s mouthpiece. Yet even with these measures in place, some methoxyflurane may still escape, posing occupational risks to practitioners.

Similarly, you can reduce the occupational risks of Entonox through carefully controlling dosages, and through advising patients on safe and effective use. Though if patients are self-administering Entonox, they’ll be doing so while in a state of acute pain and stress. So it’s almost inevitable that some potentially-harmful N₂O may leak and circulate.

Test Staff Exposure Levels

So if you want to significantly reduce the occupational risks of Penthrox and Entonox, it’s best to test your staff’s exposure levels before establishing a reliable air purification system.

We specialise in exposure monitoring for healthcare settings. Using both continuous monitoring and personal sampling techniques, we’ll produce a comprehensive workplace exposure monitoring report for any hazardous substances in your hospital, including methoxyflurane and N₂O.

Get in touch to discuss how we can help you control the occupational risks in your healthcare setting.