5 Medications Prescribed for Off-label Use

What It Is: An injectable drug that blocks overactive nerve impulses to reduce muscle activity.

What It's Approved to Treat: Excessive underarm sweating, overactive bladder, crossed eyes, muscle spasms, chronic migraines

Common Off-label Uses: Severely cold hands, premature ejaculation, depression

Botox may be best known for smoothing and preventing wrinkles, but the manufacturer, Allergan, holds almost 800 additional patents for the drug's potential uses, including those mentioned above [source: Sifferlin]. The neurotoxin is derived from a bacterium known as Clostridium botulinum, which can cause paralysis — and even death — if it's consumed in contaminated food. But when it's administered in small doses, it can cause muscles to relax. That mechanism of action is what makes it an effective wrinkle preventer, an overactive bladder treatment (it prevents involuntary contractions that can cause the feeling of urgency).

As far as depression, a 2014 study published in the Journal of Psychiatry revealed that because facial expressions are part of the brain circuitry related to mood, inhibiting muscles in the face may prevent people from making expressions associated with negative emotions.

No matter how it's used, however, Botox does come with a long list of possible side effects including muscle weakness, drooping eyelids and double vision if the drug spreads from the injection site to other parts of the body [source: Sifferlin].

What It Is: A second-generation antipsychotic

What It's Approved to Treat: Schizophrenia, bipolar disorder and major depressive disorder (adjunct)

Common Off-label Uses: Dementia, depression, generalized anxiety disorder, OCD

Antipsychotics are increasingly being used for off-label purposes, and quetiapine (Seroquel) is the most common among them. The drug was originally registered in 1997 and was the fifth highest-selling pharmaceutical in the U.S. by 2010. But that same year, the government alleged non-psychiatrists were using the drug for off-label uses like anger management, sleeplessness and depression [source: Brett]. A 2007 study found that clinicians reported using the drug off label because it has low abuse potential, has a mildly sedative effect with low risk of confusion, and modest cardiovascular effects.

However, like other drugs in its class, it's been associated with weight gain and dyslipidemia (excess of triglycerides in the blood) and carries a black-box warning for stroke risk in elderly people. Plus, experts aren't quite clear on whether there's strong evidence to support the use of quetiapine for these off-label uses. In fact, in 2010, the drug's manufacturer agreed to pay a $520 million fine for allegations of promoting off-label prescriptions, mostly in low doses of 25 mg. for such as anger management, dementia and sleeplessness. The usual therapeutic dose range for the approved indications of schizophrenia or bipolar disorder is 400 to 800 mg. per day [Brett].

One of the study's authors said that in his clinical experience, "there's no report in the literature showing either that it's efficacious or really that it's safe in those low [25 mg.] doses" [source: Busko].

What It Is: Cyclic antidepressant

What It's Approved to Treat: Depression

Common Off-label Uses: Sleep problems

Trazodone works by stimulating serotonin in the brain, but it's not a selective serotonin reuptake inhibitor (SSRI) like other well-known antidepressants such as fluoxetine (Prozac). The drug was originally approved by the FDA in 1981 to treat depression, but because it causes drowsiness, it's actually become one of the most commonly used sleep medications. The drug still isn't FDA-approved to treat insomnia, however, and not much research has been done to support its long-term effectiveness or safety.

Because of the intense drowsiness it can cause, trazodone isn't commonly prescribed to treat depression alone anymore, but doctors continue to prescribe it as a lower-cost alternative to sleep medications like zolpidem (Ambien) and eszopiclone (Lunesta).

Many experts believe trazodone is safer than traditional sleep medications and less likely to result in impaired abilities or dependence, but the medication does have its own risks: It's more likely than newer sleep medications to leave users feeling drowsy the next day, and it can cause abnormally low blood pressure, dizziness, or fainting, especially in elderly patients [source: Consumer Reports].

What It Is: A class of drugs that blocks the neurotransmitters norepinephrine and epinephrine from binding to receptors.

What It's Approved to Treat: Heart problems, diabetes, hypertension

Common Off-label Uses: Migraine headaches, generalized anxiety disorder, hyperthyroidism, fibromyalgia, glaucoma, Parkinsonian tremor, atrial fibrillation

Beta blockers, including drugs like acebutolol (Sectral), atenolol (Tenormin) and bisoprolol (Zebeta), work on the beta receptors in the tissues of the body's sympathetic (i.e. "fight or flight") nervous system to inhibit hormones like epinephrine and norepinephrine that are considered stimulating. Doctors have been using them since the early 1960s to treat and prevent heart attacks and reduce blood pressure.

However, because these drugs act on hormones like epinephrine (otherwise known as adrenaline) and cortisol, they can mitigate the physical symptoms associated with these hormones like rapid heart rate, muscle tension and sweating. By preventing stimulating hormones from binding to their designated receptors in the body, those associated physical symptoms of stress simply go away.

Doctors sometimes favor beta blockers over approved anti-anxiety medications because they don't carry any risk of dependence, they're reasonably inexpensive and they have such a profound effect on the physical feelings of panic.

There are, however, potential downsides too: They're not effective for everyone, and one of the long-term side effects is a higher risk of developing Type 2 diabetes. The drugs also don't address the root cause of anxiety; just the symptoms. And long-term users trying to quit the medication could face severe withdrawal symptoms like blood pressure spikes and increased heart rate [source: Mental Health Daily].

What It Is: A phosphodiesterase (PDE) inhibitor

What It's Approved to Treat: Erectile dysfunction in men or to improve the ability to exercise in adults with pulmonary arterial hypertension

Common Off-label Uses: Enhancing sexual performance in people not diagnosed with erectile dysfunction, improving sexual function in women taking certain antidepressants

CNN called it "the little blue pill that could," and Viagra has certainly made a name for itself over the last two decades. In 1989, Pfizer scientists introduced a drug called sildenafil citrate that they anticipated would help treat high blood pressure and a type of chest pain associated with coronary heart disease called angina. During the drug's clinical trials, volunteers began reporting increased erections several days after taking a dose, and in 1998, the FDA approved the use of Viagra to treat erectile dysfunction [source: Wilson].

A decade later, scientists began finding evidence that the little blue pill could potentially help some women experiencing sexual dysfunction, too. Between 30 to 70 percent of people taking antidepressants experience sexual dysfunction, and a Pfizer-funded study found that seven out of nine women on antidepressants who had problems achieving orgasm recovered when they took Viagra [source: Carollo].

Female sexual response is complicated, and the FDA hasn't approved Viagra for this use in women, but another prescription medication called flibanserin (Addyi), originally developed as an antidepressant, is FDA-approved to treat low sexual desire in premenopausal women [source: Tobah].