Indian Journal of Experimental Biology Vol. 38, November 2000, pp. 1138-1142

Paracetamol and conventional antimalarial drugs induced hepatotoxicity and its protection by methionine in rats

ErvilJa E Dass* & K K Shah

Department of Pharmacology, Medical College, The Maharaja Sayajirao University of Baroda, Vadodara 390 001, India

Received 7 December 1998; revised 29 May 2000

Hepatotoxicity, induced in rats, by treatment with high doses of paracetamol and chloroquine was confirmed by estimating blood transaminase levels. Hepatoprotective effect was determined by administering combination of methionine (10% of paracetamol /chloroquine, p 0) and hepatotoxic drugs quinine. The results were confmned by histopathological examination of liver. Paracetamol (7g / kg) and chloroquine (970 mglkg) administration increased significantly the transaminase levels. Methionine alone did not produced any change. Hepatonecrosis induced by paracetamol, chloroquine alone and their combinations and its protection with methionine was revealed by histopathological study whereas the combination of paracetamol and methionine showed no significant histopathological difference when compared to the normal liver section. The results reveal that, methionine significantly prevented the rise in transaminases levels produced by hepatotoxic doses of paracetamol and chloroquine. But, to prevent occassional cases of paracetamol overdosage, it is not advisable to give methionine concurrently with paracetamol to patients who are taking paracetamol therapeutically.

Paracetamol is remarkably safe drug at therapeutic doses but is also the drug most commonly consumed by the patients in gross therapeutic overdosage; which may be responsible for the development of acute liver failure l

/ Considerable interest has been shown in the study of toxicity of paracetamol because of its clinical use as antipyretic as well as analgesic. In large do~es, paracetamol is known to produce hepatotoxicity both in experimental animals2 and also in human beings3

.

Conventional antimalarial drugs; like chloroquine4,

quinine5•6 and sulphadoxine-pyrimethamine . when

used alone or with chloroquine7•8 can induce

hepatotoxicity. Moreover, paracetamol due to its antipyretic property, is concurrently consumed at higher doses in case of chloroquine-resistant malaria.

Keeping above information in view the present study was designed with an aim to induce hepatotoxicity and demonstrate the hepatoprotective effects of methionine in rats.

Materials and Methods Young albino rats of either sex weighing 200- 400g

body weight were used. They were given free access to laboratory chow and tap water ad libitum. Animals

*Present address for correspondence : "Rebecca Nivas", Ground Floor, Opp. Madhuram Hospital, Fatehgunj, Baroda 390 002 India.

were allowed to acclimate in an environment of normal room temperature.

Rats were kept fasting 16 hours prior to administration of paracetamol. Paracetamol, as a freshly prepared suspension in distilled water was administered by intragastric cannula. The . volume administered was maintained constant at 20 rnI/kg, since Ferguson9 has shown that the drug toxicity can be increased with increasing volume of distilled water as vehicle. The rats were kept in a cage after administration of paracetamol and provided food and water ad libitum.

To study the hepatotoxicity induced by paracetamol,chloroquine, quinine and its protection by methionine the rats were divided into following experimental groups:

(1) Control group of 6 rats was taken to determine the normal liver function tests;

(2) paracetamol lO (7grnlkg) was administered as a single oral dose in a group of 9 rats;

(3) methionine ll per se (10% of paracetamol dose) was studied in a group of 6 rats;

(4) combination of paracetamol (7 g/kg) with methionine (10% of paracetamol dose) was given in group of 9 rats;

(5) chloroquine l2 (970 rnIkg) was administered as a single oral dose in a group of 6 rats;

(6) combination of paracetamol (7 g/kg) with chloroquine (970 mg/kg) was administered at the

DASS & SHAH: DRUGS-INDUCED HEPTOTOXICITY AND ITS PROTECTION 1139

above mentioned dose as a single oral dose in a group of 6 rats;

(7) combination of paracetamol (7g1kg,), chloroquine (970 mglkg) and methionine (10% of paracetamol dose) was given in a group of 6 rats;

(8) quininel3 (650 mglkg) was administered as a single oral dose for 2 days in group of 4 rats;

Following drugs administration, after 24 hr, the blood was collected and analysed for standard liver function tests (SGOT, SGPT) according to Reitman and Frankel method 14 by using autospan semiautomatic analyser. The livers were removed after blood collection, and prepared for histopathological examination in 10% formal · saline followed by dehydration, clearing and staining with Haematoxylene / Eosin stain.

Statistical analysis Results are expressed as means ± S.E. in terms of

international units litre-I. For comparison between two groups unpaired Student's t test was employed. P < 0.05 was considered significant.

Results and Discussion The results are presented in Table 1 and Figs 1-6. The evidence of hepatic necrosis from the liver

sections of paracetamol and chloroquine alone treated rats appears to be early damage indicated by hydropic vacuolation, marked congestion and necrosis of hepatocytes. Whereas liver sections from the combination of paracetamol and methionine and from paracetamol, chloroquine and methionine showed no significant difference as compared to normal liver sections.

