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Weight loss medications: Nursing Pharmacology



benzphetamine hydrochloride (Didrex), diethylpropion hydrochloride (Tenuate)
(Xenica, Alli)
phentermine (Ionamin)
Lipase inhibitors
Sympathomimetic medications
↑ release of norepinephrine and dopamine in the satiety center →
↓ appetite

Inhibit fat absorption in the GI tract

↓ reuptake of norepinephrine and dopamine  
→ ↑ concentration of norepinephrine and dopamine in the synaptic cleft
 → ↓  perception of hunger

  • PO
  • Agitation 
  • Anxiety
  • Irritability
  • Insomnia
  • Heart palpitations
  • Systemic or pulmonary hypertension
  • Valvular heart disease

  • Oily spotting 
  • Steatorrhea 
  • Flatus with discharge 
  • Fecal urgency or incontinence 
  • Headache 
  • Nausea, vomiting, abdominal cramping 
  • Acute liver failure 
  • Hypoglycemia in clients  with diabetes

  • Hyperactivity 
  • Irritability 
  • Insomnia 
  • Tachycardia 
  • Heart palpitations 
  • Hypertension 
  • Arrhythmias 
  • Gastrointestinal side effects: 
    • nausea
    • vomiting
    • diarrhea
    • constipation
(Saxenda, Victoza)
naltrexone/bupropion (Contrave)
GLP-1 receptor agonists
Opioid antagonists & Atypical antidepressants
  • Slow gastric emptying → ↑ satiety after eating 
  • ↓ appetite


Stimulates POMC neurons in the hypothalamus to 

↑ release of hormones →  ↑ energy output & ↓ appetite


Binds to opioid receptors without activating them, → POMC neurons stay stimulated longer by bupropion 

  • Headaches 
  • Dizziness 
  • Weakness 
  • Nausea, vomiting 
  • Diarrhea 
  • Injection site reactions (pruritus) 
  • Renal impairment 
  • Acute pancreatitis 
  • Hypoglycemia (when combined with other anti-diabetic medications) 
  • Increased risk of thyroid cancer development
  • Tachycardia
  • Insomnia
  • Seizures
  • Boxed warning: Increased risk of suicidal thoughts

DRUG NAME(all drugs from parts 1&2)
benzphetamine hydrochloride (Didrex), diethylpropion hydrochloride (Tenuate, orlistat (Xenica, Alli), phentermine (Ionamin), liraglutide (Saxenda, Victoza), naltrexone/bupropion (Contrave)
  • Short-term management of obesity 
  • GLP-1 receptor antagonist: Diabetes mellitus type 2
  • Pregnancy, breastfeeding 
  • Elderly clients, children 
  • Arteriosclerosis, severe cardiovascular disease, moderate to severe hypertension 
  • History stroke or seizures 
  • Psychiatric conditions (e.g. anorexia nervosa, depression, bipolar disorder) 
  • Hyperthyroidism 
  • Glaucoma 
  • Hepatic or renal disease 
  • Tobacco smoking or substance abuse
NURSING CONSIDERATIONSAssessment and Monitoring


  • Current nutritional habits 
  • Vital signs 
  • Weight, BMI, waist circumference
  • Laboratory test results: renal and hepatic function, blood glucose, thyroid panel, lipid panel; negative pregnancy test for female clients 


  • Side effects
  • Hepatic function
  • Evaluate therapeutic response: decreased weight, BMI, waist circumference; optimal nutritional intake

Client Education 

  • Purpose of medication: to help with weight loss 
  • Used in combination with lifestyle modifications 
    • Regular physical activity as tolerated, decreased alcohol intake,
    • Reduced-calorie, low-fat diet that contains complex carbohydrates, fruits, vegetables, lean sources of protein
  • Self-administration 
    • Take three times each day with meals containing fat
      • With missed meals and meals containing no fat, do not take dose of medication
      • Take a prescribed multivitamin 2 hours before or after orlistat
      • Take multivitamin containing fat-soluble vitamins
  • Side effects: oily rectal leakage, steatorrhea, flatus, fecal urgency and incontinence 
  • Notify healthcare provider
    • Hepatotoxicity: nausea, anorexia, dark-colored urine, yellowing of the skin and eyes
    • Cholilithiasis: sudden abdominal pain that gets stronger, can be felt around their right shoulder or between their shoulder blades

Weight loss medications can be used for the short-term management of obesity, and include anorexiants, sympathomimetic medications, lipase inhibitors, glucagon-like peptide-1 or GLP-1 receptor agonists, as well as opioid antagonists combined with atypical antidepressants.

