DRUGS & SUPPLEMENTS
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Isonex is recommended for all forms of tuberculosis in which organisms are susceptible. However, active tuberculosis must be treated with multiple concomitant antituberculosis medications to prevent the emergence of drug resistance. Single-drug treatment of active tuberculosis with Isonex, or any other medication, is inadequate therapy.
Isonex is recommended as preventive therapy for the following groups, regardless of age. (Note: the criterion for a positive reaction to a skin test (in millimeters of induration) for each group is given in parenthesis):
Preventive therapy may be considered for HIV infected persons who are tuberculin-negative but belong to groups in which the prevalence of tuberculosis infection is high. Candidates for preventive therapy who have HIV infection should have a minimum of 12 months of therapy.
Additionally, in the absence of any of the above risk factors, persons under the age of 35 with a tuberculin skin test reaction of 10 mm or more are also appropriate candidates for preventive therapy if they are a member of any of the following high-incidence groups:
Children who are less than 4 years old are candidates for Isonex preventive therapy if they have >10 mm induration from a PPD Mantoux tuberculin skin test.
Finally, persons under the age of 35 who a) have none of the above risk factors (1-6); b) belong to none of the high-incidence groups; and c) have a tuberculin skin test reaction of 15 mm or more, are appropriate candidates for preventive therapy.
The risk of hepatitis must be weighed against the risk of tuberculosis in positive tuberculin reactors over the age of 35. However, the use of Isonex is recommended for those with the additional risk factors listed above (1-6) and on an individual basis in situations where there is likelihood of serious consequences to contacts who may become infected.
Isonex is contraindicated in patients who develop severe hypersensitivity reactions, including drug-induced hepatitis; previous isoniazid-associated hepatic injury; severe adverse reactions to Isonex such as drug fever, chills, arthritis; and acute liver disease of any etiology.
See the boxed WARNING .
All drugs should be stopped and an evaluation made at the first sign of a hypersensitivity reaction. If Isonex therapy must be reinstituted, the drug should be given only after symptoms have cleared. The drug should be restarted in very small and gradually increasing doses and should be withdrawn immediately if there is any indication of recurrent hypersensitivity reaction.
Use of Isonex should be carefully monitored in the following:
Because there is a higher frequency of Isonex associated hepatitis among certain patient groups, including Age > 35, daily users of alcohol, chronic liver disease, injection drug use and women belonging to minority groups, particularly in the post-partum period, transaminase measurements should be obtained prior to starting and monthly during preventative therapy, or more frequently as needed. If any of the values exceed three to five times the upper limit of normal, Isonex should be temporarily discontinued and consideration given to restarting therapy.
Isonex should not be administered with food. Studies have shown that the bioavailability of Isonex is reduced significantly when administered with food. Tyramine- and histamine-containing foods should be avoided in patients receiving Isonex. Because Isonex has some monoamine oxidase inhibiting activity, an interaction with tyramine-containing foods may occur. Diamine oxidase may also be inhibited, causing exaggerated response (e.g., headache, sweating, palpitations, flushing, hypotension) to foods containing histamine (e.g., skipjack, tuna, other tropical fish).
A report of severe acetaminophen toxicity was reported in a patient receiving Isonex. It is believed that the toxicity may have resulted from a previously unrecognized interaction between Isonex and acetaminophen and a molecular basis for this interaction has been proposed. However, current evidence suggests that Isonex does induce P-450IIE1, a mixed-function oxidase enzyme that appears to generate the toxic metabolites, in the liver. Furthermore it has been proposed that Isonex resulted in induction of P-450IIE1 in the patients liver which, in turn, resulted in a greater proportion of the ingested acetaminophen being converted to the toxic metabolites. Studies have demonstrated that pretreatment with Isonex potentiates acetaminophen hepatotoxicity in rats1,2.
Isonex is known to slow the metabolism of carbamazepine and increase its serum levels. Carbamazepine levels should be determined prior to concurrent administration with Isonex, signs and symptoms of carbamazepine toxicity should be monitored closely, and appropriate dosage adjustment of the anticonvulsant should be made3.
Potential interaction of ketoconazole and Isonex may exist. When ketoconazole is given in combination with Isonex and rifampin the AUC of ketoconazole is decreased by as much as 88% after 5 months of concurrent Isonex and rifampin therapy4.
Isonex may increase serum levels of phenytoin. To avoid phenytoin intoxication, appropriate adjustment of the anticonvulsant should be made5,6.
A recent study has shown that concomitant administration of Isonex and theophylline may cause elevated plasma levels of theophylline, and in some instances a slight decrease in the elimination of Isonex. Since the therapeutic range of theophylline is narrow, theophylline serum levels should be monitored closely, and appropriate dosage adjustments of theophylline should be made7.