Oral methionine given between 10 and 24 hours after ingestion of paracetamol seems more protective than iv N-acety1cysteine. The treatment protocol for oral methionine is simple and therapy is completed within 12 hr, as compared with 3 days for oral N­acety1cysteine treatment and 20 hr for iv N­acety1cysteinel5

• The side effects are unimportant and vomiting is mild when compared with that occurring after oral N-acety1cysteine treatment.

To be effective; methionine must be given within 8-10 hr of paracetamol ingestion. However some liver damage16 may still occur in highly susceptible patients of alcoholics poisoning in whom the treatment is delayed. Administration of methionine later than 10-12 hr after overdosage of paracetamol is not only useless but also dangerous, since it cannot be

metabolised by a damaged liver and may aggravate hepatotoxicity.

In the present study, methionine (700 mglkg i.e. 10% of paracet:p.mol dose) per se did not alter serum transarninases levels but decreases paracetamol induced rise in SGOT and SGPT levels significantly. The incorporation of 10% methionine with paracetamol is found to be optimal as reflected from the pilot experiments which were also carried out using 20% methionine per se which showed no significant difference between 10 and 20% of the corresponding paracetamol dose.

Concurrent adniinistration of paracetamol along with other hepatotoxic drugs is usually seen in many clinical situations17

• For example, paracetamol alone or in combination with chloroquine is found in malaria. It is a well known that malaria itself and chloroquine can also cause liver damage4

. Increased serum transaminases levels, due to choloNuine reflected the hepatic injury, which was further precipitated by paracetamol significantly. Methionine remarkably prevented the liver necrosis induced by

Table 1-Alteration of SGOT and SGPT levels by paracetamol, chloroquine and methionine and their combinations in rats

[Values are mean ± S.E. Figures in parentheses are number of animals]

Sr. Groups No.

SGOT (lUlL) SGPT (lUlL)

1 2 3 4

5

6 7

8

Control (6) Paracetamol (9) Methionine (6) Paracetamol

+ Methionine (10%) (9) Paracetamol

+ Methionine (20%) (9) Chloroquine (6) Chloroquine

+ Paracetamol (6) Chloroquine

+ Paracetamol

+ Methionine (6)

146.75 ± 16.12 910.44 + 53.5" 157.5 ±-11.4 b ·

185 ± 24.75<

179 ± 32.08 <

55.88 ± 8.01 207.55 + 24.75"

41.3 ±-3.47 b

51.8 ± 5.38<

40.7 ± 3.82<

415.0 ± 35.26" . 201.83 ± 9.66"

1974.67 ± 329.64 d 525.22 ± 126.99·

200 ± 26.26 t 69.17 ± 8.961

9 Quinine (4) 164.75 ± 17.91 b 47.50 ± 12.61 b

P values: 8< 0.001, as compared to control. bnot significant as compared to control. c< 0.001 , as compared to paracetamol alone. d<O.OOI , as compared to chloroquine alone. ·<0.05, as compared to chloroquine alone. f<O.OI as compared to chloroquine and paracetamol g<O.OOI as compared to chloroquine and paracetamol

\

1140 INDIAN J EXP BIOL, NOVEMBER 2000

Fig. 1 - Liver section from control rats, showing central vein (high power); Fig. 2(a) - Liver section from paracetamol treated rats . Marked congestion and necrosis detectable (low power); Fig. 2(b) - Liver section from paracetamol treated rats showing inflammatory reaction of central vein (high power); Fig. 3(a) - Liver section from paracetamo!.and methionine treated rats, cells apparently normal (low power); Fig. 3 (b) - Liver section from paracetamo! and methionine treated rats (high power)

DASS & SHAH: DRUGS-INDUCED HEPTOTOXICITY AND ITS PROTECTION 1141

Fig. 4-Liver section from chloroquine treated rats necrosis (low power); Fig. 5 - Liver section from chloroquine and paracetamol treated rats, severe necrosis (high power); Fig. 6-Liver section from chloroquine, paracetamol and methionine treated rats, central vein seen (high power)

combination of hepatotoxic doses of chloroquine and paracetamol which is reflected by non significant rise in transaminases levels. Another antimalarial drug. quinine. which is reported to cause hepatic damage as hypersensitivity reaction at the dose of 650 mg/kg. po did not cause any alteration in serum enzyme levels in the present study. The main events of histological changes reported from paracetamol (7 g/kg po). chloroquine (970 mg/kg po) per se and their combinations were hydropic vacuolation. marked congestion and necrosis of hepatocytes as seen by Boyd. et aZ IO

• Whereas those treated with paracetamol and methionine (700 mg/kg po). and paracetamol. chloroquine and methionine revealed apparently normal liver histology. This implies that concomitant administration of methionine prevented the hepatonecrotic changes in liver induced by . toxic doses of paracetamol and chloroquine.

In pilot experiments. no hepatotoxicity was observed even with 3.5 g/kg dose of paracetamol; which is around 120 times higher than the therapeutic dose for human beings. These findings cannot be extrapolated in clinical situations. The incidence of hepatotoxicity with paracetamol is very low in Indian population. So. to prevent occasional cases of paracetamol overdosage. it is not advisable to give methionine concurrently with paracetamol to patients who are taking paracetamol therapeutically.

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