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Isoniazid: Uses, Side effects, Dosage

Isoniazid is used in combination with other drugs to treat tuberculosis (TB; a serious infection that affects the lungs and typically other parts of the body). Isoniazid is additionally used with different medicine to treat individuals with latent (resting or nongrowing) TB as well as those in close contact with people that have active TB, a positive tuberculin skin test, human immunodeficiency virus (HIV), and people with pulmonary fibrosis (scarring of the lungs with an unknown cause). isoniazid is in a category of medicines known as antituberculosis agents. It works by killing the bacterium that causes TB.

  • Isoniazid is a prodrug and should be activated by bacterial catalase. Specifically, activation is related to the reduction of the mycobacterial ferric KatG catalase-peroxidase by hydrazine and reaction with oxygen to create an oxyferrous enzyme complex. Once activated, INH inhibits the synthesis of mycolic acids, an important part of the bacterial cell wall. At therapeutic levels, INH is bacteriocidal against actively growing intracellular and extracellular Mycobacterium tuberculosis organisms. Specifically, isoniazid inhibits InhA, the enoyl reductase from Mycobacterium tuberculosis, by forming a covalent adduct with the nad cofactor. it’s the INH-NAD adduct that acts as a slow, tight-binding competitive inhibitor of InhA.
  • There are 2 stages of the treatment for tuberculosis. within the initial two months treatment is geared toward killing as many bacterium as possible. Thus many anti-TBmedicinese with totally different mechanisms of action are used at the same time (usually rifampicin, pyrazinamide, isoniazid and ethambutol). after this point a number of the medicines are stopped and therefore the others (usually rifampicin and isoniazid) are continued for an additional four months to kill any remaining bacterium. isoniazid is employed in each stages of treatment.
  • Pregnancy: It can be used during pregnancy.(Not known to be harmful)

 

Isoniazid Dosage:

Adult Dose for Active TB  is 5 mg/kg (up to 300 mg) IM or orally once on a daily basis, or 15 mg/kg (up to 900 mg) 2 to 3 times every week. duration of therapy is typically 6 months or 3 months beyond culture conversion (when given with rifampin and pyrazinamide).

Adult Dose for prophylaxis of  TB is 300 mg orally per day in a single dose or 900 mg orally 2 to 3 times every week. isoniazid ought to be continued for 6 months to stop the development of active TB in patients with no complicating factors.

Isoniazid  Side Effects:

The following are some of the side effects that are known to be associated with this drug.

  • Dry mouth.
  • Constipation.
  • Difficulty urinating.
  • Inflammation of the liver (hepatitis).
  • Fever.
  • Dizziness or spinning sensation (vertigo).
  • Psychotic episodes, e.g (hallucinations).
  • Seizures (convulsions).
  • Raised blood sugar levels (hyperglycemia)
  • Blood disorders.
  • Skin reactions.Inflammation of the nerves (neuritis), which may cause pins and needles sensations, muscle weakness or blurred vision
  • Nausea and vomiting.
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