A recent case study has shown a possible increase in the plasma level of valproate when co-administered with Isonex. Plasma valproate concentration should be monitored when Isonex and valproate are co-administered, and appropriate dosage adjustments of valproate should be made8.
Isonex has been shown to induce pulmonary tumors in a number of strains of mice. Isonex has not been shown to be carcinogenic in humans.. Isonex has been found to be weakly mutagenic in strains TA 100 and TA 1535 of Salmonella typhimurium (Ames assay) without metabolic activation.
Isonex has been shown to have an embryocidal effect in rats and rabbits when given orally during pregnancy. Isonex was not teratogenic in reproduction studies in mice, rats and rabbits. There are no adequate and well-controlled studies in pregnant women. Isonex should be used as a treatment for active tuberculosis during pregnancy because the benefit justifies the potential risk to the fetus. The benefit of preventive therapy also should be weighed against a possible risk to the fetus. Preventive therapy generally should be started after delivery to prevent putting the fetus at risk of exposure; the low levels of Isonex in breast milk do not threaten the neonate. Since Isonex is known to cross the placental barrier, neonates of Isonex treated mothers should be carefully observed for any evidence of adverse affects.
Since Isonex is known to cross the placental barrier, neonates of isoniazid-treated mothers should be carefully observed for any evidence of adverse effects.
The small concentrations of Isonex in breast milk do not produce toxicity in the nursing newborn; therefore, breast feeding should not be discouraged. However, because levels of Isonex are so low in breast milk, they can not be relied upon for prophylaxis or therapy of nursing infants.
The most frequent reactions are those affecting the nervous system and the liver.
Nervous System Reactions - Peripheral neuropathy is the most common toxic effect. It is dose-related, occurs most often in the malnourished and in those predisposed to neuritis (e.g., alcoholics and diabetics), and is usually preceded by paresthesias of the feet and hands. The incidence is higher in "slow inactivators".
Other neurotoxic effects, which are uncommon with conventional doses, are convulsions, toxic encephalopathy, optic neuritis and atrophy, memory impairment, and toxic psychosis.
Hepatic Reactions - See boxed WARNING. Elevated serum transaminase (SGOT; SGPT), bilirubinemia, bilirubinuria, jaundice, and occasionally severe and sometimes fatal hepatitis. The common prodromal symptoms of hepatitis are anorexia, nausea, vomiting, fatigue, malaise, and weakness. Mild hepatic dysfunction, evidenced by mild and transient elevation of serum transaminase levels occurs in 10% to 20% of patients taking Isonex. This abnormality usually appears in the first 1 to 3 months of treatment but can occur at any time during therapy. In most instances, enzyme levels return to normal, and generally, there is no necessity to discontinue medication during the period of mild serum transaminase elevation. In occasional instances, progressive liver damage occurs, with accompanying symptoms. If the SGOT value exceeds three to five times the upper limit of normal, discontinuation of the Isonex should be strongly considered. The frequency of progressive liver damage increases with age. It is rare in persons under 20, but occurs in up to 2.3 percent of those over 50 years of age.
Gastrointestinal Reactions - Nausea, vomiting, and epigastric distress.
Hematologic Reactions - Agranulocytosis; hemolytic, sideroblastic, or aplastic anemia, thrombocytopenia; and eosinophilia.
Hypersensitivity Reactions - Fever, skin eruptions (morbilliform, maculopapular, purpuric, or exfoliative), lymphadenopathy, and vasculitis.
Metabolic and Endocrine Reactions - Pyridoxine deficiency, pellagra, hyperglycemia, metabolic acidosis, and gynecomastia.
Miscellaneous Reactions - Rheumatic syndrome and systemic lupus erythematosus-like syndrome.
To report SUSPECTED ADVERSE REACTIONS, contact West-ward Pharmaceutical Corp. at 1-877-233-2001, and the FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
Isonex overdosage produces signs and symptoms within 30 minutes to 3 hours after ingestion. Nausea, vomiting, dizziness, slurring of speech, blurring of vision, and visual hallucinations are among the early manifestations. With marked overdosage, respiratory distress and CNS depression, progressing rapidly from stupor to profound coma, are to be expected, along with severe, intractable seizures. Severe metabolic acidosis, acetonuria, and hyperglycemia are typical laboratory findings.
Untreated or inadequately treated cases of gross Isonex overdosage, 80 mg/kg - 150 mg/kg, can cause neurotoxicity6 and terminate fatally, but good response has been reported in most patients brought under adequate treatment within the first few hours after drug ingestion.
