What Drug Names Really Mean

Full update September 2017

In recent years, there have been numerous examples of new formulations of old drugs coming to market. For example, we have seen new formulations of naloxone as Narcan Nasal Spray and Evzio (U.S.), topiramate (Qudexy XR [U.S.]), and doxepin (Silenor). Sometimes these formulations offer advantages, such as more convenient dosing or fewer side effects. Other times, the benefits are less clear or there’s really no difference at all. Unfortunately, the availability of new formulations can increase the risk of medication errors due to confusion associated with drug names, suffixes, etc. Also, new formulations tend to be more expensive than their older counterparts. Understand the ins and outs of different formulations of drugs and nuances associated with drug names to help your patients get the most appropriate therapy.

Toujeo Solostar, inject 30 units every night at bedtime, #1 package, 3 refills

Mrs. Johnson, a 52-year-old patient, brings in a new prescription for Toujeo SoloStar (insulin glargine, 300 units/mL), inject 30 units every night at bedtime. This is her first prescription for any kind of insulin product. She tells you that her husband also uses insulin but he uses Lantus (insulin glargine, 100 units/mL). Since they are on the same insurance plan, she wants to make sure that her insulin product will be the same co-pay as her husband’s, which is $30.

Why are some Rx drugs available in multiple or new formulations?

Multiple or new formulations of a drug may be available for a few different reasons. The new formulation of a drug may make a drug more effective, safer, or convenient over the original formulation. A drug company may be able to extend their patent on a brand-name product by developing a new formulation. Or another company might be able to make a different formulation of a drug due to a patent loophole. (An example of this is esomeprazole strontium [U.S.].)

Patent extension. Just as with other inventions or products, brand-name drugs are protected by patents. When a patent expires, less expensive generic versions of the drug can come to the market. One way that a drug manufacturer can qualify for a patent extension is to develop a newer formulation of a brand-name drug. In these cases, the newer formulation is different enough to get a new patent. By doing this, the company can add on more years to sell their drug even if a generic comes to market to compete. Generics for the older formulations might be available, but the newer formulations are often heavily marketed to sway prescribers.

For example, Ambien CR (zolpidem controlled-release [U.S.]) was marketed within the year before Ambien (zolpidem [U.S.]) went generic. Same for Paxil CR (paroxetine controlled-release). In the U.S., new formulations of Sular (nisoldipine) and Tricor (fenofibrate) also benefitted drug companies with regard to patent life.

Another way to extend the patent is to find new indications for use. For example, Intuniv (U.S.) and Intuniv XR (Canada) contains the old drug guanfacine. Guanfacine (Tenex [U.S.], etc) was originally approved by the Food and Drug Administration (FDA) in 1986 for the treatment of high blood pressure. Intuniv was approved many years later in 2009 for the treatment of attention deficit hyperactivity disorder (ADHD).

Therapeutic benefit. Occasionally, a new formulation of an old drug has the potential to offer benefits over the old formulation. One example of this is Requip XL (ropinirole extended-release [U.S.]). There’s information to suggest that Requip XL might be better than regular Requip at controlling some of the symptoms of Parkinson’s disease. Another example is metformin extended-release (Glumetza, etc) which is associated with less gastrointestinal side effects than immediate-release metformin (Glucophage, etc).

But sometimes there aren’t any significant therapeutic benefits. For example, Paxil CR was supposed to cause less nausea over the first week of therapy than regular Paxil. However, about the same number of patients stopped taking these formulations because of nausea.

Dosing convenience. Many times, new formulations offer less frequent dosing, which can improve patient compliance. There’s a long list of examples. Invokamet XR (canagliflozin and metformin extended-release [U.S.]) is given once daily and regular Invokamet is given twice a day. Requip XL is given once daily and regular Requip is given three times a day. The dosing schedule for Wellbutrin XL (bupropion extended-release) is once daily. Wellbutrin SR (bupropion sustained-release) is given twice a day. Regular Wellbutrin (bupropion [U.S.]) is given three times a day. Rituxan Hycela (rituximab [U.S.]) and Rituxan SC (Canada) can be given subcutaneously while regular Rituxan is an IV infusion. The subcutaneous dosage form allows for the convenience of a shorter administration time. Rituxan Hycela and Rituxan SC can be administered over just a few minutes, versus several hours for a Rituxan IV infusion.

What do common drug name suffixes (CR, ER, XL, etc) mean?

