Sibutramine is a centrally-acting serotonin-norepinephrine reuptake inhibitor structurally related to amphetamines, although its mechanism of action is distinct. Sibutramine is used in combination with a reduced calorie diet and exercise to help people who are overweight lose weight and maintain their weight loss. Sibutramine is in a class of medications called appetite suppressants. It works by acting on appetite control centers in the brain to decrease appetite. Sibutramine is a medication that assists with weight-loss by altering neurotransmitters within the brain. Neurotransmitters are chemicals that are produced and released by nerves in order to communicate with other nerves. Released neurotransmitters may attach to other nerves or they may be taken up again by the nerves that release them, a process termed reuptake. Sibutramine blocks the reuptake of the neurotransmitters dopamine, norepinephrine, and serotonin. Blocking the reuptake of neurotransmitters alters the balance of neurotransmitters within the nerve cells and thereby affect nerve function and interaction. Sibutramine is a diet aid. It appears to work by regulating chemicals in the brain that reduce hunger or craving for food. Sibutramine is a neurotransmitter reuptake inhibitor that reduces the reuptake of serotonin (by 53%), norepinephrine (by 54%), and dopamine (by 16%), thereby increasing the levels of these substances in synaptic clefts and helping enhance satiety; the serotonergic action, in particular, is thought to influence appetite. Older anorectic agents such as amphetamine and fenfluramine force the release of these neurotransmitters rather than affecting their reuptake.Despite having a mechanism of action similar to tricyclic antidepressants, sibutramine has failed to demonstrate antidepressant properties in animal studies. It was approved by the U.S. Food and Drug Administration (FDA) in November 1997 for the treatment of obesity.
Sibutramine effects
You will probably lose weight soon after you begin taking sibutramine and following your diet and exercise program. Be sure to monitor your weight, and call your doctor if you do not lose at least 4 pounds (1.8 kilograms) during your first 4 weeks of therapy. Your doctor may wish to change your dose of sibutramine. sibutramine may not work for everybody. Tell your doctor how much weight you lose during your treatment with sibutramine. Your doctor may tell you to stop taking sibutramine if you do not lose a certain amount of weight during the first 3 to 6 months of your treatment. You may not continue to lose weight after your first 6 months of treatment. However, you should continue to take sibutramine even if you have stopped losing weight. If you stop taking sibutramine, you may gain weight. Do not stop taking sibutramine without talking to your doctor.
Sibutramine hydrochloride monohydrate is an orally administered agent for the treatment of obesity. Chemically, the active ingredient is a racemic mixture of the (+) and (-) enantiomers of cyclobutanemethanamine, 1-(4-chlorophenyl)-N,N-dimethyl-α-(2-methylpropyl)-, hydrochloride, monohydrate, and has an empirical formula of C17H29Cl2NO. Its molecular weight is 334.33. Sibutramine hydrochloride monohydrate is a white to cream crystalline powder with a solubility of 2.9 mg/mL in pH 5.2 water. Its octanol: water partition coefficient is 30.9 at pH 5.0. Each Meridia / reductil capsule contains 5 mg, 10 mg, and 15 mg of sibutramine hydrochloride monohydrate. It also contains as inactive ingredients: lactose monohydrate, NF; microcrystalline cellulose, NF; colloidal silicon dioxide, NF; and magnesium stearate, NF in a hard-gelatin capsule [which contains titanium dioxide, USP; gelatin; FD&C Blue No. 2 (5- and 10-mg capsules only); D&C Yellow No. 10 (5- and 15-mg capsules only), and other inactive ingredients]. Sibutramine is well absorbed from the GI tract (77%), but undergoes considerable first-pass metabolism, reducing its bioavailability. The drug itself reaches its peak plasma level after 1 hour and has also a half-life of 1 hour. Sibutramine is metabolized by cytochrome P450 isozyme CYP3A4 into two pharmacologically-active primary and secondary amines (called active metabolites 1 and 2) with half-lives of 14 and 16 hours, respectively. Peak plasma concentrations of active metabolites 1 and 2 are reached after three to four hours. The following metabolic pathway mainly results in two inactive conjugated and hydroxylated metabolites (called metabolites 5 and 6). Metabolites 5 and 6 are mainly excreted in the urine.