Absorption of drugs from the GI tract may be decreased by giving activated charcoal. Gastric emptying should also be employed in the asymptomatic patient. Safeguard the patient"s airway when employing these procedures. Patients who acutely ingest > 80 mg/kg should be treated with intravenous pyridoxine on a gram per gram basis equal to the Isonex dose. If an unknown amount of Isonex is ingested, consider an initial dose of 5 grams of pyridoxine given over 30 to 60 minutes in adults, or 80 mg/kg of pyridoxine in children.
Ensure adequate ventilation, support cardiac output, and protect the airway while treating seizures and attempting to limit absorption. If the dose of Isonex is known, the patient should be treated initially with a slow intravenous bolus of pyridoxine, over 3 to 5 minutes, on a gram per gram basis, equal to the Isonex dose. If the quantity of Isonex ingestion is unknown, then consider an initial intravenous bolus of pyridoxine of 5 grams in the adult or 80 mg/kg in the child. If seizures continue, the dosage of pyridoxine may be repeated. It would be rare that more than 10 grams of pyridoxine would need to be given. The maximum safe dose for pyridoxine in Isonex intoxication is not known. If the patient does not respond to pyridoxine, diazepam may be administered. Phenytoin should be used cautiously, because Isonex interferes with the metabolism of phenytoin.
Obtain blood samples for immediate determination of gases, electrolytes, BUN, glucose, etc.; type and cross-match blood in preparation for possible hemodialysis.
Patients with this degree of INH intoxication are likely to have hypoventilation. The administration of sodium bicarbonate under these circumstances can cause exacerbation of hypercarbia. Ventilation must be monitored carefully, by measuring blood carbon dioxide levels, and supported mechanically, if there is respiratory insufficiency.
Both peritoneal and hemodialysis have been used in the management of Isonex overdosage. These procedures are probably not required if control of seizures and acidosis is achieved with pyridoxine, diazepam and bicarbonate.
Along with measures based on initial and repeated determination of blood gases and other laboratory tests as needed, utilize meticulous respiratory and other intensive care to protect against hypoxia, hypotension, aspiration, pneumonitis, etc.
: NOTE: For preventive therapy of tuberculous infection and treatment of tuberculosis, it is recommended that physicians be familiar with the following publications: (1) the recommendations of the Advisory Council for the Elimination of Tuberculosis, published in the MMWR: vol 42; RR-4, 1993 and (2) Treatment of Tuberculosis and Tuberculosis Infection in Adults and Children, American Journal of Respiratory and Critical Care Medicine: vol 149; 1359-1374, 1994.
For Treatment of Tuberculosis - Isonex is used in conjunction with other effective anti-tuberculosis agents. Drug susceptibility testing should be performed on the organisms initially isolated from all patients with newly diagnosed tuberculosis. If the bacilli become resistant, therapy must be changed to agents to which the bacilli are susceptible.
Usual Oral Dosage (depending on the regimen used):
15 mg/kg up to 900 mg day, two or three times/week
20-40 mg/kg up to 900 mg/day, two or three time/week
There are 3 regimen options for the initial treatment of tuberculosis in children and adults:
Option 1: Daily Isonex, rifampin, and pyrazinamide for 8 weeks followed by 16 weeks of Isonex and rifampin daily or 2-3 times weekly. Ethambutol or streptomycin should be added to the initial regimen until sensitivity to Isonex and rifampin is demonstrated. The addition of a fourth drug is optional if the relative prevalence of isoniazid-resistant Mycobacterium tuberculosis isolates in the community is less than or equal to four percent.
Option 2: Daily Isonex, rifampin, pyrazinamide, and streptomycin or ethambutol for 2 weeks followed by twice weekly administration of the same drugs for 6 weeks, subsequently twice weekly Isonex and rifampin for 16 weeks.
Option 3: Three times weekly with Isonex, rifampin, pyrazinamide, and ethambutol or streptomycin for 6 months.
*All regimens given twice weekly or 3 times weekly should be administered by directly observed therapy.
The above treatment guidelines apply only when the disease is caused by organisms that are susceptible to the standard antituberculous agents. Because of the impact of resistance to Isonex and rifampin on the response to therapy, it is essential that physicians initiating therapy for tuberculosis be familiar with the prevalence of drug resistance in their communities. It is suggested that ethambutol not be used in children whose visual acuity cannot be monitored.
The response of the immunologically impaired host to treatment may not be as satisfactory as that of a person with normal host responsiveness. For this reason, therapeutic decisions for the impaired host must be individualized. Since patients co-infected with HIV may have problems with malabsorption, screening of antimycobacterial drug levels, especially in patients with advanced HIV disease, may be necessary to prevent the emergence of MDRTB.
