What Does 'As Needed' Mean On A Prescription?

You may see the Latin phrase “pro re nata” written on a prescription as the acronym PRN. In English, this phrase means “as needed.” Some medications may be prescribed to be taken as needed. They’re commonly used to treat symptoms that come up every now and then — such as pain or heartburn.

As needed medications don’t have a regular dosing schedule, rather they can be taken when you need them.

Your doctor may have limitations or recommendations for how often you can take the medication or the number of doses you can take in a day. For example, your doctor may prescribe a pain reliever to be taken every 4 to 6 hours as needed. You don’t have to take a dose every 4 to 6 hours if you don’t need it. But, if you do need to take a dose then you want to be sure not to take another dose, if you need it, until 4 to 6 after that initial dose.

Some examples of medications that may be used as needed include:

• pain and fever reducers, such as ibuprofen (Advil, Motrin) and acetaminophen (Tylenol)
• opioid medications, such as oxycodone (OxyContin) and hydrocodone/acetaminophen (Vicodin, Percocet)
• allergy medications, such as diphenhydramine (Benadryl) and cetirizine (Zyrtec)
• heartburn medications, such as calcium carbonate (Tums) and famotidine (Pepcid AC, Zantac 360)
• benzodiazepine medications, such as alprazolam (Xanax) and clonazepam (Klonopin)
• rescue inhalers, such as albuterol (Ventolin HFA, ProAir HFA, Proventil HFA)
• medications used for chest pain, such as nitroglycerin (Nitrostat)
• certain triptan migraine medications, such as sumatriptan (Imitrex) and rizatriptan (Maxalt, Maxalt-MLT)

This is not a full list of medications that may be used as needed. Also, there may be situations where your doctor recommends taking certain as needed medications every day, depending on what condition is being treated. Be sure to always follow the instructions your doctor provides for all of your medications.