Pharmacology for Nurses Unit 32 Review: Weight Management Drugs

Introduction to Weight Management Drugs

• Weight management drugs assist individuals in achieving and maintaining a healthy weight when combined with lifestyle modifications (diet and exercise)
• These medications work by altering appetite, metabolism, or absorption of nutrients to promote weight loss
• Commonly prescribed for patients with a body mass index (BMI) ≥30 or ≥27 with weight-related comorbidities (hypertension, type 2 diabetes)
• Not intended as a standalone treatment but rather as an adjunct to comprehensive weight management programs
• Require close monitoring by healthcare professionals to assess efficacy, safety, and potential side effects
• May be used short-term or long-term depending on the specific drug and patient's needs
• Offer a valuable tool for managing obesity and its associated health risks when used appropriately under medical supervision

Mechanisms of Action

• Weight management drugs target various pathways in the body to promote weight loss
• Appetite suppressants (phentermine) act on the central nervous system to reduce hunger and increase feelings of fullness
  • Stimulate the release of norepinephrine, a neurotransmitter that signals satiety
  • Decrease appetite by influencing the hypothalamus, the brain region responsible for regulating hunger
• Lipase inhibitors (orlistat) decrease the absorption of dietary fat in the intestines
  • Block the action of pancreatic lipase, an enzyme that breaks down triglycerides
  • Undigested fat is eliminated from the body, reducing caloric intake
• Glucagon-like peptide-1 (GLP-1) receptor agonists (liraglutide) mimic the effects of the hormone GLP-1, which regulates appetite and glucose metabolism
  • Slow gastric emptying, leading to increased feelings of fullness and reduced food intake
  • Stimulate insulin secretion and inhibit glucagon release, helping to control blood sugar levels
• Combination medications (phentermine/topiramate) employ multiple mechanisms to enhance weight loss
  • Phentermine suppresses appetite while topiramate increases feelings of fullness and alters taste perception
• Some drugs (bupropion/naltrexone) target the brain's reward system to reduce cravings and overeating behaviors

Common Weight Management Drugs

• Phentermine (Adipex-P, Lomaira) is a sympathomimetic amine that suppresses appetite
  • Approved for short-term use (up to 12 weeks) in conjunction with lifestyle modifications
  • Available as tablets or capsules in various strengths (8 mg, 15 mg, 30 mg, 37.5 mg)
• Orlistat (Xenical, Alli) is a lipase inhibitor that reduces fat absorption
  • Xenical is a prescription medication, while Alli is available over-the-counter at a lower dose
  • Taken with each main meal containing fat, up to three times daily
• Liraglutide (Saxenda) is a GLP-1 receptor agonist administered as a daily subcutaneous injection
  • Approved for long-term weight management in adults with a BMI ≥30 or ≥27 with at least one weight-related comorbidity
  • Initiated at a dose of 0.6 mg per day and titrated up to 3 mg per day
• Phentermine/topiramate (Qsymia) is a combination medication available in four dose strengths
  • Recommended to start at the lowest dose (3.75 mg/23 mg) and titrate up based on response and tolerability
• Bupropion/naltrexone (Contrave) combines an antidepressant and an opioid antagonist to target the brain's reward system
  • Supplied as extended-release tablets taken twice daily
  • Dosage is gradually increased over several weeks to minimize side effects

Indications and Contraindications

• Weight management drugs are indicated for adults with a BMI ≥30 or ≥27 with at least one weight-related comorbidity (hypertension, dyslipidemia, type 2 diabetes)
  • Should be used in conjunction with a reduced-calorie diet and increased physical activity
  • Continued use is recommended only if the patient achieves and maintains at least 5% weight loss after 12 weeks of treatment
• Contraindications vary depending on the specific drug and its mechanism of action
• Phentermine is contraindicated in patients with a history of cardiovascular disease, hyperthyroidism, glaucoma, or monoamine oxidase inhibitor (MAOI) use
  • Should not be used during pregnancy due to the potential for fetal harm
• Orlistat is contraindicated in patients with chronic malabsorption syndrome or cholestasis
  • Not recommended for use in patients with a history of oxalate nephrolithiasis or hyperoxaluria
• Liraglutide is contraindicated in patients with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2
  • Should not be used in combination with other GLP-1 receptor agonists or insulin
• Phentermine/topiramate is contraindicated in patients with glaucoma, hyperthyroidism, or MAOI use
  • Should not be used during pregnancy due to the potential for fetal harm (oral cleft defects)
• Bupropion/naltrexone is contraindicated in patients with uncontrolled hypertension, seizure disorders, or anorexia nervosa
  • Should not be used in patients undergoing abrupt discontinuation of alcohol, benzodiazepines, or antiepileptic drugs

