Rules 14 to 22 in Annex VIII of Regulation (EU) 2017/745 are the special classification rules. They sit after the non-invasive, invasive, and active families, and they exist because certain device categories. Drug-device combinations, contraceptives, disinfectants, diagnostic X-ray recording media, tissue-derived devices, nanomaterial devices, inhalation route devices, substance-based devices that are absorbed by the body, and active therapeutic devices with an integrated diagnostic function. Carry risks the earlier rules do not handle cleanly. Each of these rules can produce a class up to Class III in its own right, and each one must be checked for every device regardless of which "main" rule already applied. The authoritative interpretation guide is MDCG 2021-24 (October 2021), and the Borderline Manual v4 (September 2025) records case-by-case precedent.

By Tibor Zechmeister and Felix Lenhard. Last updated 10 April 2026.

TL;DR

  • Annex VIII Rules 14 to 22 of Regulation (EU) 2017/745 are the nine special classification rules. They are not a fallback group. They apply in parallel with Rules 1 to 13, and when more than one rule catches a device, the highest class wins under the Section 2 implementing rules.
  • Rule 14 handles devices incorporating a medicinal substance in an ancillary role. Rule 15 handles contraception and prevention of sexually transmitted diseases. Rule 16 handles disinfection, cleaning, rinsing, and hydrating of contact lenses, and disinfecting or sterilising other medical devices. Rule 17 handles devices specifically intended for recording of diagnostic images generated by X-ray radiation.
  • Rule 18 handles devices made using non-viable tissues or cells of human or animal origin or their derivatives. Rule 19 handles devices incorporating or consisting of nanomaterial. Rule 20 handles invasive devices with respect to body orifices that administer medicinal products by inhalation.
  • Rule 21 handles devices composed of substances or combinations of substances that are absorbed by the body or locally dispersed. Rule 22 handles active therapeutic devices with an integrated or incorporated diagnostic function that significantly determines patient management. Closed-loop systems and automated external defibrillators are the textbook examples.
  • Classification is the manufacturer's responsibility under MDR Article 51. Every classification decision must cite the specific rule and the specific intended purpose under Article 2(12). MDCG 2021-24 is the interpretation guide. The Borderline Manual v4 is the precedent register.

Why these rules get skipped. And why that is expensive

Founders who work through Annex VIII in order tend to land somewhere in Rules 1 to 13, write down the class, and stop. The special rules get treated as footnotes. The result is a classification that is defensible against the rule the founder looked at, and indefensible against the one the Notified Body looked at. Rule 19 on nanomaterial catches more advanced-material devices than expected. Rule 21 catches a growing category of substance-based products. Rule 22 catches any closed-loop therapeutic system, which is most of the interesting active-device innovation right now. None of these are obscure. All of them are missed regularly.

The fix is procedural. After landing on a rule in the non-invasive, invasive, or active family, walk through Rules 14 to 22 as a second pass. Ask, for each one, whether the intended purpose of the device could bring it within scope. If yes, note the class the special rule produces. Compare against the class from the first pass. The higher one governs. This is the Section 2 implementing rule at work. The strictest rule and sub-rule producing the higher classification applies. And there is no way around it.

This post walks through each of the nine special rules in turn. For each, it states the scope, lists the typical devices, and flags the traps. For a full rule-by-rule walk that also covers Rules 1 to 13, see the complete guide to MDR Annex VIII classification rules.

Rule 14. Devices incorporating a medicinal product with ancillary action

Scope. Rule 14 covers devices that incorporate, as an integral part, a substance which, if used separately, would be considered a medicinal product, and where the action of that substance is ancillary to that of the device. These are Class III.

Typical devices. Drug-eluting stents where the stent itself is the principal mode of action and the drug coating is ancillary. Heparin-coated catheters. Bone cements with antibiotic loading. Surgical meshes with an antimicrobial coating where the mesh is the primary device.

The trap. The ancillary question is not about quantity or cost. It is about mode of action. If the substance is doing the principal work, the product is a medicinal product regulated under the pharmaceutical framework, not a medical device under the MDR. If the device is doing the principal work and the substance supports it, Rule 14 applies and the class is III. The borderline determination requires documented analysis of the intended purpose and mode of action, and this is exactly the kind of case where the Borderline Manual v4 (September 2025) precedent register is worth consulting before filing.

Rule 15. Contraception and prevention of sexually transmitted diseases

Scope. Rule 15 covers devices used for contraception or prevention of the transmission of sexually transmitted diseases. These are Class IIb, unless they are implantable or long-term invasive devices, in which case they are Class III.

Typical devices. Condoms. Diaphragms. Intrauterine devices (IUDs). Which, being long-term invasive, sit at Class III. Implantable contraceptive systems. Class III by the same logic.

