Commonly Used Medical Weight Loss Prescription Medications

Phentermine is an appetite suppressant that works by affecting the central nervous system, reducing hunger, and promoting feelings of fullness. It is typically taken once daily, either alone or in combination with other weight loss medications. However, this medication is not appropriate for everyone. Individuals with cardiac arrhythmias (fast or irregular heartbeats), uncontrolled high blood pressure, substance use disorders, severe anxiety, or those at high risk for stroke or heart attack may not be candidates for phentermine.

Phentermine is FDA-approved for short-term weight management — typically prescribed for 3 to 6 months at a time, followed by a 3 to 6-month break. It is classified by the DEA as a Schedule IV controlled substance, indicating a low to moderate potential for abuse. In other words, while effective, phentermine can be habit-forming after extended use, which is why it is prescribed in limited durations. Many patients also develop a tolerance after a few months, meaning the appetite-suppressing effects are strongest in the first 2–3 months and tend to diminish over time.

Common side effects — most noticeable in the first few days of use — may include:

• Dry mouth

• Constipation (often due to reduced food intake)

• Palpitations or tachycardia

• Elevated blood pressure

• Insomnia

• Mood changes

• Dehydration

Most patients report experiencing dry mouth. A significant number also require melatonin or another sleep aid to manage insomnia. Constipation is often managed with magnesium supplementation (adjusted as needed) and stool softeners.

At Pure Medicine, Dr. Pastorek requires monthly visits while patients are taking phentermine due to its controlled status. These visits allow for close monitoring of weight loss progress, vital signs, and management of any side effects. Many patients opt for telemedicine check-ins, provided they can record and submit their blood pressure, pulse, and weight from home.

Depending on a patient’s risk factors, additional cardiac clearance may be required. This could include an EKG, calcium scoring, stress testing, or blood pressure logs, and in some cases, an official clearance from a cardiologist.

If phentermine is not an appropriate option, other medical weight loss alternatives are available and can be discussed with Dr. Pastorek.

While taking phentermine, Dr. Pastorek typically recommends:

• An 800–1,000 calorie/day diet (made more manageable with the medication)

• Daily weigh-ins

• Food logging (using apps like MyFitnessPal)

• A 20-minute walk on non-exercise days

• Gradual increases in moderate-intensity exercise

Building sustainable exercise habits is highly encouraged, as increasing physical activity plays a key role in preventing weight regain once the medication is discontinued.

Like phentermine, phendimetrazine acts as an appetite suppressant by stimulating the central nervous system to help reduce calorie intake.

Phendimetrazine is a shorter-acting medication, so unlike phentermine (which is typically taken once daily), it is prescribed to be taken three times daily — usually before meals.

Phendimetrazine is classified by the DEA as a Schedule III controlled substance, meaning it has a moderate potential for abuse.

Dr. Pastorek may switch patients from phentermine to phendimetrazine after several months of phentermine use, especially if weight loss plateaus due to tolerance. One of the advantages of phendimetrazine is that it is taken before each meal and offers strong appetite suppression about an hour after dosing. However, the downside is that many patients struggle to remember the midday and/or evening doses — and when a dose is missed, appetite tends to return quickly.

That said, phendimetrazine can be an effective tool for breaking through plateaus or shedding the final few pounds at the end of a weight loss program when phentermine’s effectiveness has declined.

The side effects and restrictions of phendimetrazine are very similar to those of phentermine (see above).

Semaglutide is a once-weekly injectable medication that mimics a natural hormone in the body to help regulate blood sugar and reduce appetite. It has gained widespread recognition for its potential to promote significant weight loss—so much so that supply chain issues have occurred several times over the past year.

Wegovy and Ozempic are both brand names for semaglutide, produced by the same pharmaceutical company, Novo Nordisk A/S, and are virtually the same medication.

Mounjaro is currently FDA-approved only for the treatment of Type 2 diabetes. However, Zepbound — which also contains tirzepatide — is a newer medication that has been FDA-approved specifically for weight loss.

Unlike semaglutide (Wegovy/Ozempic), which mimics a single hormone, Mounjaro/Zepbound (tirzepatide) mimics two hormones that help regulate blood sugar and reduce appetite.

According to clinical studies, tirzepatide results in slightly greater weight loss over approximately one year compared to semaglutide (Wegovy/Ozempic).

Most insurance plans will only cover Mounjaro for patients with Type 2 diabetes. Due to its high cost, many insurers require patients to try and fail less expensive alternatives before approving it. While Zepbound is FDA-approved for weight loss, insurance coverage varies, and not all plans currently include it.

Side effects of Mounjaro/Zepbound are similar to those of semaglutide and may include nausea, gastrointestinal discomfort, and reduced appetite. The recommended dietary plan for tirzepatide use is also similar to the one followed by patients on semaglutide.

Tirzepatide is also available through some compounding pharmacies, though it is currently more difficult to source than semaglutide. The cost is typically around $500 per month, nearly double the cost of compounded semaglutide.

Contraindications for Tirzepatide:

• A personal history of medullary thyroid carcinoma (MTC)

• A family history of multiple endocrine neoplasia syndrome type 2 (MEN 2)

• A history of chronic pancreatitis

Qsymia is a combination medication that contains phentermine and topiramate.

While phentermine works by suppressing appetite, topiramate helps reduce food cravings — making this combination effective for comprehensive appetite control.

Qsymia is often prescribed for patients who have difficulty tolerating the side effects of full-dose phentermine (such as rapid heart rate, palpitations, insomnia, or elevated blood pressure). It allows for a lower dose of phentermine (typically 7.5–15 mg compared to 37.5 mg), which reduces the likelihood and severity of side effects.

The addition of topiramate augments the effects of the lower phentermine dose, helping patients achieve weight loss results similar to full-dose phentermine, but with a significantly milder side effect profile.

Because Qsymia contains phentermine, it is classified by the DEA as a Schedule IV controlled substance, indicating a low to moderate potential for abuse. While taking Qsymia, Dr. Pastorek requires monthly follow-up visits (in-office or via telemedicine) to monitor vital signs, treatment effectiveness, and potential side effects.

Qsymia can often be used longer than standalone phentermine due to the reduced phentermine dose; however, it is not typically intended for indefinite use.

Side effects are similar to those associated with phentermine (see phentermine), though they tend to be much less pronounced due to the lower dosage.

Cost can be a consideration — approximately $500 per month — but manufacturer discounts and insurance coverageoften help offset the price. Additionally, a similar dosing regimen using generic phentermine and topiramate may reduce costs to under $100 per month.

This medication was initially developed as an anti-seizure drug and is also used to treat migraines. It has also been found to aid in weight loss, specifically when combined with other medications like phentermine, by reducing appetite and increasing feelings of fullness (See Qsymia).

Contrave is a combination medication that includes bupropion and naltrexone, working together to target the brain’s reward system and help control cravings. It is especially effective for those struggling with emotional eating or binge eating behaviors.

This medication can be used long-term and typically results in gradual, sustained weight loss over time.

Bupropion is a commonly prescribed antidepressant, also marketed under the brand name Zyban for smoking cessation.

Naltrexone is used to block opioid receptors. Because of this, Contrave is contraindicated for individuals who take opioid pain medications, as naltrexone will block their effects, rendering them ineffective. By dampening dopamine surges that occur with stress or reward-based eating, naltrexone helps reduce the pleasurable “sugar high” often associated with emotional or binge eating.

Patients with chronic pain who are taking opioids should not use Contrave.

As with any medication that affects mood and brain chemistry, if you experience worsening depression or suicidal thoughts while taking Contrave, stop the medication immediately and contact your doctor.