Many new formulations will have suffixes on the ends of their names. These suffixes may represent different release mechanisms for a drug. For example, LA stands for “long-acting,” ER or XL for “extended-release,” etc. These suffixes may give you a clue about dosing frequency, but you should never assume. For example, “CR” usually stands for “controlled-release,” but it doesn’t always mean that the formulation is dosed just once daily. Coreg CR (carvedilol extended-release [U.S.]) is given once daily, but Zyflo CR (zileuton controlled-release [U.S.]) and Tegretol CR (carbamazepine extended-release [Canada]) are given twice a day. “Controlled-release” may even refer to where the drug is released in the gastrointestinal tract, instead of referring to its onset of action, such as with Paxil CR. Both Paxil and Paxil CR are given once a day. But the controlled-release formulation allows Paxil CR to be released in a different part of the gastrointestinal tract than with the immediate-release formulation.

Sometimes, there are formulations with different suffixes that are available in the same strengths. Some examples include Wellbutrin SR and Wellbutrin XL 150 mg tabs and Depakote (divalproex delayed-release [U.S.]) and Depakote ER (divalproex extended-release [U.S.]) in 250 mg and 500 mg strengths. Ritalin LA (methylphenidate long-acting [U.S.]) and Ritalin-SR (methylphenidate sustained-release) are both available in a 20 mg strength. Double check that you are selecting the drug with the right suffix.

Keep in mind that suffixes aren’t always about different release mechanisms or salts. Sometimes they can help guide you to other specifics. For example, the suffix in Terazol 3 (terconazole) means the product is for three days of therapy, NovoSeven RT (coagulation factor VIIa [U.S.]) means the product can be stored at room temperature, Betapace AF (sotalol [U.S.]) means it is approved for the treatment of atrial fibrillation, and Nipride RTU (nitroprusside [U.S.]) is meant to distinguish that this dosage form is ready to use.

What should I know about drugs that are available as different salt forms?

There are a number of drugs that are available as different salt forms. This has to do with the chemistry of the drug and pairing up the drug molecule with another “piece,” such as hydrochloride, phosphate, sulfate, etc. A classic example is hydroxyzine. It comes as hydroxyzine hydrochloride (Atarax) and hydroxyzine pamoate (Vistaril [U.S.]). There isn’t a significant difference between the two, although similar to other drugs in different salt forms, they can’t generally be automatically substituted for one another.

An example where there is a significant difference is with metoprolol tartrate (Lopressor) and metoprolol succinate (Toprol-XL [U.S.]). Metoprolol succinate is a long-acting formulation, and it is preferred over metoprolol tartrate for patients who have heart failure. We have a chart, Drugs with Different Salt Forms, that covers commonly used meds that come as different salts, with descriptions of the differences between the salt forms.

Do insurances typically cover newer drug formulations?

Usually, a newer formulation of a drug is more expensive or not covered by insurance. This is especially true if there’s not a generic available for the formulation. Some third parties will cover any formulation of a drug, while others will require substitution of a generic or less expensive formulation. In many cases, the rejection message from the insurance company will specify what drug or formulation to use as an alternative. When this occurs, it’s important to alert the pharmacist since the prescriber may need to be contacted to authorize switching the patient to the alternate product. Or a patient assistance program for the drug might be available.

You process Mrs. Johnson’s prescription for Toujeo and get a message back from her insurance company saying it’s not covered and that Lantus is preferred. You know that Toujeo and Lantus both contain the same ingredient, insulin glargine, but you aren’t sure if you could automatically substitute them. You ask the pharmacist for help before proceeding.

How can I help prevent errors with drugs that have multiple formulations?

Order entry. New or multiple formulations of the same drug increases the number of products with a particular name. It’s important to be especially careful in choosing the right product.

Alert the pharmacist right away if you notice a problem when entering a prescription for a product with multiple formulations. A mismatched dosing regimen noted at order entry is often the first clue to a prescribing error. For example, a prescription for Coreg CR 6.25 mg BID should immediately raise a red flag since this is a dosing regimen used for the immediate-release form of Coreg, not the controlled-release Coreg CR.

For a drug that comes in different salt forms, it’s important to make sure the patient gets the one that’s prescribed because the absorption, stability, tolerability, etc, can be different. If you get a prescription for a drug that has different salt forms, but the salt form isn’t specified, clarify with the pharmacist. An example of this would be an Rx written for doxycycline. You need to know whether to dispense doxycycline hyclate or doxycycline monohydrate.

Product selection. It’s also important to be extra careful when choosing a product with multiple formulations from the shelf due to the potential for confusion and mix-ups. In many cases, new formulations will be stored next to older formulations on pharmacy shelves, such as Ambien and Ambien CR. Or different salt forms might also be stored alongside one another, such as betamethasone dipropionate and betamethasone valerate. It is easy to pull the wrong product by mistake. Always double check NDC (or DIN in Canada) numbers against the prescription. Use barcode scanning technology to confirm you are picking the right product off the shelf. Consider using shelf tags, dividers, or marking bottles to help avoid mix-ups among these products in your pharmacy.

