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Can Prescription Drugs Cause Weight Gain?

Medically reviewed on Feb 24, 2014 by L. Anderson, PharmD

Losing weight, or maintaining a healthy weight, can be a battle for many patients. Roughly 70 percent of people in the U.S. are over their ideal body weight or exceed their recommended body mass index (BMI). Aging, lack of exercise, and diet changes are all culprits in the battle to keep weight down. Some very common medications can also lead to weight gain - prescription drugs used for mood disorders, diabetes, high blood pressure and seizures can all add on unwanted pounds. While some medications are more common than others to add pounds, not all patients gain weight from every drug that has weight gain listed as a side effect.

How Do Prescription Drugs Cause Weight Gain?

For many drugs, it is not known exactly what causes the weight gain. Some medications can increase appetite, cause fluid retention, or slowly lead to weight gain over a period of time due to fatigue and lower activity. Drugs that trigger increases in appetite may work in the brain and affect the satiety (fullness) center.  It is often difficult to distinguish between weight gain from a drug and weight gain from other reasons, like diet or lack of exercise, because it can be a slow process. Weight gain may increase the chance for high cholesterol, hypertension (high blood pressure), and type 2 diabetes. If a rapid weight gain occurs in a short period of time, a physician should be contacted for evaluation, especially if the patient is at risk for heart disease or high blood pressure.

Patients should not stop taking any medication without talking to their doctor. Some drugs will need to be slowly tapered, and an abrupt discontinuation may lead to side effects. If a patient has a concern about weight gain with a medication, they should discuss this topic with their physician. The patient may be able to switch to a different medication or use a lower dose. In many cases, patients will need to increase their level of exercise, as well. Patients should also ask their healthcare provider about the potential for weight gain before a new medication is prescribed. Alternative treatments may be available. And remember, medications may affect patients differently, and not every patient will gain weight.

What Drugs Can Lead to Weight Gain?

  • Antidepressants: Older antidepressants, known as tricyclic antidepressants (TCAs) are notorious for increasing appetite and causing weight gain. Examples of TCAs include amitriptyline (Elavil) and nortriptyline (Pamelor). TCAs affect neurotransmitters in the brain and exhibit antihistaminic activity, which can boost appetite. TCAs may also be used to treat migraine headaches. A newer class of antidepressants, called selective serotonin reuptake inhibitor (SSRI) are not usually associated with weight gain, but one of the frequently prescribed SSRIs, paroxetine (Paxil) has been linked to weight gain. Some SSRIs are more weight neutral, such as fluoxetine (Prozac) or sertraline (Zoloft). Mirtazapine (Remeron) is an antidepressant that boosts serotonin, like SSRIs, but also has an antihistamine effect that may lead to weight gain. Usually, a physician can choose among many alternatives in the antidepressant class if weight gain is an issue. Bupropion (Wellbutrin) is antidepressant that is actually associated with weight loss. Venlafaxine (Effexor) and duloxetine (Cymbalta) also have more neutral effects on weight gain.
  • Antihistamines: Antihistamines, such as cetirizine (Zyrtec) and fexofenadine (Allegra), selectively antagonize histamine H1 receptors. These drugs, which are available without a prescription, have been associated with weight gain. Antihistaminic activity can boost appetite, as noted with several other drugs that cause weight gain. A study published in 2010 compared the use of antihistamines and the risk of obesity. Users of cetirizine and fexofenadine has a significantly greater weight, BMI, waist circumference, and insulin levels.1
  • Antipsychotics/Mood Disorder: Some antipsychotics are frequently linked with weight gain. Example drugs in this class include the atypical antipsychotics olanzapine (Zyprexa) and risperidone (Risperdal). Clozapine (clozaril), an older, atypical antipsychotic has also been linked with significant weight gain. Patients can gain from seven to ten percent of their body weight. These drugs may have antihistaminic activity and also block serotonin, which may contribute to the mechanism of weight gain. Research has shown an enzyme called AMP-kinase is elevated in the brain of patients who use antipsychotics. AMP-kinase can block the brain histamine-1 receptor, which will boost appetite and may lead to weight gain.2 Many of the antipsychotics may impair glucose (sugar) control and lead to insulin resistance, impaired glucose tolerance and type 2 diabetes. However, these drugs may be necessary for treatment of bipolar disorder or schizophrenia, and patients must speak with their physician before stopping treatment. A fasting blood glucose should be checked at the beginning of antipsychotic treatment and periodically thereafter. Ziprasidone (Geodon) and aripiprazole (Abilify) are more weight neutral antipsychotics, but still may cause alter blood glucose.
  • Antihypertensives - Beta Blocker (Blood Pressure): The class of high blood pressure drugs known as beta blockers have been associated with weight gain. Common examples of this class are metoprolol (Lopressor) and atenolol (Tenormin). Many of the older beta blocker drugs can lead to fatigue, which may be responsible for some of the weight gain. Patients may be tired, have lack of energy, and in general slow down, which may affect the number of calories burned each day.1
  • Corticosteroids: Oral corticosteroids (glucocorticoids) may carry a risk of weight gain with high dose and long-term use. Oral corticosteroids are used for severe asthma, or painful inflammatory conditions such as arthritis. Local injectable corticosteroids, such as might be done in the knee joint or spine column for inflammation, and inhaled corticosteroids used for asthma are not associated with weight gain. Steroids can affect the metabolic rate, and lead to increased appetite and overeating. Examples of corticosteroids include prednisone, methylprednisolone, and hydrocortisone.
  • Diabetes Medications: Certain oral medications for type 2 diabetes, such as glyburide (DiaBeta) and glipizide (Glucotrol), members of the sulfonylurea class, can lead to weight gain. These agents may increase insulin production, which can lower blood sugar levels and result in an elevated appetite. Injectable insulin itself can also lead to weight gain, possibly due to periods of low blood sugar that stimulate appetite. Other drugs used in the treatment of type 2 diabetes can lead to weight gain and fluid retention. Examples include pioglitazone (Actos) and rosiglitazone (Avandia) which are in the class thiazolidinediones. Metformin (Glucophage), exenatide (Byetta), and sitagliptin (Januvia) are more likely to be weight neutral or associated with weight loss.
  • Seizures/Mood Stabilizers: Valproic acid (Depakote, Depakene) is used to treat epilepsy (seizures), bipolar disorder and for migraine prevention. Valproic acid appears to boost appetite and may result in a 10 pound or more weight gain. Lithium (Lithobid) is also used for mood disorders, and is associated with weight gain.