The trap. Non-hormonal IUDs are medical devices under the MDR. Hormonal IUDs fall under the medicinal-products framework because the hormone is the principal mode of action. Which puts them outside the MDR entirely or inside it under Rule 14 depending on the specifics. Getting the borderline right before classifying is critical. Short-term vs. long-term invasive is determined by the Annex VIII duration definitions, not by calendar intuition, and those definitions matter for whether Rule 15 produces IIb or III.

Rule 16. Disinfection, cleaning, rinsing, and contact lens care

Scope. Rule 16 covers two distinct categories. First, devices specifically intended for disinfecting, cleaning, rinsing, or where appropriate hydrating contact lenses. These are Class IIb. Second, devices specifically intended for disinfecting or sterilising medical devices. These are Class IIa by default, but escalate to Class IIb for devices specifically intended to be used for the disinfection of invasive devices, and the washer-disinfector and sterilisation end of this group lands in Class IIb in practice.

Typical devices. Contact lens solutions, saline rinsing systems, and hydrogen-peroxide-based lens disinfection kits on the contact lens side. On the medical device processing side: endoscope washer-disinfectors, steam sterilisers for reusable instruments, chemical sterilants for reusable surgical devices.

The trap. Founders building accessories for reusable devices often forget that the cleaning and disinfection aids themselves are medical devices in their own right and get their own classification under Rule 16. A simple reprocessing brush marketed with disinfection claims can pull in obligations that a plain brush would not.

Rule 17. Devices for recording diagnostic X-ray images

Scope. Rule 17 covers devices specifically intended for the recording of diagnostic images generated by X-ray radiation. These are Class IIa.

Typical devices. Digital X-ray detectors. Computed radiography image plates. The physical recording medium whose fidelity determines the diagnostic quality of the image sits here.

The trap. Rule 17 is narrow. It applies to the recording medium itself, not to the X-ray source (which sits under Rule 10 as an active device emitting ionising radiation for diagnostic interventional radiology, typically Class IIb) and not to the software that post-processes the image (which sits under Rule 11). A system-level product can hit Rule 17 on the detector, Rule 10 on the source, and Rule 11 on the software simultaneously. The highest class wins, but each sub-assembly still has to be justified against its own rule.

Rule 18. Devices using non-viable tissues or cells of human or animal origin

Scope. Rule 18 covers devices manufactured utilising tissues or cells of human or animal origin, or their derivatives, which are non-viable or rendered non-viable. These are Class III. With a narrow exception. Where such devices are manufactured using tissues or cells of animal origin, or their derivatives, which are non-viable or rendered non-viable, and which are intended to come into contact with intact skin only, they are Class I.

Typical devices. Collagen wound dressings derived from animal tissue. Bioprosthetic heart valves made from porcine or bovine tissue (Class III under Rule 18 and separately caught by Rule 8). Bone grafting materials derived from animal bone. Dermal fillers derived from animal collagen where the intended purpose brings them into the medical device scope.

The trap. The human-origin and animal-origin branches are treated differently, and the "intact skin only" exception is very narrow. Any device that contacts mucous membrane, injured skin, or any deeper tissue loses the exception and lands at Class III. Human-origin tissue devices also interact with the separate regulatory framework for tissues and cells of human origin. The borderline between the MDR and that framework is a frequent trap.

Rule 19. Devices incorporating or consisting of nanomaterial

Scope. Rule 19 covers devices incorporating or consisting of nanomaterial. The class depends on the potential for internal exposure: Class III if the device presents a high or medium potential for internal exposure; Class IIb if it presents a low potential for internal exposure; Class IIa if it presents a negligible potential for internal exposure.

Typical devices. Devices with nano-coatings for antimicrobial or bio-integration purposes. Advanced dental restorative materials with nanoparticle fillers. Drug delivery systems using nanoparticle carriers. Imaging contrast agents using nanoparticles (where they qualify as devices rather than medicinal products).

The trap. Rule 19 catches more devices than founders expect because the definition of nanomaterial in the MDR is broad and because "potential for internal exposure" is a risk-based assessment, not a binary. A device that only releases nanomaterial under certain use conditions still has to be assessed. Getting the exposure tier wrong moves a product between IIa, IIb, and III. All three are possible outcomes for what looks like the same device. This is exactly the kind of judgment call where MDCG 2021-24 worked examples and Notified Body pre-submission dialogue pay for themselves.

Rule 20. Devices administering medicinal products by inhalation

Scope. Rule 20 covers invasive devices with respect to body orifices (other than surgically invasive devices) that are intended to administer medicinal products by inhalation. These are Class IIa, escalating to Class IIb if their mode of action has an essential impact on the efficacy and safety of the administered medicinal product, or if they are intended to treat life-threatening conditions.

Typical devices. Dry powder inhalers. Metered-dose inhaler spacers and actuators. Nebuliser mouthpieces and masks when sold as medical devices. Any inhalation delivery hardware where the device controls dose, particle size, or timing.

