Isoniazid tablets

Contamination of isoniazid tablets with diethylstilbestrol was the cause of several cases of precocious puberty in a children s tuberculosis ward (50). 

First-line drugs Isoniazid Tablets (50 mg 100 mg 300 m elixir (50 mgt5 Adults (max) 5 mg/kg (300 mg)... 

Vitamin deficiency can result from treatment with certain drags. Thus, destruction of intestinal microorganisms by antibiotic therapy can produce symptoms of vitamin K deficiency. Isoniazid, used to treat tuberculosis, is a competitive inhibitor of pyridoxal kinase, which is needed to produce pyridoxal phosphate. Isoniazid can produce symptoms of pyridoxine deficiency. To prevent this, pyridoxine is often incorporated into isoniazid tablets. Methotrexate and related folate antagonists act by competitively inhibiting dihydrofolate reductase (Chapter 27). 

Periodate Isoniazide (tablets) lincomycin hydrochloride (injections)... 

A microdialysis sampling has been used for multivessel dissolution testing of isoniazide tablets. The dialyzer is produced using regenerated hollow cellulose dialysis fibers, and the detection is at 254 nm. 

Sastry et al. used iodine and isonicotinic acid hydrazide for the spectrophotometric determination of diloxanide furoate in tablets and in syrups [30]. Powdered tablets or syrup were dissolved in methanol and hydrolyzed under reflux with dilute hydrochloric acid. The mixture was cooled, and excess HCI removed under vacuum. The hydrolysate was dissolved in and diluted with water. Iodine solution and the isoniazid solution were added at two minute intervals to a potassium h) drogen phthalate/HCl buffer solution (pH 3), and diluted with water. The solution was set aside for 10 minutes, whereupon the absorbance was measured at 630 nm against a reagent blank. 

Didanosine (ddl) NRTT1 Tablets, 400 mg daily,3 adjusted for weight. 30 min before or 2 h after meals. Separate dosing from fluoroquinolones and tetracyclines by 2 h Peripheral neuropathy, pancreatitis, diarrhea, nausea, hyperuricemia. Possible increase in myocardial infarction Avoid concurrent neuropathic drugs (eg, stavudine, zalcitabine, isoniazid), ribavirin, and alcohol. Do not administer with tenofovir... 

Oral contraceptive tablets are used to prevent pregnancy. Isoniazid may be used to prevent the development of active tuberculosis in those individuals who have been exposed to the disease but show no evidence of infection, in those who test positively for it but have no apparent disease, and in those with once active but now inactive disease. 

Barrosa (133) has reported the analysis of a mixture of pyridoxine and isoniazid in tablet formulation. Pyridoxine is determined by differential spectrophotometry at 324 nm. 

The addition of pyridoxine to usual doses of isoniazid of 5 mg/kg/day in adults and 8-10 mg/kg/day in children markedly reduces neurotoxicity (9). Adherence to therapy is improved by prescribing combined tablets containing 20 mg of pyridoxine per 100 mg of isoniazid. In otherwise healthy people, prescription of pyridoxine is not mandatory. However, it should be routinely given to malnourished patients and those predisposed to neuropathy (for example pregnant women, elderly people, and people with diabetes, alcoholism, or uremia) (7). 

Pyridoxine is used to prevent the adverse nervous system effects of isoniazid (1). Adherence to therapy is improved by prescribing combined tablets containing 20 mg of pyridoxine per 100 mg of isoniazid. 

Isoniazid is usually ingested orally as a tablet, capsule, or liquid. An injectable formulation is also available. 

Weigh 20 tablets and reduce to a fine powder. Weigh into a 400 mL beaker a weight of powder capable of yielding about 400 mg of isoniazide. Record the weight to the nearest 0.0001 g. Add 150 mL of distilled water and stir until the sample is dissolved to the best possible extent. Dilute to about 200 mL and filter on a 40 Whatman paper or equivalent. Catch the filtrate in a 250 mL volumetric flask, and wash with distilled water until the volume is close to the mark. Dilute to the mark and mix well. 

Figure 29 Biamperometric titration determination of isoniazide in tablets.

THERAPEUTIC USES Ethambutol (myambutol) has been used with notable success in the therapy of tuberculosis when given concurrently with isoniazid and largely has replaced aminosalicylic acid. Ethambutol is available for oral administration in tablets. The usual adult dose is 15 mg/kg given once a day. Some clinicians use 25 mg/kg/day for the first 60 days, followed by 15 mg/kg/day, particularly for those treated previously. Dose adjustment is necessary in patients with impaired renal function. Ethambutol is not recommended for children under 5 years of age because of concern about the ability to test their visual acuity. Children from ages 6-12 years should receive 10-15 mg/kg/day. 

The absorption of isoniazid from the gut is modestly reduced by aluminium hydroxide, less so by magaldrate, and not by affected by aluminium/magnesium hydroxide tablets or didanosine chew-able tablets. 

Didanosine chewable tablets contain antacids (aluminium/magnesium hydroxide) in the formulation, but it has been shown that they do not affect the bioavailability of isoniazid. ... 

Information on this interaction is limited, and it is not established. The clinical importance of the modest reductions in isoniazid levels with aluminium hydroxide in one study is uncertain, but likely to be small. However, aluminium/magnesium hydroxide did not interact, and neither did didanosine chewable tablets. 

Gallicano K, Sahai J, Zaror-Behrens G, Pakuts A. Effect of antacids in didanosine tablet on bioavailability of isoniazid. Antimicrob Agents Chemother (1994) 38, 894-7. 

In Ippen s (1978) case of contact eczema, the epicutaneous test, with isoniazid as substance or as pulverized tablets (from several manufacturers), showed in all instances definite eczema reactions which exceeded the test areas and required local treatment with corticosteroids. Wang and Schmeo (1974) report the case of a patient with occupational allergy to isoniazid. Beside the allergic reaction of the immediate type (asthma bronchiale) there was a latent sensitization of the delayed reaction type (eczema reaction). This latent sensitization was manifested in a circumscribed area by the epicutaneous test. Reexposure to the allergen led to an asthmatic spasm of the bronchi and to recrudescence of the eczematous cutaneous efflorescences when it was inhaled. 

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