Liv.52, a polyherbal Ayurvedic formulation, exhibited hepatoprotective function when tested against chronic antitubercular drug treated rats. Suppression of GSH and antioxidant enzymes (superoxide dismutase, catalase, GPX and GST) were noticed in the liver of antitubercular drug treated animals, accompanied with an increased production of lipid peroxides. Liv.52 afforded hepatoprotection by inhibiting lipid peroxide production and, as a result, the animals showed improved antioxidant status.

Drug - induced hepatotoxicity is a potentially serious adverse effect of the currently used antitubercular chemotherapeutic regimens containing isoniazed (INH), rifampicin and pyrazinamide^1-3. Adverse effects of antitubercular therapy are sometimes potentiated by multiple drug regimen. Thus, though INH, rifampicin and pyrazinamide each in itself are potentially hepatotoxic, when given in combination their toxic effect is enhanced. The conversion of monoacetyl hydrazine, a metabolite of INH, to a toxic metabolite via cytochrome P₄₅₀ leads to hepatotoxicity. Patients on concurrent rifampicin therapy have an increased incident of hepatitis. This has been postulated to be due to rifampicin-induced cytochrome P₄₅₀ enzyme-induction, causing an increased production of toxic metabolites from acetyl hydrazine (AcHz)⁴. Other investigators demonstrated that rifampicin increases the metabolism of INH to isonicotinic acid and hydrazine, both of which are hepatotoxic⁵. The plasma half life of AcHz (metabolite of INH) is shortened by rifampicin and AcHz is quickly converted to its active metabolites by increasing the oxidative elimination rate of AcHz, which is related to the higher incidence of liver necrosis caused by INH and rifampicin in combination⁶. Rifampicin induction of the hydrolysis pathway of INH metabolism into the hepatotoxic metabolite hydrazine was reported by Askgaard et al.⁷ Pharmacokinetic interaction exists between rifampicin and pyrazinamide in tuberculotic patients, when these drugs are administered concomitantly. Pyrazinamide decreases blood levels of rifampicin by decreasing its bioavailability and increasing its clearance⁸. Pyrazinamide, in combination with INH and rifampicin, appears to be associated with an increased incidence of hepatotoxicity⁹.

The aim of the present work was to study the effect of Liv.52, an established hepatoprotective polyherbal formulation^10,11, on the hepatoxicity produced by the three antitubercular agents given together.

Liv.52 is an Ayurvedic formulation containing various herbomineral principles designed to combat liver injury and to protect liver against damage. It is available on the market in a tablet form, the composition of which is given in Table 1.

Drugs and chemicals – Isoniazid, rifampicin and pyrazinamide, bovine serum albumin and glutathione were obtained from Sigma, USA. Liv.52 was gifted by The Himalaya Drug Company, Bangalore, India.

Animals – Male Wistar rats (150 ± 10g) were maintained in standard environmental conditions. They were fed with commercial pelleted diet obtained from Hindustan Lever Ltd. and water ad libitum. Animals were housed six per cage at 27 ± 2ºC with constant 55% humidity, on a 12-h light/dark cycle.

Antihepatotoxic activity – Liv.52 was suspended in water and administered orally. Isoniazid and pyrazinamide were dissolved in sterile distilled water whereas rifampicin was first dissolved in 0.5ml of 0.1N HC1 and then made up to the required volume by adding sterile distilled water; all these drugs together were given orally by gastric incubation.

Animals were divided into 4 groups (n=6): Group I – control animals receiving no treatment; Group-II – animals receiving Liv.52 (500mg/kg, p. o.) for 2 weeks served as drug control; Group-III – animals receiving all the three antitubercular drugs for 2 weeks (isoniazid 7.5mg/kg, rifampicin 10mg/kg, pyrazinamide 35mg/kg, p.o.); Group IV-animals receiving simultaneous treatment of Liv.52 and all the three antitubercular drugs for 2 weeks.

At the end of the treatment, the animals were fasted 24 h and sacrificed by decapitation. The liver was dissected out, washed with chilled physiological saline, weighted, homogenized in 0.1M Tris HC1 buffer (pH 7.4) at 4ºC in potter Elvejem homogenizer, and then used for the evaluation: lipid peroxides (LPO)¹² and glutathione (GSH)¹³, along with the activities of superoxide dismutase (SOD)¹³, catalase (CAT)¹⁴, glutathione peroxidase (GPX)¹⁵ and glutathione S-transferase (GST)¹⁶ were assayed.

Animals treated with the combination of INH, rifampicin and pyrazinamide showed a significant increase in liver peroxide contents, and a significant decrease on SOD, CAT, GPX and GST activities. Also the glutathione level was significantly reduced. Treatment with Liv.52 (500mg/kg, p.o.) significantly modified the hepatotoxic effect of the antitubercular drugs. As shown in Table 2, Liv.52 afforded protection against lipid peroxidation, the above-mentioned parameters being almost restored to normal values.

Liv.52 affords protection against lipid peroxidation by increasing tocopherol level^17,18. The extracts of Cichorium intybus and Solanum nigrum (constitutents of Liv.52) have been reported to contain many polyphenolic compounds, mainly flavonoids. The antioxidant activity of the extract may therefore be due to the presence of polyphenolic constituents¹⁹.

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