Narcotics and other drugs are classified into five categories, or schedules, based on the potential for misuse. They range from Schedule I drugs down to Schedule V.

The federal government classifies drugs into different schedules, depending on the substance’s medical use and the potential for misuse or dependency.

Schedule I drugs have the highest potential for misuse and the potential to create severe psychological or physical dependence. Schedule V drugs have the lowest potential for misuse.

In all, there are eight factors that determine how a drug is scheduled:

  • its actual or relative potential for misuse
  • scientific evidence of its effects
  • its overall scientific understanding
  • its history or pattern of misuse
  • the scope, significance, and duration of misuse
  • its overall risk to public health
  • its capacity for psychic or physiological dependence
  • its relationship to drugs that are already controlled

Schedule I drugs don’t have an accepted medical use and a high potential for misuse. They can’t be prescribed.

Some examples include:

It’s important to understand that different drugs have different effects and different potentials for misuse, even if they’re classified in the same group. Cannabis and ecstasy, for example, are two dramatically different substances.

It’s also important to remember that federal and state governments may have differing opinions. Although medicinal cannabis is legal in 38 states — and is otherwise legal in 21 states — it’s illegal under federal law and remains a Schedule I substance.

Schedule II drugs have an accepted medical use and a high potential for dependence or misuse. Schedule II drugs can be prescribed but have severe restrictions and limitations around use.

Schedule II drugs are often prescribed to treat severe pain, anxiety, ADHD, and insomnia.

Some examples include:

Schedule II prescriptions generally expire after 6 months, but this varies by state. For example, in Massachusetts, Schedule II prescriptions are only valid for 30 days.

Schedule II drugs typically can’t be refilled without an appointment. All prescriptions must be electronically written and signed by a healthcare professional. Schedule II prescriptions can’t be called in over the phone.

Schedule III drugs have an accepted medical use and a moderate potential for dependence or misuse. They can be prescribed with some restrictions and limitations around use.

Schedule III drugs are often prescribed for pain management, appetite suppression, and anesthesia.

Some examples include:

Schedule III prescriptions written by a physician generally expire after 6 months or five refills — whichever comes first. Schedule III prescriptions can be called in by your clinician or submitted to your pharmacy in writing.

Schedule IV drugs have an accepted medical use and a low potential for dependence or misuse. They can be prescribed with some restrictions or limitations around use.

Schedule IV drugs are often prescribed to treat chronic pain and anxiety.

Some examples include:

Schedule IV prescriptions written by a physician generally expire after 6 months or five refills — whichever comes first. Schedule IV prescriptions can be called in by your clinician or submitted to your pharmacy in writing.

Schedule V drugs have an accepted medical use and a lower potential for dependence or misuse. They’re often prescribed for pain, cough, and diarrhea management.

Some examples include:

  • diphenoxylate/atropine (Lomotil, Motofen)
  • guaifenesin/codeine (Robitussin AC)
  • parepectolin (Attapulgite)
  • pregabalin (Lyrica)

Schedule V drugs aren’t subject to the same limitations as other scheduled substances, but they aren’t as accessible as standard over-the-counter medications.

Although you may not need a prescription for a Schedule V drug, you typically have to request the medication from the pharmacist directly. They’ll ask you to present a form of photo identification, verify that you’re age 18 or older, and add your information to a database.

There may be restrictions on how frequently you can purchase a Schedule V drug.

Your doctor or other healthcare professional may recommend a controlled medication to help treat an underlying health condition, like anxiety or insomnia.

While there are standard dosage recommendations for all medications, your individual tolerance level will vary. Your clinician should work with you to determine the appropriate dose for your needs and advise you on any side effects or risks associated with use.

It’s also worth considering that different regions have different laws around prescription medication and other controlled substances.

Your prescribing clinician or pharmacist filling your prescription should be able to give you more information about appropriate use, as well as legal requirements for storing and traveling with the medication.

As a general rule, try to avoid leaving home with your medication unless it’s absolutely necessary. If you do need to take your medication with you, make sure it’s in the original packaging with your name and the date the medication was dispensed.

Many different drugs and medications are classified as controlled substances, whether they’re Schedule I, Schedule V, or somewhere in between.

You might be prescribed a controlled substance at one time or another. If you have any questions, consult with your clinician.

Adam England lives in the U.K., and his work has appeared in a number of national and international publications. When he’s not working, he’s probably listening to live music.