Starting with anorexiants, the most commonly used are benzphetamine and diethylpropion, which are taken orally. These medications are believed to decrease appetite by stimulating the release of dopamine and norepinephrine in the satiety center of the brain, which is located in the hypothalamic and limbic areas. As a result, these neurotransmitters ultimately increase the feeling of satiety and decrease the perception of hunger.

Then, there are sympathomimetic medications, among which the most commonly used one for weight loss is phentermine, which is taken orally. Once administered, phentermine is absorbed into the bloodstream, and travels to the brain.

Here, it works at the synaptic cleft by inhibiting the reuptake of the neurotransmitters dopamine and norepinephrine. This results in an increased concentration of these neurotransmitters within the synaptic cleft, ultimately decreasing the perception of hunger.

Moving on, lipase inhibitors include orlistat, which is taken orally. This medication acts in the gastrointestinal tract by inhibiting the absorption of fats, causing them to get excreted in the feces.

Next are GLP-1 receptor agonists, which are primarily used as oral antidiabetic medications, and mainly include liraglutide that is administered through subcutaneous injection. The way liraglutide works is by acting on the stomach to slow gastric emptying. This leads to an increase in the feeling of satiety after eating. In addition, this medication can act in the brain to suppress appetite.

Finally, weight loss medications include opioid antagonists like naltrexone, which is generally combined with an atypical antidepressant, namely bupropion. These medications are taken together orally.

The way bupropion works is by stimulating proopiomelanocortin or POMC neurons in the hypothalamus to release hormones that increase energy output and decrease appetite. Now, POMC neurons are inhibited by opioids.

So, then comes naltrexone, which binds strongly to opioid receptors without activating them, thereby letting POMC neurons stay stimulated longer by bupropion.

Now, clients taking weight loss medications can often experience side effects, which depends on the medication taken. Side effects commonly associated with anorexiants are agitation, anxiety, irritability, and difficulty sleeping. Less commonly, clients can also experience heart palpitations, systemic or pulmonary hypertension, as well as valvular heart disease.

Next, sympathomimetic medications like phentermine can often cause side effects like hyperactivity, irritability, and insomnia. Some clients may also experience gastrointestinal side effects, like nausea, vomiting, diarrhea or constipation.

Also, clients often develop tachycardia and palpitations, while some may present hypertension or even arrhythmias. Finally, it’s important to note that unlike other sympathomimetic medications, phentermine’s risk for potential abuse and dependence is considered insignificant.

On the other hand, side effects of lipase inhibitors include oily rectal leakage and steatorrhea, meaning fatty, greasy, floating, voluminous, and terribly smelling stools, often associated with flatus, fecal urgency or incontinence. Clients can also experience nausea, vomiting, or abdominal cramping, and some may even develop acute liver failure! In addition, clients with diabetes mellitus may present with hypoglycemia.

Now, the most common side effects of GLP-1 receptor agonists include headaches, dizziness, and weakness, associated with nausea, vomiting, and diarrhea. In addition, these medications can cause injection site reactions like pruritus, and less frequently, renal impairment and acute pancreatitis.

In addition, GLP-1 receptor agonists have a boxed warning for increasing the risk of thyroid cancer development. Finally, when combined with other anti-diabetic medications, GLP-1 receptor agonists can cause hypoglycemia.

The last weight loss medication are opioid antagonists combined with atypical antidepressants. Now, these opioid antagonists can cause side effects like dizziness, as well as abdominal pain, nausea, vomiting, diarrhea, and flatulence, while some clients can even present with gastrointestinal perforation.

On the other hand, due to their excitatory effects, atypical antidepressants can often cause vision and hearing disturbances, headaches, agitation, insomnia, dizziness, and confusion, as well as tremors, and even seizures, which is particularly important in clients with a history of seizures or eating disorders.

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