niacin

Required as coenzymes (for lipid metabolism, glycogenolysis, and tissue respiration).
Large doses decrease lipoprotein and triglyceride synthesis by inhibiting the release of free fatty acids from adipose tissue and decreasing hepatic lipoprotein synthesis.
Cause peripheral vasodilation in large doses.

Therapeutic effects:

Decreased blood lipids.
Supplementation in deficiency states.

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed following oral administration.

Distribution: Widely distributed following conversion to niacinamide.

Metabolism/Excretion: Amounts required for metabolic processes are converted to niacinamide. Large doses of niacin are excreted unchanged in the urine.

Half-Life: 45 min.

Time/Action Profile ⬆ ⬇

(effects on blood lipids)

ROUTE	ONSET	PEAK	DURATION
PO (cholesterol)	several days	unknown	unknown
PO (triglycerides)	several hr	unknown	unknown

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity to niacin;
Some products may contain tartrazine and should be avoided in patients with known hypersensitivity;
OB: Pregnancy (when used for treatment of hypercholesterolemia);
Lactation: Lactation.

Use Cautiously in:

Hepatic impairment;
Arterial bleeding;
Peptic ulcer disease;
Gout;
Glaucoma;
Diabetes mellitus;
OB: Use during pregnancy for the treatment of hypertriglyceridemia only if the potential maternal benefit justifies potential fetal risk;
Pedi: Safety and effectiveness not established in children.

Adv. Reactions/Side Effects ⬆ ⬇

Adverse reactions and side effects refer to doses used to treat hyperlipidemia

CV: orthostatic hypotension

Derm: flushing of the face and neck, pruritus, burning, dry skin, hyperpigmentation, ↑sebaceous gland activity, rash, stinging or tingling of skin

EENT: blurred vision, loss of central vision, proptosis, toxic amblyopia

Endo: hyperglycemia

GI: GI upset, bloating, diarrhea, dry mouth, flatulence, heartburn, HEPATOTOXICITY, hunger pains, nausea, peptic ulceration

GU: glycosuria

Metab: hyperuricemia

MS: myalgia

Neuro: dizziness, nervousness, panic

Interactions ⬆ ⬇

Drug-drug:

↑risk of myopathy with concurrent use of HMG-CoA reductase inhibitors.
Additive hypotension with antihypertensive agents.
Large doses may ↓ uricosuric effects of probenecid.

Route/Dosage ⬆ ⬇

PO (Adults ): Hyperlipidemia: Immediate-release: 250 mg once daily; ↑ dose every 4–7 days to desired response (usual dose = 1.5–2 g/day in 2–3 divided doses); after 2–3 mo, may ↑ at 2–4-wk intervals to 1 g 3 times daily; Extended-release: 500 mg at bedtime for 4 wk, then 1 g at bedtime for 4 wk; may then ↑ dose every 4 wk by 500 mg/day to maximum of 2 g/day. Dietary supplement: 50 mg twice daily or 100 mg once daily.

Availability ⬆ ⬇

(Generic available)

Tablets: 50 mg^OTC; 100 mg^OTC; 250 mg^OTC; 500 mg^{Rx, OTC}
Extended-release tablets: 500 mg^{Rx, OTC}; 750 mg^{Rx, OTC}; 1000 mg^{Rx, OTC}
Extended-release capsules: 250 mg^{Rx, OTC}; 500 mg^{Rx, OTC}

Assessment ⬆ ⬇

Vitamin Deficiency: Assess patient for signs of niacin deficiency (pellagra: dermatitis, stomatitis, glossitis, anemia, nausea and vomiting, confusion, memory loss, delirium) prior to and periodically during therapy.
Hyperlipidemia: Obtain a diet history, especially with regard to fat consumption.

Lab Test Considerations:

Monitor serum glucose and uric acid levels and hepatic function tests periodically during prolonged high-dose therapy. Notify health care professional if AST, ALT, or LDH becomes elevated. May ↑ prothrombin times and ↓ serum albumin.
- High-dose therapy may cause ↑ serum glucose and uric acid levels.
- When niacin is used as a lipid-lowering agent, monitor serum cholesterol and triglyceride levels prior to and periodically during therapy.

Implementation ⬆ ⬇

Because of infrequency of single B-vitamin deficiencies, combinations are commonly administered.
PO: Administer with meals or milk to minimize GI irritation.
- DNC: Extended-release tablets and capsules should be swallowed whole, without breaking, crushing, or chewing. Use calibrated measuring device to ensure accurate dose of solution.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take niacin as directed.
Inform patient that cutaneous flushing and a sensation of warmth, especially in the face, neck, and ears; itching or tingling; and headache may occur within the first 2 hr after taking the drug. These effects are usually transient and subside with continued therapy. If flushing is distressing or persistent, aspirin or an NSAID given 30 min before each dose or slow upward titration of dose may decrease flushing. Advise patient to avoid ingestion of alcohol or hot or spicy foods/liquids concurrently with niacin to minimize flushing.
- Advise patient to change positions slowly to minimize orthostatic hypotension.
- Instruct patients taking long-term OTC extended-release niacin to report signs of hepatotoxicity (darkening of urine, light-gray-colored stool, loss of appetite, severe stomach pain, yellow eyes or skin) to health care professional.
- Advise females of reproductive potential that doses used for hypercholesterolemia are higher than those for dietary supplementation. Discontinue niacin used for hypercholesterolemia during pregnancy and avoid breastfeeding during therapy.
- Emphasize the importance of follow-up examinations to evaluate progress.
Vitamin Deficiency: Encourage patient to comply with dietary recommendations of health care professional. Explain that the best source of vitamins is a well-balanced diet with foods from the four basic food groups.
- Foods high in niacin include meats, eggs, milk, and dairy products; little is lost during ordinary cooking.
- Patients self-medicating with vitamin supplements should be cautioned not to exceed RDA. The effectiveness of megadoses for treatment of various medical conditions is unproved and may cause side effects.
Hyperlipidemia: Advise patient that this medication should be used in conjunction with dietary restrictions (fat, cholesterol, carbohydrates, alcohol), exercise, and cessation of smoking.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

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