Do NOT use Sibutramine if:
- you are allergic to any ingredient in Sibutramine
- you have an eating disorder (eg, anorexia, bulimia), uncontrolled or severe high blood pressure, or increased blood pressure in the lungs
- you have a history of heart or blood vessel problems (eg, chest pain, fast or irregular heartbeat, heart attack, heart failure, hardening of the arteries or blood vessels, poor circulation in the legs), or stroke or transient ischemic attack (TIA) (mini-stroke)
- you have severe liver or kidney problems or you are on dialysis for severe kidney problems
- you are taking a selective serotonin reuptake inhibitor (SSRI) (eg, fluoxetine), another appetite suppressant, or you have taken a monoamine oxidase inhibitor (MAOI) (eg, phenelzine) within the last 14 days
- you are over 65 years old
Contact your doctor or health care provider right away if any of these apply to you.
Sibutramine is contraindicated in patients with:
- Psychiatric conditions as bulimia nervosa, anorexia nervosa, serious depression or preexisting mania
- Patients with a history of or a predisposition to drug or alcohol abuse
- Hypersensitivity to the drug or any of the inactive ingredients
- Patients below 18 and above 65 years of age
- Concomitant treatment with a MAO inhibitor, antidepressant or other centrally active drugs, particularly other anoretics
- History of peripheral arterial disease
- Hypertension that is not sufficiently controlled (e.g., > 145/90 mmHg), caution in controlled hypertension
- Existing pulmonary hypertension
- Existing damage on heart valves, coronary heart disease, congestive heart failure, serious arrhythmias, previous myocardial infarction
- A history of coronary artery disease (e.g., angina, history of myocardial infarction), congestive heart failure, tachycardia, peripheral arterial occlusive disease, arrhythmia or cerebrovascular disease (stroke or transient ischemic attack (TIA))
- Stroke or transient ischemic attack (TIA)
- Hyperthyroidism (overactive thyroid gland)
- Closed angle glaucoma
- Seizure disorders
- Enlargement of the prostate gland with urinary retention (relative C.I.)
- Pheochromocytoma
- Pregnant and lactating women (relative C.I.)
Before using Sibutramine:
Some medical conditions may interact with Sibutramine. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:
- if you are pregnant, planning to become pregnant, or are breast-feeding
- if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
- if you have allergies to medicines, foods, or other substances
- if you have kidney or liver problems, heart problems, high blood pressure, bleeding problems, narrow-angle glaucoma, gallbladder problems (eg, gallstones), underactive thyroid, or seizures
- if you have a history of mental or mood problems (eg, depression), or suicidal thoughts or actions
- tell your doctor and pharmacist if you are allergic to sibutramine or any other medications.
- tell your doctor if you are taking monoamine oxidase (MAO) inhibitors, including isocarboxazid (Marplan), phenelzine (Nardil), selegiline (Eldepryl, Emsam, Zelapar), and tranylcypromine (Parnate), or have stopped taking them within the past 2 weeks. Your doctor may tell you not to take sibutramine. Do not start taking these drugs for at least 2 weeks after you stop taking sibutramine.
- tell your doctor if you are taking other prescription or nonprescription medications, herbal products or nutritional supplements to help you lose weight such as benzphetamine (Didrex), methamphetamine (Desoxyn), phendimetrazine (Adipost, Bontril, others), and phentermine (Adipex-P, Phentride, others). Your doctor may tell you not to take sibutramine.
- tell your doctor if you have or ever had an eating disorder such as anorexia nervosa (abnormal focus on being thin that causes you to eat very little and exercise excessively) or bulimia nervosa (eating large amounts of food and then removing the food from the body using diuretics (water pills), laxatives, or vomiting), angina (chest pain), congestive heart failure (heart is unable to pump blood well enough), a heart attack, high blood pressure, irregular heartbeat, peripheral arterial disease (PAD; narrowing of the blood vessels outside of your heart), or a stroke or ministroke. Your doctor will probably tell you not to take sibutramine.