The trap. The IIa-to-IIb escalation depends on whether the device has an "essential impact" on the medicine's efficacy and safety. For a simple pass-through spacer, arguably no. For a breath-actuated dose-counting inhaler that controls particle size distribution, clearly yes. The distinction is documented in the intended purpose and the engineering claims, and the class follows the documentation. Not the other way around. If the marketing material talks about precision dosing and the technical file does not, the Notified Body will ask about the gap.

Rule 21. Substance-based devices absorbed or locally dispersed

Scope. Rule 21 covers devices that are composed of substances or combinations of substances intended to be introduced into the human body via a body orifice or applied to the skin, and that are absorbed by or locally dispersed in the human body. The class depends on the route and the degree of systemic absorption:

  • Class III if they, or their products of metabolism, are systemically absorbed by the human body in order to achieve the intended purpose.
  • Class III if they achieve their intended purpose in the stomach or lower gastrointestinal tract and they, or their products of metabolism, are systemically absorbed by the human body.
  • Class IIa if they are applied to the skin, or if they are applied in the nasal or oral cavity as far as the pharynx, and achieve their intended purpose on those cavities.
  • Class IIb in all other cases.

Typical devices. Nasal decongestant sprays that act as devices rather than medicinal products. Oral rinses with a physical mode of action. Topical barrier products. Certain laxatives and anti-reflux products where the mode of action is physical (osmotic, bulk-forming, barrier) rather than pharmacological.

The trap. Rule 21 sits at the border with the medicinal-products framework. If the mode of action is pharmacological, immunological, or metabolic, the product is a medicinal product, not a device, regardless of Rule 21. Getting onto the device side of the border requires documented evidence of a physical mode of action. Once the product is confirmed as a device, Rule 21 can still produce Class III if anything is absorbed systemically, and a lot of substance-based products are systemically absorbed at least partially. This is one of the hardest classification exercises in the MDR, and it is also one of the most common product categories being reclassified from the old directive regime.

Rule 22. Active therapeutic devices with integrated diagnostic function

Scope. Rule 22 covers active therapeutic devices with an integrated or incorporated diagnostic function which significantly determines the patient management by the device, such as closed-loop systems or automated external defibrillators. These are Class III.

Typical devices. Automated external defibrillators (AEDs). Closed-loop insulin delivery systems (artificial pancreas systems). Closed-loop ventilators that adjust therapy based on integrated sensing. Implantable cardioverter-defibrillators fall under this logic together with the Rule 8 long-term implant provisions.

The trap. Rule 22 is the rule most likely to be missed by software-plus-hardware startups building autonomous therapeutic systems. The founders think about Rule 9 for the therapeutic action and Rule 11 for the software. Rule 22 catches the system as a whole when the diagnostic function significantly determines patient management, and the class is III regardless of what Rule 9 or Rule 11 produced individually. For any product where the device itself is making treatment decisions based on its own measurements. Without a clinician in the loop. Rule 22 needs to be the first place you look, not the last.

The Subtract to Ship angle on the special rules

The Subtract to Ship framework for MDR compliance treats classification as the second of its four passes. Inside the Classification Pass, the special rules are where subtraction gets dangerous if you do it wrong. And where it is most valuable when you do it right.

Dangerous first. Skipping the special-rules walk to save time produces a classification that looks lean but is wrong, and a wrong classification discovered at the Notified Body gate burns months and six figures of rework. This is not a pass you can subtract from. Run it every time.

Valuable when done right. The special rules also produce defensible lower classifications for founders who read them carefully. A nanomaterial device with rigorous exposure assessment can land at Class IIa under Rule 19 instead of defaulting to Class III. A substance-based product with a clearly documented non-systemic local effect can land at Class IIa under Rule 21 instead of being assumed to be Class III by default. A combined therapeutic-diagnostic product that does not actually meet the "significantly determines patient management" threshold of Rule 22 can be argued out of Class III if the documentation supports it. The key in every case is specificity: the rule, the paragraph, the intended purpose under Article 2(12), and the supporting evidence. Vague arguments lose. Specific arguments backed by documentation win.

This is the same discipline the book applies to every other regulatory decision. Subtraction is not the same as shortcut. The goal is to find the lowest defensible class, not the lowest imaginable one.

Reality Check. How well do you know the special rules that apply to your device?