Common Drugs That May Lead to Weight Gain

Medication Generic Name Drug Class or Use
Paxil Paroxetine SSRI Antidepressant
Zoloft Sertraline SSRI Antidepressant
Elavil Amitriptyline Tricyclic Antidepressant
Remeron Mirtazapine Antidepressant
Clozaril Clozapine Antipsychotic/Mood Stabilizer
Zyprexa Olanzapine Antipsychotic/Mood Stabilizer
Risperdal Risperidone Antipsychotic/Mood Stabilizer
Seroquel Quetiapine Antipsychotic/Mood Stabilizer
Lithobid Lithium Mood Stabilizer
Depakene, Depakote Valproic acid, divalproex Seizure Disorder/Migraines/Mood Stabilizer
Neurontin Gabapentin Seizure Disorder
Tegretol Carbamazepine Seizure Disorder/Mood Disorder
Lopressor Metoprolol Antihypertensive-Beta Blocker (blood pressure)
Tenormin Atenolol Antihypertensive-Beta Blocker (blood pressure)
Inderal Propranolol Antihypertensive-Beta Blocker (blood pressure)
Norvasc Amlodipine Antihypertensive-Beta Blocker (blood pressure)
Catapres Clonidine Alpha-2 Adrenergic Agonist (blood pressure,
Actos Pioglitazone Thiazolidinediones (diabetes)
Avandia Rosiglitazone Thiazolidinediones (diabetes)
Amaryl Glimepiride Sulfonylureas (diabetes)
Novolog, Lantus, Humalog (various brands) Insulin Diabetes
Diabeta Glyburide Sulfonylureas (diabetes)
Glucotrol Glipizide Sulfonylureas (diabetes)
Deltasone, Medrol, Solu-Cortef oral prednisone, oral methylprednisolone, hydrocortisone injectable Corticosteroid
Allegra fexofenadine Antihistamines
Zyrtec cetirizine Antihistamines

Tables sourced from ref. 3,4.

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  1. Ratliff JC, Barber JA, Palmese LB, et al. Association of Prescription H1 Antihistamine Use With Obesity: Results From the National Health and Nutrition Examination Survey. Obesity 2010;18:2398-2400.
  2. Kim S, Huang A, Snowman A, et al. Antipsychotic drug-induced weight gain mediated by histamine H1 receptor-linked activation of hypothalamic AMP-kinase. Proceedings of the National Academies of Sciences. 2007;104:3456-59.
  3. Cheskin L. (June, 2011) Prescription drugs that can cause weight gain. John Hopkins Health Alert. Accessed November 18, 2012.
  4. (March 2012) Prescription Meds Can Put on Unwanted Pounds. Accessed online November 18, 2012.