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This guide is general information about US labeling rules, not medical advice and not guidance for any individual patient. It is for lab, clinic and supply staff who see “Rx only” on a package and need to know what it signals and which rule sits behind it.
Short answer
“Rx only” (also written “℞ only”) is the symbol statement US law uses to show that a product is restricted to prescription or practitioner-order distribution. For drugs, federal law requires the label to bear at least “Rx only” before dispensing. For devices, 21 CFR 801.109 accepts either the symbol statement or a longer “Caution: Federal law restricts this device to sale by or on the order of a ___” line.
Definition and scope
The symbol is a labeling statement, not a quality grade or a certification. Two separate US rules produce it, and they are worded differently:
- Drugs. Section 503(b)(4) of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 353(b)(4)) says a drug subject to the prescription requirement is misbranded if, before dispensing, its label does not bear at least the symbol “Rx only”. FDA’s drug labeling rule at 21 CFR 201.100(b)(1) likewise lists the statement “Rx only” among the label requirements for prescription drugs for human use.
- Devices. 21 CFR 801.109 covers prescription devices: those that, because of potential for harmful effect, method of use or collateral measures needed, are not safe except under the supervision of a licensed practitioner. This guide covers the US rules only; other jurisdictions use their own wording and symbols.
How the statement is used on labels
Under 21 CFR 801.109(b), the label of a prescription device, other than surgical instruments, must bear two things: the symbol statement “Rx only” or “℞ only” (or the full caution statement), and the method of the device’s application or use. The blank in the caution statement is filled with “physician”, “dentist”, “veterinarian”, or a designation for another practitioner licensed by the state where that practitioner practices.
The same section sets the distribution side. The device is held by a person lawfully engaged in manufacture, transport, storage or distribution, or by a licensed practitioner, and is to be sold only to or on the prescription or other order of such a practitioner for use in the course of professional practice. Labeling for the practitioner must carry information for use, including indications, effects, methods and relevant hazards, though that information may be omitted from the dispensing package when it is commonly known to practitioners.
Manufacturer labels show both forms in practice. Pages such as StatLock catheter securement and the Buretrol burette IV set list products labeled “Rx only”, while the port needle guide quotes a manufacturer’s caution statement that US federal law restricts sale of the device to or on the order of a physician. Both forms are the two options 801.109(b)(1) names.
Label checklist: drug versus device
| Product on the label | What the regulation says | Source |
|---|---|---|
| Prescription drug | Label must bear at least the symbol “Rx only” before dispensing; absence means misbranded. | 21 U.S.C. 353(b)(4)(A); 21 CFR 201.100(b)(1) |
| Drug not subject to the prescription requirement | Label bearing “Rx only” makes the drug misbranded. | 21 U.S.C. 353(b)(4)(B) |
| Prescription device (not a surgical instrument) | Label bears “Rx only”, “℞ only” or the full caution statement, plus the method of application or use. | 21 CFR 801.109(b) |
| Prescription device that is a surgical instrument | The 801.109(b) label requirement is written to exclude surgical instruments. | 21 CFR 801.109(b) |
The checklist for a package in hand: (1) Is it a drug or a device? (2) Which form appears: “Rx only”, “℞ only”, or the full caution line? (3) If the caution line appears, which practitioner is named in the blank? (4) For a device, is the method of application or use stated? (5) Is the item a surgical instrument, in which case the absence of the symbol is not itself a labeling gap under 801.109(b)?
Where it matters for labs, clinics and supply decisions
For receiving and storage staff, the statement identifies which items are in the prescription category, so that they are held and sold only on the order described in the regulation. The reverse rule matters just as much: because a non-prescription drug bearing the symbol is misbranded, the statement is evidence of a product’s prescription status as the manufacturer has labeled it. For a fuller map of drug labeling sections, see FDA prescription drug labeling: the 201.56/201.57 section map.
Common misunderstandings
It is not a quality or safety mark
The statement records a distribution restriction. Neither 503(b)(4) nor 801.109 treats it as an endorsement or a performance rating.
It is not a dosing instruction
The symbol says nothing about how much of anything to use. Use information for a drug or device comes from its own labeling.
It does not mean the item was prescribed to the person holding it
The symbol sits on the manufacturer’s label before dispensing. Prescribing is a separate act by a licensed practitioner.
“℞ only” and “Rx only” are not different rules
801.109(b)(1) lists both as acceptable forms of the same symbol statement.
FAQ
What does “Rx only” mean on a label?
It is the US symbol statement showing that a drug or device is restricted to prescription or practitioner-order distribution. The legal source is 21 U.S.C. 353(b)(4) for drugs and 21 CFR 801.109 for devices.
Can an over-the-counter drug carry “Rx only”?
No. Under 21 U.S.C. 353(b)(4)(B), a drug that is not subject to the prescription requirement is deemed misbranded if its label bears the symbol.
Is the full caution statement an alternative for devices?
Yes. 21 CFR 801.109(b)(1) accepts “Caution: Federal law restricts this device to sale by or on the order of a ___” in place of the symbol statement.
Do surgical instruments need the statement?
The label requirement in 801.109(b) applies to the label of a device “other than surgical instruments”.
Sources
Checked 2026-10-30.
- 21 CFR 801.109, Prescription devices: https://www.law.cornell.edu/cfr/text/21/801.109
- 21 U.S.C. 353(b)(4), Federal Food, Drug, and Cosmetic Act section 503(b)(4): https://www.law.cornell.edu/uscode/text/21/353
- 21 CFR 201.100, Prescription drugs for human use: https://www.law.cornell.edu/cfr/text/21/201.100
