Drugs Used To Treat Obesity



Drugs Used To Treat Obesity

Obesity is define as the state in which an excess of fat accumulates in the body. Obesity is always the consequence of a disturbed energy balance: caloric intake exceeds consumption.

Body-Mass-Index (BMI) assesses relative body weight (kg) / body height2(m).

Normal values range from 22-28.

Values > 30 are indicative of an overweight condition.

Why Treat Obesity?

Excess body weight and obesity lead to diseases and a shortened lifespan.

The most important secondary disorders include:

• Type 2 diabetes mellitus.

• Hypertension, which together disturbed lipid metabolism gives rise to atherosclerosis.

• Effects on bone resulting in osteoarthritis and degenerative joint disease.

• Obesity gives rise to psychological problems.

Treatment

1. Food : “ eat much less, move much more”

Requisite changes include a diet low in fat with reduced caloric content (1000 kcal/day) and no snacks (sweets, potato chips, etc.)

2. Physical exercise (sports, hiking, swimming, etc.)

3. Weight loss medications.

4. Weight loss surgery.

Drugs Used To Treat Obesity

• These drugs used along with diet, exercise and behavior changes. Not instead of them.

• Weight loss medications reduce food consumption or reduce food absorption.

The categories of individuals who should be given priority in advice on how to lose weight should include:

1. Those with BMI > 30

2. Those with BMI > 25 who also have other cardiovascular risk factors.

3. Those with medical conditions that exacerbate by obesity.

4. Those who have abdominal distribution of fat.

Two classes of drugs are used in treating obesity:

1. The anorexiants (appetite suppressants) Phentermine, diethylpropion, and sibutramine

Phentermine and diethylpropion are indicated for short-term management of obesity.

While, sibutramine used for up to 2 years.

2. Lipase inhibitor: orlistat (up to 4 years of use).

A. Phentermine, diethylpropion, and sibutramine:

Phentermine acts by

• Increasing release of norepinephrine and dopamine from the nerve terminals.

• Inhibiting reuptake of these neurotransmitters (norepinephrine, dopamine) there by increasing levels of neurotransmitters in the brain.

Diethylpropion has similar effects on norepinephrine.

Sibutramine

• Inhibits central reuptake of serotonin, norepinephrine, and dopamine.

• Not cause the release of neurotransmitters.

• Increase blood pressure and should be avoided in patients with heart disease.

• Sibutramine is taken once daily with or without food.

• Should take in the morning to avoid insomnia.

Pharmacokinetics

• The duration of activity of phentermine is dependent on the formulation.

• Route of excretion of phentermine and diethylpropion and its metabolites is via the kidney.

• Diethylpropion is rapidly absorbed and undergoes extensive first-pass metabolism.

• Many of the metabolites are active (half-life is 4 to 8 hr.)

• Sibutramine undergoes first-pass demethylation to active metabolites, which are primarily responsible for its pharmacologic effects (half-life is about 15 hr.)

Adverse effects and contraindications

* All of the appetite suppressants have the potential for dependence or abuse.

* Dry mouth, headache, insomnia, and constipation are common problems.

* Heart rate and blood pressure may be increased.

* Phentermine has been associated with heart valve disorder and pulmonary hypertension.

* Should be avoided in hypertension, CVD, arrhythmias, congestive heart failure, or stroke.

* Concomitant use of appetite suppressants and MAOI should be avoided.

* Sibutramine should also be avoided in patients who are taking SSRI, and serotonin agonist for migraine such as sumatriptan

* Drug interactions can occur when sibutramine is administered with ketoconazole, erythromycin, and cimetidine.

B. Orlistat

Is the first drug in a class of antiobesity drugs known as lipase inhibitors Decreasing the breakdown of dietary fat into smaller molecules that can be absorbed, ingested fats are not hydrolyzed to fatty acids and glycerol; thus it is not absorbed and is excreted as fecal fat.

Fat absorption is decreased by about 30%. It is taken with meal of the 3 main meals of the day and the dose can be adjusted (60 -120 mg) to minimize side effects.

Adverse effects:

• GI symptoms: oily spotting, flatulence with discharge, fecal urgency, steatorrhea and increased defecation.

• Rare reports of liver injury in people taking orlistat.

• It interferes with the absorption of fat-soluble vitamins and B-carotene. Patients should be advised to take a multivitamin supplement that contains vitamins A, D, E, and K and also B-carotene (not within 2 hr. of orlistat).

• It interferes with absorption of other medications such as amiodarone and levothyroxin (should be separated by at least 4 hr.)

• Contraindicated in patients with chronic malabsorption syndrome or cholestasis.

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