The active ingredient can be administered orally or parenterally and the medicines containing it can be dispensed in pharmacies upon presentation of a repeatable medical prescription (RR). However, since they are classified as Tier A drugs, their cost can be reimbursed by the National Health System (NHS).
Examples of Medicines containing Isoniazid
- Nicozid®
- Rifater® (in combination with rifampicin and pyrazinamide)
- Rifinah® (in combination with rifampicin)
Note: even if isoniazid is used in combination therapy, this article will discuss warnings, precautions, interactions, side effects, use in pregnancy and lactation and contraindications of isoniazid alone and not of isoniazid administered in combination with other ingredients. active.
for the treatment of convulsions and epilepsy, since isoniazid increases their concentration in the blood causing a state of toxicity characterized by nystagmus, ataxia and lethargy. If the doctor deems it necessary to combine these two drugs, he will have to prescribe lower doses of phenytoin;Furthermore, patients who have to take isoniazid must undergo regular vision checks both before and during treatment, as the active ingredient in question can alter it.
It is also necessary to have regular liver function checks during treatment with isoniazid, especially if you are over 35 years of age. The risk of developing toxic effects on the liver increases when isoniazid is taken in combination with rifampicin or other drugs capable of increasing its blood concentration. The combination with rifampicin, moreover, can also increase the severity of any undesirable effects borne by the blood.
In addition to what has been said so far, it is important to know that peripheral neuritis could also occur during treatment with the active ingredient; in such cases, the doctor will prescribe vitamin B6 therapy.
Finally, it should be noted that treatment with isoniazid must be stopped immediately and the doctor immediately contacted if:
- Temporary and mild impairment of liver function (increased liver transaminases);
- Severe hepatitis (the risk of developing this inflammation is greater in elderly patients and in patients who consume alcoholic beverages daily);
- Nausea and / or vomiting;
- Loss of appetite
- Malaise;
- Allergic reactions.
Please note
In very early childhood, isoniazid should only be administered if the doctor deems it absolutely necessary and in any case under his direct control.
, as the association of these active ingredients can cause coordination disturbances and psychic disturbances.Also, before starting treatment with isoniazid, you should tell your doctor if you are taking other medications such as:
- Phenytoin, since isoniazid increases its concentration in the blood causing toxicity (see chapter "Warnings and Precautions");
- Aluminum hydroxide (active ingredient with antacid action), since it reduces the effects of isoniazid. If it is necessary to take it, isoniazid must be taken one hour before the antacid in question;
- Cycloserine, as if taken during treatment with isoniazid there could be an increase in side effects affecting the brain.
In any case, before starting to take isoniazid it is advisable to inform your doctor if you are taking, if you have recently taken or intend to take any kind of medicines or products, including non-prescription drugs. (SOP), over-the-counter (OTC) medicines, herbal and phytotherapeutic products, homeopathic products, etc.
Isoniazid and alcohol
Alcohol consumption should be avoided during treatment with isoniazid due to the increased risk of developing hepatitis and neuropathies.
, manifesting undesirable effects different in type and intensity, or not manifesting them at all.Among the undesirable effects that can occur during therapy with isoniazid, the frequency of which is not known, however, we find:
- Inflammation of the nerves preceded by tingling, numbness, sensitivity to contact, weakness in the arms and legs (peripheral neuropathies preceded by paresthetic disorders in the extremities). Similar side effects are especially common in patients who are malnourished, in patients who consume large amounts of alcohol (alcoholics) or have diabetes.
- Optic neuritis and optic atrophy;
- Convulsions;
- Hyperactivity;
- Euphoria;
- Insomnia;
- Toxic psychosis with mania and delusions;
- Nausea, vomiting, increased hepatic transaminases, hyperbilirubinemia and bilirubinuria;
- Hemolytic anemia, aplastic anemia, agranulocytosis, thrombocytopenia, eosinophilia;
- Hyperglycemia;
- Acidosis;
- Onset of symptoms caused by vitamin B6 and PP deficiency;
- Fever;
- Morbilliform, maculo-papular or exfoliative rashes;
- Lymphadenitis;
- Vasculitis;
- Rheumatoid syndrome;
- Lupus erythematosus-like syndrome;
- In case of intramuscular administration, irritation at the injection site.
Note: remember that these side effects concern the intake of isoniazid alone; for information on the side effects given by the association of isoniazid with other active ingredients, carefully read the package leaflet of the medicines to be taken.
Isoniazid overdose
Following excessive doses of isoniazid, symptoms such as:
- Nausea;
- He retched;
- Dizziness;
- Vision problems
- Speech disturbances.
In severe cases, the following can also occur:
- Convulsions;
- Respiratory depression;
- Alteration of the state of consciousness with rapid transition from stupor to coma;
- Increased acidity of the blood (metabolic acidosis);
- Acetonuria;
- Hyperglycemia.
Therefore, in the event of an isoniazid overdose - whether it is known or suspected - it is absolutely necessary to contact your doctor immediately or go to the nearest hospital, taking care to take the package of the medicine taken with you. Treatment is symptomatic and supportive.
, the microorganism responsible for tuberculosis.In detail, isoniazid acts on cells in the growth phase and is active on both intracellular and extracellular mycobacteria.
of the patient. In any case, the doses usually used will be reported below.
- Daily treatment: the recommended dose is 5-10 mg of isoniazid per kg of body weight per day, divided into 1-2 administrations in the initial phase of treatment, to be administered - depending on the case - orally, by injection into muscle (via intramuscular) or into a vein (intravenously).
- Intermittent treatment: the recommended dose is 10 mg of isoniazid per kg of body weight per day. Your doctor may adjust the dose according to the interval between doses and other medicines used together with the same isoniazid. If the medicine is to be given by injection into the spine (intrathecal), the recommended dose is 25-50 mg per day. day; if the medicine is to be given by injection into the lungs (instillations into the pleural cavity), the recommended dose is 50-250 mg per day.
Use in children
In children, the recommended dose is 6-10-20 mg of isoniazid per kg of body weight per day up to a maximum of 500 mg per day in older children. In particular, if the medicine is to be administered intrathecally, the recommended dose is 10-20 mg per day.
Use in patients with kidney problems or on hemodialysis
If you suffer from renal insufficiency, it is usually not necessary to reduce the dose.
If you have severe kidney problems (glomerular filtration less than 10ml / min), your doctor should reduce the dose of isoniazid to be given (66-75% of the normal dose).
If you are undergoing mechanical filtration of your blood (hemodialysis, peritoneal dialysis), your doctor will need to prescribe an additional dose of isoniazid.
Use in patients with liver problems
In patients with hepatic insufficiency, the doctor will need to reduce the dose of isoniazid administered to avoid the toxic effects of the active substance on the liver.
they must inform their doctor of their condition before starting to take isoniazid. Treatment with the active ingredient in this category of patients should only be carried out when clearly needed and under close medical supervision.
