One Medication, More Than One Purpose
Understanding Multiple and Off-Label Uses
Have you ever looked at a medication and wondered, “Why is this person taking a seizure medication for bipolar disorder?” I have even overheard medical professionals make comments such as, “Why are they taking this for depression? That medication is for seizures.” Statements like this demonstrate exactly why continuing education and staying current with medical information are so important.
A medication's original purpose is not necessarily its only purpose. Many medications influence receptors, neurotransmitters, hormones or other biological pathways involved in more than one condition. As researchers gather evidence and clinicians observe patient outcomes, a medication initially developed for one problem may become an established treatment for something entirely different.
This has happened throughout medicine, and psychiatry is no exception.
How does a medication acquire another use?
A medication may have more than one purpose for several reasons:
Its mechanism affects more than one organ system or disease process.
A beneficial effect is noticed during clinical use or research.
Later studies confirm that it is effective for another condition.
The FDA subsequently approves the additional indication.
Clinicians may prescribe it off-label when credible evidence and sound clinical judgment support doing so.
The FDA explains that an off-label use can involve prescribing an approved medication for a different condition, dose, age group or route than the approved labeling specifies. Healthcare professionals generally may do this when they determine that it is medically appropriate for an individual patient. However, the FDA has not evaluated and approved that particular use in the same way it has an on-label indication. Learn more from the FDA.
Familiar examples from general medicine
These medications show how dramatically a drug's use can expand:
Minoxidil was used orally for severe hypertension. Its hair-growth effect eventually led to topical and oral use for hair loss, although oral minoxidil for hair loss remains off-label.
Sildenafil was investigated for cardiovascular conditions before becoming best known for erectile dysfunction; it is also approved in specific formulations for pulmonary arterial hypertension.
Finasteride was first approved for benign prostatic hyperplasia and later approved at a different dose for male-pattern hair loss.
Metformin is a foundational treatment for type 2 diabetes but is also frequently prescribed off-label for polycystic ovary syndrome and antipsychotic-associated weight gain.
Botulinum toxin was initially used for eye-muscle disorders and is now used for conditions including chronic migraine, spasticity, excessive sweating and cosmetic wrinkles.
Hydroxychloroquine originated as an antimalarial medication and is now routinely used for autoimmune disorders such as lupus and rheumatoid arthritis.
Psychiatry offers many important examples
Some medications used in mental healthcare began in entirely different areas of medicine. In certain cases, clinicians noticed improvements in mood, behavior, anxiety or other symptoms, and research later clarified where the medication was, and was not beneficial.
Anticonvulsants that became mood stabilizers
Calling a medication a “seizure drug” does not mean it only treats seizures. Several anticonvulsants influence neuronal signaling to stabilize mood primarily by reducing hyperexcitability, altering ion channel activity, and shifting neurotransmitter balance:
Valproate/divalproex is used for epilepsy and is also FDA-approved for manic episodes associated with bipolar disorder. It is also used for migraine prevention. Because valproate carries major pregnancy-related risks, its selection requires especially careful assessment and counseling.
Carbamazepine treats certain seizure disorders and trigeminal neuralgia, and an extended-release product is approved for acute manic and mixed episodes associated with bipolar I disorder.
Lamotrigine began as an antiseizure medication and is also approved for maintenance treatment of bipolar I disorder. It is not an acute antimanic treatment, and slow titration is essential because of the risk of serious rash.
Topiramate treats epilepsy and is also approved for migraine prevention. It is sometimes used in psychiatric practice for other purposes, but those uses must be evaluated individually because evidence varies. FDA labeling confirms its established epilepsy and migraine indications. FDA prescribing information for Topamax.
Cardiovascular medications used in mental healthcare
Clonidine was developed as an antihypertensive medication. Extended-release clonidine is also FDA-approved for ADHD in children and adolescents, either alone or with a stimulant.
Guanfacine is another blood pressure medication whose extended-release formulation is approved for ADHD.
Propranolol is used for cardiovascular conditions, migraine prevention and essential tremor. It is also prescribed off-label for the physical symptoms of performance anxiety, such as a racing heart and trembling.
Prazosin is an alpha-1 blocker developed for hypertension. It is sometimes prescribed off-label for trauma-related nightmares, although evidence is mixed and treatment should be individualized.
Other medications that crossed into psychiatry
Hydroxyzine is an antihistamine that also has an FDA-approved indication for the symptomatic relief of anxiety and tension.
Bupropion is an antidepressant whose active ingredient is also approved under another brand for smoking cessation.
Gabapentin was developed for seizure management and is approved for postherpetic neuralgia. It is sometimes used off-label in psychiatric and substance-use settings, but the strength of evidence depends on the specific condition.
Dextromethorphan has long been used as a cough suppressant. In combination products and specific formulations, it is now used for pseudobulbar affect and major depressive disorder.
These examples do not mean that every medication works for every person or that every possible use is supported by good evidence. They demonstrate that a drug class describes part of a medication's history or mechanism, not the full range of its potential clinical applications.
FDA-approved and off-label are not the same thing
An FDA-approved indication has been formally reviewed for a particular condition, population, formulation and dosing plan. An off-label use means an approved medication is being used in a way that is not included in its current FDA labeling.
Off-label does not automatically mean unsafe, improper or experimental. Some off-label practices are supported by clinical guidelines and substantial research. Others have limited or conflicting evidence. That distinction matters. The appropriate questions are not merely, “What drug class is this?” or “What was it originally made for?” Better questions include:
What symptom or diagnosis is being targeted?
What evidence supports this particular use?
Are approved alternatives available or appropriate?
What are the expected benefits and significant risks?
How will effectiveness, adverse effects and interactions be monitored?
Does the patient understand the treatment plan and alternatives?
The bottom line
Medicine is rarely as simple as “this pill treats only one thing.” A medication may have several FDA-approved indications, accepted off-label uses or emerging uses still being studied. This is particularly relevant in psychiatry, where medications originally used for seizures, high blood pressure, or other medical conditions may relieve carefully selected mental health symptoms.
Patients should never start, stop or change a medication based solely on something they read online—or because someone unfamiliar with their treatment questions why it was prescribed. Medication decisions should be based on the individual's diagnosis, symptoms, medical history, concurrent medications, current evidence and an informed discussion with the prescribing professional.
Staying educated matters. Staying current matters. Most importantly, understanding the reason a medication was selected matters far more than assuming it has only one purpose.
Educational disclaimer: This article is for general educational purposes and does not replace individualized medical advice, diagnosis or treatment. Never start, stop or change a prescription without consulting a qualified healthcare professional.
SHINE Insights | SHINE Primary & Psych Care
