Evaluation of anti-inflammatory activity, effect on blood pressure & gastric tolerability of antidepressants.

Background & objectives: Antidepressants are being used as analgesics for various pain related disorders like neuropathic and non neuropathic pain. Although their analgesic activity is well recognized but anti-inflammatory potential of antidepressants is still inconclusive. Since the antidepressants are used for longer duration, it becomes important to elucidate effect of anti-depressants on blood pressure and gastric mucosa. This study was undertaken to evaluate the anti-inflammatory potential of various antidepressant drugs as well as their effect on blood pressure and gastric tolerability on chronic administration in rats. Methods: Rat paw oedema model was used for studying anti-inflammatory activity, single dose of test drug (venlafaxine 20 and 40 mg/kg, amitryptline 25 mg/kg, fluoxetine 20 mg/kg) was administered intraperitoneally 45 min prior to administration of 0.1 ml of 1 per cent carrageenan in sub-planter region. Oedema induced in test group was compared with normal saline treated control group. For studying effect on blood pressure and gastric tolerability, test drugs were administered for 14 days. Blood pressure was recorded on days 0, 7 and 14 using tail cuff method. On day 14, 4 h after drug administration, rats were sacrificed and stomach mucosa was examined for ulcerations. Results: Pretreatment of rats with venlafaxine (40 mg/kg) resulted in a significant decrease in paw oedema as compared to control (2.4 ± 0.15 to 1.1 ± 0.16 ml, P<0.01). Similarly, in the group pretreated with fluoxetine, significant decrease in paw oedema was observed in comparison to control (P<0.05). Significant change in mean blood pressure was seen in rats pretreated with venlafaxine 40 mg/kg (126.7 ± 4.2 to 155.2 ± 9.7, P<0.05) and fluoxetine (143.5 ± 2.6 to 158.3 ± 1.2, P<0.05) on day 7. No significant difference with regard to gastric tolerability was observed among groups. Interpretation & conclusions: Our findings showed significant anti-inflammatory activity of venlafaxine (40 mg/kg) and fluoxetine but these drugs were also associated with an increase in blood pressure. No significant change in mean ulcer index was observed among groups.

Aliskiren: a novel renin inhibitor for hypertension.

Hypertension is one of the major causes of cardiovascular morbidity. Most patients who are on treatment for hypertension fail to achieve adequate control with the existing therapy and rates of cardiovascular morbidity remain high. As the renin-angiotensin-aldosterone system is strongly implicated in the development of hypertension-related target organ damage, intensive efforts have been devoted towards the development of drugs targeting this system. In addition to angiotensin converting enzyme inhibitors and angiotensin receptor blockers, inhibition of renin has also become a clinical reality. Aliskiren, a novel renin inhibitor, has overcome a number of shortcomings of existing drugs and is now available to address angiotensin production directly at its rate-limiting step.

Hepatoprotective effect of tocopherol against isoniazid and rifampicin induced hepatotoxicity in albino rabbits.

Antitubercular drug induced hepatotoxicity is a major hurdle for an effective treatment of tuberculosis. The present study was undertaken to assess the hepatoprotective potential of tocopherol (50 mg/kg and 100 mg/kg, ip) and to compare it with cimetidine (120 mg/kg, ip). Hepatotoxicity was produced by giving isoniazid (INH, 50 mg/kg, po) and rifampicin (RMP, 100 mg/kg, po) combination to albino rabbits for 7 days. Assessment of liver injury was done by estimating levels of alanine transaminase (ALT) and argininosuccinic acid lyase (ASAL) in serum and by histopathological examination of liver. Results revealed that pretreatment with high dose of tocopherol (100 mg/kg) prevented both biochemical as well as histopathological evidence of hepatic damage induced by INH and RMP combination. Moreover, tocopherol (100 mg/kg) was found to be a more effective hepatoprotective agent as compared to cimetidine.

Cytochrome P450 enzyme isoforms and their therapeutic implications: an update.

Clinicians should be cognizant of potential drug drug interactions and become familiar with the substrates, inhibitors and inducers of the common enzymatic pathways responsible for drug metabolism. Our knowledge of and ability to predict drug interactions have improved with growing understanding of substrates, inhibitors and inducers of cytochrome P450 (CYP-450) isoenzymes. These isoenzymes are a major determinant of the pharmacokinetic behavior of numerous drugs. In addition to inhibition and induction, microsomal drug metabolism is affected by genetic polymorphisms, age, nutrition, hepatic disease and endogenous chemicals. Prescribing physicians by understanding the unique characteristics of these isoenzymes may better anticipate and manage drug drug interactions.

Effect of cimetidine on hepatotoxicity induced by isoniazid-rifampicin combination in rabbits.

OBJECTIVE: To evaluate the hepatoprotective potential of cimetidine in hepatotoxicity induced by isoniazid-rifampicin combination in albino rabbits. METHODS: Six groups of six rabbits each were studied. Three groups received saline (control), isoniazid (50 mg/Kg/d) alone or isoniazid with rifampicin (100 mg/Kg/d) daily orally for 7 days. Other groups received intraperitoneal cimetidine (50 mg/Kg/d) alone or cimetidine (50 or 120 mg/Kg/d) along with isoniazid-rifampicin combination. Serum levels of liver enzymes were measured at baseline and on day 8 and liver histology was studied on day 8. RESULTS: Rabbits receiving isoniazid alone for 7 days showed no increase in serum ALT and AST levels, whereas those receiving isoniazid-rifampicin combination had a 3-4-fold increase in these levels (p=0.02). Animals receiving cimetidine pre-treatment did not show a significant increase in ALT and AST levels. Histological changes in the liver were more common with isoniazid-rifampicin combination than with isoniazid only. These changes were reduced in animals receiving low-dose cimetidine and prevented in those receiving high-dose cimetidine. CONCLUSION: Cimetidine in high dose can prevent hepatotoxicity induced by isoniazid-rifampicin combination.