- tell your doctor if you have or have ever had cancer; depression; gallstones (clumps of hardened material that can block the passages from the liver to intestine); glaucoma (an eye disease); hemophilia or other bleeding problems; migraine headaches; osteoporosis (thinning and weakening of the bones); Parkinson’s disease (a disorder of the nervous system that causes difficulties with movement, muscle control, and balance); seizures; pulmonary hypertension (high pressure in the vessel that moves blood from the heart to the lungs); or kidney, liver, or thyroid disease. Also tell your doctor if you have ever used street drugs or overused prescription medications.
- tell your doctor if you are pregnant or are breast-feeding. You should use effective birth control to be sure you do not become pregnant while you are taking sibutramine. Ask your doctor if you need help choosing a method of birth control.
- talk to your doctor about the risks and benefits of taking this medication if you are 65 years of age or older. Older adults should not usually take sibutramine.
- if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking sibutramine.
- you should know that sibutramine may make you drowsy and may affect your judgment, your ability to think, and your coordination. Do not drive a car or operate machinery until you know how this medication affects you.
remember that alcohol can add to the drowsiness caused by this medication. Ask your doctor about the safe use of alcoholic beverages while you are taking sibutramine.
- ask your doctor about drinking coffee, tea, or caffeinated beverages while taking sibutramine. Caffeine may make the side effects from sibutramine worse.
Side effects of Sibutramine
A higher number of cardiovascular events has been observed in people taking sibutramine versus control (11.4% vs. 10.0%).[14] In 2010 the FDA noted the concerns that sibutramine increases the risk of heart attacks and strokes in patients with a history of cardiovascular disease.
Frequently encountered side effects are: dry mouth, paradoxically increased appetite, nausea, strange taste in the mouth, upset stomach, constipation, trouble sleeping, dizziness, drowsiness, menstrual cramps/pain, headache, flushing, or joint/muscle pain.
Sibutramine can substantially increase blood pressure and pulse in some patients. Therefore regular monitoring needs to be performed.
The following side effects are infrequent but serious and require immediate medical attention: cardiac arrhythmias, paresthesia, mental/mood changes (e.g., excitement, restlessness, confusion, depression, rare thoughts of suicide).
Symptoms that require urgent medical attention are seizures, problems urinating, abnormal bruising or bleeding, melena, hematemesis, jaundice, fever and rigors, chest pain, hemiplegia, abnormal vision, dyspnea and edema.
Currently, no case of pulmonary hypertension has been noted, although related compounds (such as Fen-Phen) have shown this rare but clinically significant problem.
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat, Back pain; constipation; dizziness; dry mouth; flu-like symptoms; headache; increased or decreased appetite; joint pain; nausea; nervousness; painful menstruation; runny nose; sleeplessness; sore throat; upset stomach; weakness.
Stop using sibutramine and call your doctor at once if you have a serious side effect such as:
- flu symptoms;
- fast or pounding heartbeats;
- dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, chest pain, uneven heartbeats);
- new or worsening shortness of breath;
- seizure (convulsions)
Seek medical attention right away if any of these SEVERE side effects occur:
Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue; unusual hoarseness); agitation; anxiety; blurred vision or other vision changes; change in the amount of urine; chest, left arm, or jaw pain; clumsiness; confusion; difficulty breathing; disorientation; excitement; eye pain; fainting; fast or irregular heartbeat; high fever; increased sweating; large, unchanging pupils; loss of consciousness; mood or mental changes (eg, depression, mania, psychosis, thoughts of suicide or suicide attempt); numbness of an arm or leg; one-sided weakness; restlessness; seizures; severe or persistent dizziness, headache, or weakness; shivering; shortness of breath; stomach pain; swelling of the feet, ankles, or legs; tremors; unusual bruising or bleeding; vomiting.