PRN: As Required Medication

PRN is a medical abbreviation that means “as needed” and originates from the Latin phrase “pro re nata”. It is used for medication that is needed when symptoms arise, rather than at fixed scheduled times.

The abbreviation PRN can also show up for other terms such as packaging recovery notes in UK recycling systems and in United States job adverts for as needed nursing shifts, but here we will cover the PRN prescription meaning.

At a glance: PRN

What does PRN mean on a prescription?

When PRN is seen on a prescription, such as an FP10 form, it means they are not needed on a regular schedule. 

In the UK, the NHS app, which stores your medical records may use the term PRN for medication that has been prescribed on an as-needed basis.

On prescription labels, the term PRN may be used as well as the full written form “as needed” or “as required” to ensure patients don’t get confused. 

Instructions for a PRN medication may be written as “1 to 2 tablets every four hours as needed for pain, maximum of four doses (eight tablets) in 24 hours.”

With any PRN medication, prescribers will always include a maximum dose that can be taken in a 24-hour timeframe.

A maximum dose is given to prevent adverse side effects from high doses of medication, every drug has a point where instead of being effective, it becomes toxic so it is important not to exceed the maximum dose on your prescription label.

Common PRN medications

There are many medications that use a PRN dosing schedule, some of the most common are:

• Paracetamol

• Ibuprofen

• Antihistamines

• Reliever Inhalers

• Laxatives

• Antacids 

• Anti-sickness

PRN dosing and medical cannabis

Medical cannabis is a prescription-only medication that has been legal in the UK since November 2018.

It must be prescribed by specialist doctors on the General Medical Council's Specialist Register (GMC). 

Medical cannabis may be prescribed with a PRN dosing schedule, our specialist team at Releaf will assess whether this type of schedule could be the right fit for you.

A PRN medical cannabis prescription might benefit those with chronic pain conditions who experience symptom flare-ups, it could also work for patients with intermittent episodes of anxiety.

Some medical cannabis prescriptions may use a mix of dosing schedules, for example, a scheduled background dose with a PRN allowance for breakthrough symptoms. 

For those who may use a PRN dosage of medical cannabis, a vaporiser might be a suggested format as it has a fast onset of effects.

A PRN medical cannabis prescription may read "Inhale 0.1g–0.2g PRN, maximum 3 times daily." That means the patient should take the dose when they experience symptoms up to a maximum of three doses a day.

Like with all medications, it is important to stay within prescribed limits of medical cannabis and track symptoms between appointments so that you can get the right care.

PRN vs scheduled dosing

PRN differs from scheduled dosing such as BD (twice daily) and TDS (three times daily). 

Scheduled dosing like the two mentioned above are taken at regular intervals regardless of symptoms while PRN gives patients discretion on when to dose.

A scheduled dosing system is more often used to keep drug levels steady in the blood, antibiotics will use a scheduled dosing system to ensure the drug stays steady and fight the infection.

Whereas a PRN dosage is used for symptoms that are intermittent or less predictable, for example, asthma patients may need a reliever inhaler when running, but not every day.

PRN also differs from STAT medication which means “at once.” 

STAT refers to a medication that needs a single dose given immediately for an urgent situation, like an EpiPen for allergic reactions. Whereas PRN is to be taken as needed when symptoms occur, such as paracetamol for a headache.

PRN and other dosing abbreviations 

Is PRN dosing right for you?

A PRN medical cannabis dosing system will be determined by our specialist team at Releaf. 

It is always important to discuss medication dosing with your prescriber and to never exceed the maximum 24-hour dosing limit.

A medical cannabis prescription does not automatically give you the right to drive and you must not be impaired while driving.

Frequently asked questions about PRN prescriptions

What does PRN stand for?

PRN is an abbreviation that comes from the Latin phrase “pro re nata” and means “as needed.”

What does PRN mean in medical terms or on a prescription?

When PRN is found on a prescription or medical records it means the medication prescribed should be taken as needed and does not need a fixed schedule.

What does PRN mean in the NHS?

The term PRN is used in the NHS to describe medicines that are to be taken as needed.

What are PRN medications used for, and why do doctors prescribe them?

PRN medications are used to alleviate symptoms that are intermittent. Doctors may prescribe antihistamines for those with summer allergies to be taken on high-pollen count days or paracetamol for occasional headaches.

What are common PRN medications? Is paracetamol a PRN medication?

There are lots of medications that are commonly prescribed with a PRN dosage, pain killers like paracetamol and ibuprofen are considered PRN medications. Antacids for heartburn, antihistamine for allergies and reliever inhalers for asthma are also PRN medications.

When should you take PRN medication?

A PRN medication is designed to be taken when symptoms occur and do not need a fixed schedule of dosing. PRN medications come with a maximum limit of medication you can take in a 24-hour time frame.

What is another term for PRN?

PRN medications are also known as “as needed” and “as required” medications and prescription leaflets may use this instead of the PRN abbreviation.

How is PRN different from scheduled or STAT doses?

PRN is different from scheduled and STAT prescriptions as it is only to be taken when required. Scheduled prescriptions have a fixed timing and STAT medications are for immediate use in urgent situations.

To find out if you are eligible, try our free medical cannabis eligibility checker, it takes less than 30 seconds to fill in.

Our medical cannabis glossary can also help you learn more about terms you may associate with medical cannabis. 

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