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Drug Names and Their Pharmaceutical Salts - Clearing Up the Confusion

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on June 15, 2024.

Drugs are often made into their chemical salt forms to enhance how the drug dissolves, boost its absorption into your bloodstream, and increase the effectiveness. Without absorption, a drug cannot have a therapeutic effect, so some forms require a salt. Many medications also need a salt attached to be water-soluble.

Maybe you've had questions about drugs names and differences. For example, you're prescription for your new diabetes medication calls for metformin hydrochloride, but when you receive your bottle and look it up on the Internet, all you see is “metformin”, not “metformin hydrochloride.” Why is this? Is it the same drug your doctor ordered? And what is “hydrochloride”?

Why do some drugs exist in salt forms?

Over 50% of all drug molecules used in medicine exist as salts, most frequently as the hydrochloride, sodium, or sulfate salts. Drugs are often formed as a weak acid or base, but these forms are not always optimal for dissolution or absorption into your body. Adding an inactive salt to a drug can help increase its absorption and effectiveness.

The choice of a salt in the lab is determined primarily by how acidic or basic the chemical is (the pH), the safety of the ionized form, the intended use of the drug, how the drug is given (for example, by mouth, injection, or on the skin), and the type of dosage form (such as tablet, capsule, or liquid).

Drug salt formation allows also for development of controlled-release dosage forms, improved stability to extend shelf life, targeted drug delivery in the gastrointestinal tract (stomach or intestine), improved taste, reduced injection pain, ease of processing, and an extended patent life.

Top 15 Most Common Drug Salts

Note: as a percentage of salt form as a function of all medicinal compounds

Can I switch around between different drug salts?

Most drug salts should not be switched unless okayed from your doctor or pharmacist. If you plan on using a drug that exists in a different salt form from the one your doctor originally prescribed, be sure to get your healthcare provider’s approval. There may be important differences in drug absorption, dosing, or uses.

According to FDA, drug products are considered pharmaceutical alternatives (not pharmaceutical equivalents) if they contain the same therapeutic moiety (active ingredient), but are different salts. An example of this would be tetracycline hydrochloride 250 mg capsules and tetracycline phosphate complex 250 mg capsules. 

Most drug salts do not lend a therapeutic action to a drug, other than enhancing how well it dissolves, how it is absorbed, or its formulation characteristics. There are a few drug salts may have an added therapeutic effect. The United States Pharmacopeia (USP) Salt Policy states if the active ingredient in a drug product is a salt form, the drug product monograph will only be called by its active ingredient drug name, without the salt at the end of the name. An example of this naming convention is metformin hydrochloride, a salt form where the active ingredient is metformin, the salt (with no therapeutic action) is hydrochloride, therefore this medicine is referred to as "metformin".

Why are drugs called by both their “parent drug name” and “salt” name?

An example is the best way to explain this question. The nonprescription (over-the-counter or OTC) version of prescription omeprazole (Prilosec) is omeprazole magnesium (Prilosec OTC). Prilosec OTC is the magnesium salt of omeprazole in a delayed-release capsule form.

Whether omeprazole has a salt or not really results in little difference is how well it works, although, according the FDA, they are not bioequivalent or interchangeable. In fact, they have different uses based on the clinical studies completed. Prescription Prilosec is indicated for multiple acid-related conditions, like ulcer treatment or erosive esophagitis, while Prilosec OTC is only indicated for “heartburn” (gastroesophageal reflux disease or GERD) in adults.

Erosive esophagitis is a condition that should not be treated without first consulting a doctor. Heartburn can be treated short-term with OTC medications. But your doctor may suggest you use Prilosec OTC for other “off-label” conditions (like erosive esophagitis), especially if your insurance does not cover the prescription drug due to the availability of the OTC product.

Is “tramadol” the same drug as “tramadol hydrochloride”?

Often, generic drug names will be used by healthcare providers and the general public without the salt ending, just out of convenience. For example, while the narcotic-like painkiller tramadol and tramadol hydrochloride (HCL) may sound like two different drugs, they are actually the same drug.

The official name is tramadol hydrochloride, but commonly it is often just shortened to “tramadol”. That may be how your doctor writes it on the prescription and how it reads on your pharmacy label. However, oral tramadol only exists in its salt form “tramadol hydrochloride”, even though people don’t always refer to that name.

Brands names for tramadol include Qdolo and ConZip. 

When you check for a drug interaction, you may run into the same problem. While the official name of the drug may include a salt name, the text written for the drug interaction may not include the salt name because the drug is more commonly referred to without it’s salt name, as is the case with oral tramadol.

Check for drug interactions at the Drugs.com Interaction Checker.

Remember that only about 50% of drugs are linked with salts; the others are called by the “parent” name because they exist as a free acid or base and do not require a salt formulation to be active in the body.

If you are unsure about the true name of your drug, be sure to check with your pharmacist or look at the manufacturer’s package insert provided with your prescription.

Does a salt form add any therapeutic effect to the drug?

It depends. Usually, the salt form of a drug does not lend therapeutic qualities to the active ingredient. It’s primary purpose is to enhance pharmaceutical characteristics like dissolution, absorption, and onset of action. Different salt forms may not be bioequivalent, meaning that the therapeutic effect in the body is not expected to be the same.

On the other hand, some drugs may have qualities where the salt does lend a therapeutic effect, and for this reason it is important to check with your pharmacist and physician to make sure that different salt forms can be interchanged. Your pharmacist can check The Orange Book, which will define if the drugs are “AB” rated, meaning they are bioequivalent.

Drug names can be confusing for healthcare providers and patients alike. If you have questions about a particular drug or its salt form, be sure to ask your pharmacist, who can provide detailed information to both you and your doctor, if needed.

Can a drug salt be patented?

Yes, drug salts can be patented when combined as part of a proprietary drug product by a pharmaceutical manufacturer. A new salt form may alter how a drug can be given or it’s dosage form.

New patent timelines are normally issued with the new molecular entity. Omeprazole was originally developed in a capsule dosage form, but was later formulated into a tablet after it was combined with a magnesium salt.

The unauthorized use of a proprietary salt form is restricted by patent law, and often results in legal battles between drug manufacturers. It's also a common way a drug company may try to extend the patent life on an active ingredient in a medication.

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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