Therapeutic equivalence and generic substitution. Sometimes it is unclear which formulations of products are okay to substitute for other formulations. For example, bupropion is available as Aplenzin (U.S.), Budeprion XL (U.S.), Forfivo XL (U.S.), Wellbutrin (U.S.), Wellbutrin SR, Wellbutrin XL, Zyban, and generics. Some of these products are okay to substitute for each other, while others are not. Also as mentioned, different salts of a drug cannot generally be automatically substituted for one another.

Check with your pharmacist if you are unsure about substituting with different formulations. This can help prevent errors. Consider adding computer alerts or shelf tags for products that are easy to confuse in your pharmacy.

Storage and preparation. Not all formulations of the same drug are stored or prepared the same. For example, a newer formulation of daptomycin, Cubicin RF, is stored at room temperature while regular Cubicin is stored in the fridge. Don’t get confused by the “RF” suffix, which may suggest refrigeration. Always double check storage requirements for all drugs that are unfamiliar to you when stocking inventory.

Preparation may be different when handling injectable drugs that come in different formulations. This is the case again with Cubicin and Cubicin RF. Cubicin is reconstituted with normal saline, while Cubicin RF is reconstituted with bacteriostatic or sterile water. Always double check to make sure you are using the correct diluent when reconstituting injectable meds.

The pharmacist lets you know that she will need to call the prescriber to change the medication because even though it has the same ingredient, the concentrations are different. You let Mrs. Johnson know that the medication is not covered by her insurance. She is confused because she looked up the medication on the internet and saw that it has the same ingredient as Lantus, which is what her husband is taking. She is wondering why this drug wouldn’t also be covered. You explain to Mrs. Johnson that Toujeo is a newer, more expensive drug and her insurance company prefers that she use a less expensive drug that has been around for longer, like Lantus. Mrs. Johnson then asks you if there’s much difference in how well the two drugs work, so you ask the pharmacist to speak with her.

The pharmacist lets Mrs. Johnson know that the two drugs are very similar. She tells Mrs. Johnson that while Toujeo may last a few hours longer than Lantus, it doesn’t have much benefit over Lantus for most patients.

Project Leader in preparation of this technician tutorial (330982): Flora Harp, PharmD, Assistant Editor

Cite this document as follows: Technician Tutorial, What Drug Names Really Mean. Pharmacist’s Letter/Pharmacy Technician’s Letter. September 2017.

---Please continue for a handy Cheat Sheet for sorting through drug names---

Cheat Sheet” for Sorting Through Drug Names

Why are some Rx drugs available in multiple or new formulations?

  • Patent extension
    • Brand-name drug companies can extend the number of years they can sell their drug by creating a new formulation or finding a new indication.
  • Therapeutic benefit
    • New formulations may also provide real therapeutic benefits; for example, better control of symptoms, less side effects, etc.
  • Dosing convenience
    • New formulations can make dosing more convenient; for example, once a day instead of twice a day dosing.

What is the purpose of drug name suffixes?

  • To identify different release mechanisms
    • ER (extended-release), CR (controlled-release), LA (long-acting), etc.
  • To identify different salts
    • Hydrochloride, phosphate, sulfate, etc.
  • To provide other specific information
    • Number of days of therapy, storage, indications, etc.

How can I help prevent errors with drugs that have multiple formulations and/or similar drug names?

  • Order entry
    • Pay close attention to drug names and suffixes when entering prescriptions.
    • Alert the pharmacist if you notice mismatching dosing regimens.
    • Ensure you are picking the correct salt form.
  • Product selection
    • Watch for drugs with similar names located next to each other.
    • Double check NDC numbers (DIN numbers in Canada) against the prescription.
    • Use barcode scanning technology if available.
    • Consider using shelf tags, dividers, or marking bottles to distinguish between different products.
  • Therapeutic equivalence and generic substitution
    • Do not automatically substitute different salts of a drug for one another.
    • Check with your pharmacist if you are unsure about substituting with different formulations.
    • Consider adding computer alerts or shelf tags to prevent confusion.
  • Storage and preparation
    • Always double check storage requirements and preparation instructions, especially if a drug name or formulation is new to you.

How can I help keep costs down for patients getting new formulations of drugs?

  • Get the pharmacist involved
    • A call to the prescriber can result in switching to a cheaper alternative.
  • Help the patient navigate patient assistance programs, co-pay cards, etc.

[September 2017; 330982]

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