  1. For your device, have you walked through each of Rules 14 to 22 and noted whether it could apply, or did you stop at the first rule that fit in the non-invasive, invasive, or active family?
  2. If Rule 14 might apply, have you documented the mode-of-action analysis distinguishing device action from medicinal-product action for any substance in the product?
  3. If Rule 18 might apply, have you traced every material of biological origin in the device and confirmed the human-vs-animal branch, and the "intact skin only" exception if relevant?
  4. If Rule 19 might apply, have you assessed the potential for internal exposure to nanomaterial on a risk basis, with evidence, rather than assuming a tier?
  5. If Rule 21 might apply, have you documented the physical mode of action and the degree of systemic absorption or local dispersion?
  6. If Rule 22 might apply, have you tested whether the diagnostic function "significantly determines" patient management, or whether a clinician remains in the loop?
  7. For whichever special rules apply, have you cited the specific rule number, the specific sub-rule, and the intended purpose under Article 2(12)?
  8. Have you cross-checked the result against MDCG 2021-24 (October 2021) and searched the Borderline Manual v4 (September 2025) for comparable precedent?

Frequently Asked Questions

Do Rules 14 to 22 replace the earlier classification rules, or do they apply in addition? They apply in addition. Annex VIII Section 2 contains the implementing rules, and one of them is unambiguous: when several rules apply to the same device based on its intended purpose, the strictest rule and sub-rule resulting in the higher classification applies. That means a device caught by Rule 9 at Class IIa and by Rule 22 at Class III is a Class III device. The special rules never reduce a class; they can only match it or raise it.

Which special rule most often catches startups off-guard? Rule 19 on nanomaterial, Rule 21 on substance-based devices, and Rule 22 on closed-loop therapeutic systems are the three that show up unexpectedly in startup conversations most often. Rule 19 because advanced materials are everywhere and founders do not always check whether they trigger a special rule. Rule 21 because substance-based devices are a growing product category and the borderline with medicinal products is subtle. Rule 22 because any autonomous therapeutic system with integrated sensing is at risk of being Class III and founders tend to underestimate that.

If Rule 14 applies, does that mean the product is a medical device rather than a medicinal product? Rule 14 only applies when the device is already confirmed as a medical device with an ancillary medicinal substance. If the substance is the principal mode of action, the product is a medicinal product regulated under the pharmaceutical framework and outside the MDR entirely. Determining which framework applies is a borderline question that has to be answered before classification, not as part of classification. MDCG 2021-24 and the Borderline Manual v4 address both questions, and early Notified Body or competent authority dialogue is often the safest path when the answer is not obvious.

How does the "intact skin only" exception in Rule 18 work in practice? It is narrow. The exception applies when the device uses non-viable tissues or cells of animal origin (not human origin) and is intended to contact intact skin only. Any contact with injured skin, mucous membrane, or any deeper tissue removes the exception and returns the device to Class III. A wound dressing using animal-origin collagen does not qualify because wounds are, by definition, not intact skin. A topical cosmetic-adjacent product using animal collagen might qualify if the intended purpose and the use conditions genuinely restrict it to intact skin. And even then the borderline with cosmetics needs to be checked.

How do I defend a lower class under Rule 19 for a nanomaterial device? With evidence. The class under Rule 19 depends on the potential for internal exposure: negligible (IIa), low (IIb), medium or high (III). Defending a lower tier requires documented analysis of the nanomaterial's location in the device, the conditions under which it could be released, the likelihood of internal contact, and the exposure quantification if release is possible. The Notified Body will review this during conformity assessment and can challenge the tier. The right approach is a risk-based internal exposure assessment completed and documented before filing, not an assertion defended after the fact.

Is Rule 22 about AI-based medical devices? Rule 22 is about closed-loop therapeutic systems generally, whether they use AI or not. An automated external defibrillator is an AED under Rule 22 whether or not AI is involved. What matters is that the device has a diagnostic function that significantly determines patient management and that the therapeutic action happens automatically. AI-based closed-loop systems are caught by Rule 22 for the same reason, but so are non-AI closed-loop systems. The rule does not single out artificial intelligence, and no separate "AI rule" exists in the current MDR text.

Sources

  1. Regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices, Article 2(12) (intended purpose), Article 51 (classification), and Annex VIII Section 2 (implementing rules) and Section 3 Rules 14 to 22. Official Journal L 117, 5.5.2017.
  2. MDCG 2021-24. Guidance on classification of medical devices, October 2021.
  3. Manual on borderline and classification for medical devices under Regulation (EU) 2017/745 and Regulation (EU) 2017/746, Version 4, September 2025 (Borderline and Classification Working Group of the MDCG).

This post is part of the Device Classification & Conformity Assessment series in the Subtract to Ship: MDR blog. Authored by Felix Lenhard and Tibor Zechmeister. The special rules summarised above are the orientation layer. Every specific classification must be made against the full text of Annex VIII, cross-checked with MDCG 2021-24 and the Borderline Manual v4, and documented with a specific rule citation and an intended-purpose reference under Article 2(12). When a device sits close to the border between Rule 14, Rule 18, or Rule 21 and the medicinal-products or tissues-and-cells frameworks, the fastest way to a defensible answer is usually a working session with a sparring partner who has navigated that border before.