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Obestat (Sibutramine hydrochloride monohydrate) Pharmacology

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Sibutramine hydrochloride monohydrate (Trade name: Obestat or Reductil) is an anorexiant that is used for the treatment of obesity.

This drug belongs to a class of drugs known as anorexiants, together with fenfluramine, and mazindol.  It also aids in both weight loss and the maintenance of weight loss. The drug is recommended for use with a reduced-calorie diet.

Sibutramine acts on the central nervous system (CNS) to suppress appetite (a true anorectic effect).

Sibutramine, originally intended as an antidepressant, has shown promise in the treatment of obesity. The drug inhibits the reuptake of serotonin and noradrenaline at the hypothalamic sites that regulate food intake.

Its main effects are to reduce food intake and cause dose-dependent weight loss, the weight loss is associated with a decrease in obesity-related risk factors. Sibutramine enhances satiety and is reported to produce a reduction in waist circumference (i.e. a reduction in visceral fat), a decrease in plasma triglycerides and very-low-density lipoproteins, but an increase in high-density lipoproteins.

In addition, beneficial effects on hyperinsulinemia and the rate of glucose metabolism are said to occur. There is some evidence that weight loss is associated with higher energy expenditure, possibly through an increase in thermogenesis mediated by the sympathetic nervous system.

A recent meta-analysis of three long-term treatment studies utilizing sibutramine in comparison with placebo (Padwal et al., 2003) concluded that there was a 4.6% loss of weight after 1 year's treatment with the drug. There was also a higher (15%) increase in patients who lost more than 10% of their body mass among those taking the drug.

Pharmacokinetic aspects

Sibutramine is given orally, is well absorbed and undergoes extensive first-pass metabolism. The metabolites are responsible for the pharmacological actions.

Steady-state blood levels of the metabolites occur within 4 days. The active metabolites are inactivated in the liver, and 85% of the inactive residues are excreted in the urine and feces.

Dosage

Adult dosage for treating obesity starts at 10 mg orally once a day though sometimes the dosage may be titrated to 15 mg/day after 1 month for those whom a lower dose is not effective or who are resistant.

The maximum dose is 15 mg/day.

Sometimes patients who cannot tolerate a dose of 10mg may take only 5mg, and those who are resistant to weight loss may take 15mg.

This drug is not approved in children younger than 16 years of age

It is indicated in patients with a body mass index greater than 30 kg/m2 or BMI greater than 27 kg/m2 who are at risk of cardiovascular disease or diabetes.

This drug is classified in Schedule IV of the Controlled Substances Act.

Side effects of Sibutramine

Sibutramine increases heart rate and blood pressure. Regular monitoring of these parameters is essential, and the drug is contraindicated if cardiovascular disease is present or if the systolic or diastolic pressure is raised by 10 mmHg or more.

Unwanted effects or side effects of Obestat include dry mouth, constipation, and insomnia.

Other rarer side effects, found in very few people, including

  • Seizures disorders
  • Bronchitis and nasal congestion,
  • Arthritis
  • Fever
  • Diarrhea
  • Dental problems,
  • Increased or decreased libido,
  • Difficulty breathing, itchy skin, and menstrual irregularities.
  • Agitation,
  • Inflammation of the stomach (gastritis)
  • Leg cramps,
  • Flatulence,
  • Hair loss,
  • Mental disorders such as depression, suicidal thoughts, and confusion.

Precautions

For individuals who have allergies to Sibutramine, they may experience hives, difficulty breathing, or swelling of the face, lips tongue or throat.

Obestat is known to raise blood pressure in some individuals, therefore, it is recommended that you monitor blood pressure and pulse rates regularly to detect any changes.

Chronic overuse can lead to marked tolerance and psychic dependence; caution with prolonged use

Do not use if uncontrolled hypertension, heart disease, or severe renal impairment or end-stage renal disease.

Take caution using Selective Serotonin Reuptake Inhibitors or other antidepressants, sumatriptan, ergotamine, and other serotonin agents to avoid the development of serotonin syndrome.

Obestat is contraindicated for use during or within 14 days of MAOIs due to a risk of a hypertensive crisis.

It should not be given to patients who have a serious eating disorder and also not recommended for people who are already taking some other kind of medication for weight loss.

If a patient has a history of drug abuse, he/she should be monitored for signs of misuse of Obestatn, such as the development of tolerance or increasing doses.

Drug interactions

Interactions with drugs that are metabolized by one of the P450 isoenzymes can occur.

Other medications that may affect the way Obestat works include medicines for coughs, colds, migraines depression, or pain, or medications that contain narcotics, lithium, tryptophan, or antibiotics.

Use in pregnancy and lactation period

Obestat is in Pregnancy Category C, which means it has not been determined to be safe for pregnant women or their babies. It has been shown to produce abnormalities in animal studies but has not been tested on human subjects.

It is not recommended that you take Obestat if you are pregnant or planning to become pregnant, and if you could become pregnant, you should employ reliable birth control.

It is not known whether Obestat is passed into breast milk; therefore it is not recommended for nursing mothers.

Use in children

Obestat has not been adequately tested for use in children, but it is expected that psychiatric side effects could be increased in this age group. For this reason, Obestat is not recommended for pediatric use.

Availability

Obestat available : 5mg capsules, 10mg capsules, 15mg capsules.


Post References

  • Science direct, textbook of clinical pharmacology

  • Revised on: 2021-06-24 09:33:43