MDR Rule 20: Why Inhalation Devices Default to IIa, Not Class I

Annex VIII, Chapter III of EU MDR added a rule the old directive's Annex IX never had: Rule 20, for devices that administer a medicinal product by inhalation. Under the Medical Devices Directive, many non-active inhalation devices were worked through the general invasive-device rules and landed, more often than not, at Class I — self-certified, no Notified Body in sight. Rule 20 ends that. The device is now classified at Class IIa by default, with a hazard test on the medicinal product itself deciding whether it climbs to IIb. Devices that used to self-certify now carry a Notified Body review, and more than one manufacturer has found that out at CE-marking renewal rather than before it.

What changed from the old directive

Under Directive 93/42/EEC, Annex IX had no rule written for inhalation. A non-active inhalation device, absent any other trigger, was typically worked through the general rules for invasive devices with respect to body orifices and landed at Class I — a manufacturer self-declaration with no Notified Body review. MDR Annex VIII, Chapter III closed that gap. Rule 20 is one of four special rules — 19, 20, 21, and 22 — that Annex VIII added and the old directive never had. Reconciling it to your wider inhalation and nasal drug-device strategy is what keeps a reclassification from becoming a certificate-renewal emergency rather than a planned project.

The hazard test that decides IIa or IIb

Rule 20 does not branch on the device's mechanism, its reusability, or how it is held. It branches on the medicinal product it administers. A device intended to administer a medicinal product by inhalation through a body orifice, without being surgically invasive, is Class IIa by default — unless the manner in which it operates is potentially hazardous considering the nature, the concentration, and the site of application of that medicinal product, in which case it is Class IIb. That means the same physical inhaler platform can sit at two different classes depending on which drug it delivers.

• Nature of the medicinal product. A device delivering a potent, narrow-therapeutic-index, or systemically active compound carries a different hazard profile than one delivering a topically acting bronchodilator.
• Concentration. The same device design can cross from IIa to IIb purely because a higher-concentration formulation changes what happens if dosing goes wrong.
• Site of application. Deep lung deposition versus upper-airway or nasal deposition changes the hazard the device's manner of operation presents.
• Manner of operation. Metering accuracy, failure modes, and how forgiving the device is of misuse feed directly into whether the combination reads as potentially hazardous.

Rule 20 doesn't ask what the device is. It asks what happens if the device's manner of operation goes wrong with this medicinal product, at this concentration, at this site of application. Why the same inhaler platform can sit at two different classes

Not the same question as Article 117

Rule 20 is easy to conflate with the separate Article 117 question. Rule 20 governs devices placed on the market as devices in their own right — a reusable inhaler platform, a nebulizer sold separately, a nasal device intended for use with more than one product. A device permanently integrated with a single named medicinal product, so that the combination is itself regulated as the medicinal product, instead goes through Article 117: the device constituent is assessed against the MDR's general safety and performance requirements through a notified body opinion folded into the marketing authorisation dossier, not classified and CE-marked on its own. Teams building a combination-product strategy need both tracks mapped before CE-marking or marketing-authorisation planning starts, not discovered midway through one.

1. Confirm the placement route first. Standalone device under Rule 20, or integral combination product under Article 117 — the two tracks require different dossiers and different reviewers.
2. Separately, confirm device status. The device-versus-medicinal-product borderline question under MDCG 2022-5 is a different determination again, and has to be settled before either Rule 20 or Article 117 applies.
3. Run the hazard test last. Only once placement and device status are both settled does the nature, concentration, and site-of-application analysis decide IIa or IIb.

Where this quietly bites

The failure mode is rarely a team ignoring Rule 20 outright. It's a legacy MDD Class I inhalation device whose technical file was never re-opened against the new rule, because nothing about the device itself changed. A dry powder inhaler platform, a nebulizer accessory, a nasal spray pump — each can carry a self-declaration that predates MDR and was simply carried forward at CE-marking transition, without anyone running the Rule 20 hazard test against the product it actually delivers. As with the same special-rule pattern Rule 21 set for substance-based devices, the risk isn't that the rule is obscure — it's that a device already on the market never gets flagged back to a classification file that now has to answer a question the old directive didn't ask.

None of this is exotic once the two questions are separated: which track the product is on, and what the hazard test says about the device-and-drug pairing it is now classified against. What makes Rule 20 dangerous is treating an inhalation device's classification as settled because it has always been Class I, rather than as a hazard argument that has to survive a Notified Body reading it cold. If your inhalation or nasal portfolio's classification predates a fresh Rule 20 review, that is where to start; our EU MDR device classification work exists for exactly this gap.