The basic principles that underlie the treatment of pulmonary tuberculosis also apply to Extra pulmonary forms of the disease. Although there have not been the same kinds of carefully conducted controlled trials of treatment of Extra pulmonary tuberculosis as for pulmonary disease, increasing clinical experience indicates that a 6 to 9 month short-course regimen is effective. Because of the insufficient data, miliary tuberculosis, bone/joint tuberculosis, and tuberculous meningitis in infants and children should receive 12 months therapy.
Bacteriologic evaluation of Extra pulmonary tuberculosis may be limited by the relative inaccessibility of the sites of disease. Thus, response to treatment often must be judged on the basis of clinical and radiographic findings.
The use of adjunctive therapies such as surgery and corticosteroids is more commonly required in Extra pulmonary tuberculosis than in pulmonary disease. Surgery may be necessary to obtain specimens for diagnosis and to treat such processes as constrictive pericarditis and spinal cord compression from Pott's Disease. Corticosteriods have been shown to be of benefit in preventing cardiac constriction from tuberculous pericarditis and in decreasing the neurologic sequelae of all stages of tuberculosis meningitis, especially when administered early in the course of the disease.
The options listed above must be adjusted for the pregnant patient. Streptomycin interferes with in utero development of the ear and may cause congenital deafness. Routine use of pyrazinamide is also not recommended in pregnancy because of inadequate teratogenicity data. The initial treatment regimen should consist of Isonex and rifampin. Ethambutol should be included unless primary Isonex resistance is unlikely.
Multiple-drug resistant tuberculosis (i.e., resistance to at least Isonex and rifampin) presents difficult treatment problems. Treatment must be individualized and based on susceptibility studies. In such cases, consultation with an expert in tuberculosis is recommended.
A major cause of drug-resistant tuberculosis is patient non-compliance with treatment. The use of DOT can help assure patient compliance with drug therapy. DOT is the observation of the patient by a health care provider or other responsible person as the patient ingests anti-tuberculosis medications. DOT can be achieved with daily, twice weekly or thrice weekly regimens, and is recommended for all patients.
Before Isonex preventive therapy is initiated, bacteriologically positive or radiographically progressive tuberculosis must be excluded. Appropriate evaluations should be performed if Extra pulmonary tuberculosis is suspected.
Adults over 30 Kg: 300 mg per day in a single dose.
Infants and Children: 10 mg/kg (up to 300 mg daily) in a single dose. In situations where adherence with daily preventative therapy cannot be assured, 20-30 mg/kg (not to exceed 900 mg) twice weekly under the direct observation of a health care worker at the time of administration8.
Continuous administration of Isonex for a sufficient period is an essential part of the regimen because relapse rates are higher if chemotherapy is stopped prematurely. In the treatment of tuberculosis, resistant organisms may multiply and the emergence of resistant organisms during the treatment may necessitate a change in the regimen.
For following patient compliance: the Potts-Cozart test9, a simple colorimetric6 method of checking for Isonex in the urine, is a useful tool for assuring patient compliance, which is essential for effective tuberculosis control. Additionally, Isonex test strips are also available to check patient compliance.
Concomitant administration of pyridoxine (B6) is recommended in the malnourished and in those predisposed to neuropathy (e.g., alcoholics and diabetics).
Isonex Tablets, USP 100 mg: White, Round Tablets; Debossed "West-ward" on one side and "260" on the Scored side.
Isonex Tablets, USP 300 mg: White, Round Tablets; Debossed "West-ward 261" on one side and Scored on the other side.
Store at 20-25°C (68-77°F). Protect from light and moisture.
Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure.
Adults and Children. Amer. J. Respir Crit Care Med.1994; 149: p 1359-1374.
Committee on Infectious Diseases; 23rd edition; p487.
West-ward Pharmaceutical Corp.
Eatontown, NJ 07724
Revised February 2011
Isonex 300mg Tablet
Depending on the reaction of the Isonex after taken, if you are feeling dizziness, drowsiness or any weakness as a reaction on your body, Then consider Isonex not safe to drive or operate heavy machine after consumption. Meaning that, do not drive or operate heavy duty machines after taking the capsule if the capsule has a strange reaction on your body like dizziness, drowsiness. As prescribed by a pharmacist, it is dangerous to take alcohol while taking medicines as it exposed patients to drowsiness and health risk. Please take note of such effect most especially when taking Primosa capsule. It's advisable to consult your doctor on time for a proper recommendation and medical consultations.Is Isonex addictive or habit forming?
Medicines are not designed with the mind of creating an addiction or abuse on the health of the users. Addictive Medicine is categorically called Controlled substances by the government. For instance, Schedule H or X in India and schedule II-V in the US are controlled substances.
Please consult the medicine instruction manual on how to use and ensure it is not a controlled substance.In conclusion, self medication is a killer to your health. Consult your doctor for a proper prescription, recommendation, and guidiance.
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The information was verified by Dr. Rachana Salvi, MD Pharmacology