Dosing and Administration

• Dosing and administration guidelines vary depending on the specific weight management drug
• Phentermine is typically prescribed at a dose of 15-37.5 mg once daily, taken before breakfast or 1-2 hours after breakfast
  • Available as tablets or capsules in various strengths (8 mg, 15 mg, 30 mg, 37.5 mg)
  • Should not be used for more than 12 weeks due to the potential for abuse and dependence
• Orlistat (Xenical) is prescribed at a dose of 120 mg three times daily, taken with each main meal containing fat
  • Patients should take a multivitamin supplement at least 2 hours before or after orlistat to prevent deficiencies in fat-soluble vitamins
• Liraglutide (Saxenda) is initiated at a dose of 0.6 mg per day, administered as a subcutaneous injection
  • Dose is increased by 0.6 mg weekly until the maintenance dose of 3 mg per day is reached
  • Injections can be given at any time of day, with or without meals
• Phentermine/topiramate (Qsymia) is available in four dose strengths: 3.75 mg/23 mg, 7.5 mg/46 mg, 11.25 mg/69 mg, and 15 mg/92 mg
  • Treatment is initiated at the lowest dose and titrated up based on response and tolerability
  • Tablets should be taken once daily in the morning, with or without food
• Bupropion/naltrexone (Contrave) is supplied as extended-release tablets, each containing 8 mg of naltrexone and 90 mg of bupropion
  • Dosing is initiated with one tablet daily and gradually increased over several weeks to the maintenance dose of two tablets twice daily
  • Tablets should be taken with meals and swallowed whole, not crushed or chewed

Side Effects and Adverse Reactions

• Weight management drugs can cause various side effects and adverse reactions, some of which may be severe
• Common side effects of phentermine include dry mouth, insomnia, constipation, and increased heart rate
  • More serious adverse reactions may include hypertension, palpitations, and psychosis
• Orlistat frequently causes gastrointestinal side effects such as oily spotting, flatulence, and fecal urgency
  • May also lead to malabsorption of fat-soluble vitamins (A, D, E, K) and rare cases of severe liver injury
• Liraglutide can cause nausea, vomiting, diarrhea, and constipation
  • Serious adverse reactions include pancreatitis, gallbladder disease, and increased risk of thyroid C-cell tumors
• Phentermine/topiramate may cause paresthesia, dizziness, dysgeusia, and insomnia
  • Rare but severe side effects include metabolic acidosis, kidney stones, and increased heart rate
• Bupropion/naltrexone commonly causes nausea, constipation, headache, and dry mouth
  • Serious adverse reactions may include seizures, angle-closure glaucoma, and increased blood pressure or heart rate
• Patients should be monitored closely for the development of side effects and adverse reactions
  • Dosage adjustments or discontinuation of therapy may be necessary if severe or intolerable side effects occur

Drug Interactions

• Weight management drugs can interact with various medications, potentially altering their efficacy or increasing the risk of adverse reactions
• Phentermine may interact with MAOIs, serotonergic drugs (SSRIs, SNRIs), and sympathomimetic agents (decongestants, stimulants)
  • Concomitant use can lead to hypertensive crisis, serotonin syndrome, or increased cardiovascular risk
• Orlistat may reduce the absorption of cyclosporine, levothyroxine, and anticonvulsants (valproic acid, lamotrigine)
  • Separate administration of these medications by at least 2 hours to minimize interactions
• Liraglutide can delay gastric emptying, potentially affecting the absorption of concomitantly administered oral medications
  • Monitor patients closely when initiating or discontinuing liraglutide treatment
• Phentermine/topiramate may interact with oral contraceptives, reducing their efficacy
  • Patients should use a non-hormonal method of contraception during treatment and for several months after discontinuation
• Bupropion/naltrexone can interact with MAOIs, opioids, and dopaminergic drugs (levodopa, amantadine)
  • Concomitant use may increase the risk of hypertension, seizures, or serotonin syndrome
• Healthcare professionals should review patients' medication lists carefully to identify potential drug interactions
  • Dose adjustments, alternative therapies, or increased monitoring may be necessary to manage interactions safely

Patient Education and Monitoring

• Patient education is crucial for the safe and effective use of weight management drugs
• Patients should be informed about the expected benefits, potential side effects, and proper administration of their prescribed medication
  • Emphasize the importance of adhering to the recommended dosage and administration schedule
  • Advise patients to report any adverse reactions or concerns to their healthcare provider promptly
• Encourage patients to adopt lifestyle modifications (reduced-calorie diet, regular physical activity) in conjunction with pharmacotherapy
  • Set realistic weight loss goals and provide resources for long-term weight management support
• Educate patients on the signs and symptoms of serious adverse reactions (e.g., pancreatitis, hypertensive crisis) and when to seek immediate medical attention
• Regularly monitor patients' weight, BMI, and vital signs to assess the efficacy and safety of the prescribed medication
  • Adjust dosage or discontinue therapy if the patient fails to achieve or maintain at least 5% weight loss after 12 weeks of treatment
• Perform periodic laboratory tests to monitor for potential adverse effects (liver function tests, lipid profile, blood glucose)
  • Screen for the development of comorbidities (hypertension, type 2 diabetes) and provide appropriate interventions
• Assess patients' mental health and monitor for changes in mood, anxiety, or suicidal ideation
  • Consider referral to a mental health professional if significant psychological distress is observed
• Provide ongoing support and encouragement to help patients maintain their weight loss and adopt healthy lifestyle habits
  • Regularly review and adjust the weight management plan based on the patient's progress and individual needs