32.2 Anorexiants

Anorexiants in Weight Management

Anorexiants are appetite suppressants used alongside diet and exercise to help patients lose weight. They work by acting on the central nervous system to reduce hunger and increase feelings of fullness. For nursing practice, understanding their mechanisms, side effects, and key interactions is critical because these drugs require careful patient selection and ongoing monitoring.

Key Features and Mechanisms of Action

Anorexiants reduce appetite through different CNS pathways depending on the specific drug. Here's how the major ones work:

• Phentermine (Adipex-P, Lomaira) stimulates the release of norepinephrine in the brain, which suppresses appetite. It also increases energy expenditure and promotes lipolysis (fat breakdown). Phentermine is a sympathomimetic amine, so think of it as revving up the sympathetic nervous system.
• Lorcaserin (Belviq) selectively activates serotonin 2C receptors in the hypothalamus, which increases satiety and decreases food intake. Note: the FDA requested voluntary withdrawal of lorcaserin from the U.S. market in 2020 due to cancer risk findings in a clinical trial. You may still see it on exams, but know its current status.
• Naltrexone/Bupropion (Contrave) is a combination drug. Naltrexone is an opioid antagonist that blocks opioid receptors involved in the reward response to eating. Bupropion is an antidepressant that increases dopamine and norepinephrine, which suppresses appetite and raises energy expenditure. Together, they target both the reward and hunger pathways.

Therapeutic Benefits, Side Effects, and Interactions

Benefits

When combined with a reduced-calorie diet and increased physical activity, anorexiants can produce clinically meaningful weight loss. A realistic goal is about 5–10% of initial body weight. That amount of loss can significantly improve obesity-related comorbidities like hypertension, dyslipidemia, and type 2 diabetes.

Side Effects

Each drug has a distinct side effect profile to know:

• Phentermine: dry mouth, insomnia, constipation, irritability, increased heart rate and blood pressure (remember, it's a sympathomimetic)
• Lorcaserin: headache, dizziness, fatigue, nausea, constipation
• Naltrexone/Bupropion: nausea (most common, especially early in treatment), constipation, headache, vomiting, dizziness

Drug Interactions

These interactions are high-yield for exams and clinical safety:

• Phentermine
  • With MAOIs: risk of hypertensive crisis. Phentermine should not be given within 14 days of MAOI use.
  • With serotonergic drugs: potential for serotonin syndrome.
• Lorcaserin
  • With serotonergic drugs (SSRIs, SNRIs, triptans): increased risk of serotonin syndrome.
  • With CYP2D6 inhibitors: may raise lorcaserin levels, increasing side effects.
• Naltrexone/Bupropion
  • With MAOIs: contraindicated due to risk of hypertensive reaction. Requires a 14-day washout.
  • With CYP2B6 inducers (e.g., ritonavir, carbamazepine): may decrease bupropion levels, reducing effectiveness.
  • Opioid analgesics: naltrexone blocks opioid receptors, so it will reduce or eliminate the effect of opioid medications. Patients must not be on opioids or in acute opioid withdrawal.

Nursing Considerations

Assessment

• Obtain a thorough medical history, including psychiatric history and any history of substance abuse (especially relevant for phentermine, which has abuse potential).
• Measure baseline weight, BMI, vital signs, and labs (fasting lipids, fasting glucose or $\text{HbA1c}$).

Patient Selection

Anorexiants are indicated for patients with:

• BMI ≥ 30, or
• BMI ≥ 27 with at least one weight-related comorbidity (hypertension, type 2 diabetes, dyslipidemia)

Review contraindications before starting therapy. Key ones include pregnancy, uncontrolled hypertension, glaucoma (phentermine), seizure disorders (bupropion component of Contrave), and significant cardiovascular disease history.

Monitoring

• Regularly reassess weight, BMI, and vital signs at follow-up visits.
• Watch for adverse effects specific to each drug.
• With phentermine, monitor for signs of abuse, dependence, or tolerance (it's a Schedule IV controlled substance and typically approved only for short-term use of up to 12 weeks).
• With naltrexone/bupropion, monitor mood and behavior changes, particularly suicidal ideation (bupropion carries a black box warning).

Patient Education Plan

• Provide clear instructions on dosage, how to take the medication (e.g., phentermine is typically taken in the morning to avoid insomnia), and expected treatment duration.
• Reinforce that medication alone is not enough. A reduced-calorie diet and regular physical activity are essential for results and for maintaining weight loss after the drug is discontinued.
• Set realistic expectations: a goal of 5–10% loss of initial body weight is considered clinically significant.
• Teach patients to recognize and report warning signs:
  • Serotonin syndrome: agitation, confusion, rapid heart rate, elevated temperature, muscle rigidity
  • Hypertensive crisis: severe headache, chest pain, vision changes, nosebleed
• Remind patients not to share medications with others, and to store and dispose of them properly (especially phentermine, given its controlled status).
• Stress the importance of keeping follow-up appointments so the care team can track progress, adjust dosing, and catch adverse effects early.
• Anorexiants are not a long-term cure for obesity. Lifestyle changes are what sustain weight loss after medication is stopped.