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Probucol and Nicotinamides

Probucol

Butylated hydroxytoluene, not commonly used. It is used only in individuals who do not respond to other drugs.

  • Decrease cholesterol by about 10-15%
  • Decrease LDL by 10%
  • Decrease LDL by increasing their catabolism.

Absorption

Only 10% of drug is absorbed from intestines, rest is eliminated.

Effect is achieved in about 1-3 months.

Deposition

Slowly deposited in adipose tissues

Contraindications

Individuals having cardiovascular diseases as prolong QT interval.

Uses

Very less common uses.

Nicotinamides

  • Used in very high doses to produce antihyperlipidemic effects. Slow release preparations are available.
  • Decrease TGs by about 20-80%
  • Decrease LDL by 10%, but when given in combination with other hypolipidemic drugs, decrease in LDL is about 40-60%.
  • Increase HDL levels

Peak effect

Achieved in 1-4 days.

Mechanism of Action

Exact mechanism of action is not established. It is said that:

  • In liver- decrease production of cholesterol, VLDL and LDL.
  • In adipose tissues –inhibit lipolysis, so decrease fatty acids.
  • In plasma –stimulate the activity of lipases and increase clearance of lipoproteins (VLDL)
  • Increase levels of HDL by decreasing their catabolism
  • Increase Apo A-1, major lipoprotein in HDL.

Influence coagulation pathways, decrease fibrinogen  & increase tissue plasminogen activators

B3 acts like vitamin only when activated to NAD.

Oral nicotinamide has vitamin effects only and no anti-hyerlipidemic effects

Uses

  1. Hypercholesterolemia (Heterozygous familial hypercholesterolemia)- combination of resins and statins
  2. Hypertriglyceridemia
  3. Combined hyperlipidemia
  4. Severe mixed lipidemia
  5. Decreased HDL
  6. Increased lipoprotein A

Dose

1-2 g twice or thrice daily. Sustained release preparations are available.

Toxicity/Adverse Effects

  • GIT – Abdominal discomfort, pain, nausea, vomiting, diarrhea –remedy is to decrease dose, gastric acid inhibitors or antacids not containing aluminium
  • on prolonged use hyperglycemias (carbohydrate intolerance), hyperuricemias, precipitate gout and produce liver damage
  • Hyperpigmentation of skin and acanthosis nigricans (brownish black scaly lesions)
  • Eyes -Blurring of vision and amblyopia (one eye not functioning properly/lazy eye)
  • Can produce vasodilatation leading to cutaneous flushing and postural hypotension esp. if taking antihypertensives (PG mediated), tachyphylaxis when dose increased or used for longer periods
  • Can produce atrial arrhythmias
  • Postural hypotension
  • Birth defects in high doses
  • Pruritis
  • Liver enzyme deranged (increased ALT, acute necrosis, fulminant hepatic failure -rare

Contraindications

1. Pregnancy

2. When patient is taking antihypertensives

3. Gout

4. DM type II

5. Hepatic failure

Nicfuranose

Better tolerated than Nicotinic acid.  

Acipimox is derivative of Nicotinic acid, given in low doses. It has less toxicity, but potency is also low.

Niaspan has no hepatotoxicity.

Combinations

1. Resins and statins for type IIa hypercholesterolemia

2. Resins and fibrates for type II b hypercholesterolemia

3. Niacin and statins for type IIb hypercholesterolemia

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