Effect of cyclooxygenase inhibitors in postoperative ileus: an experimental study

The aim of our study was to investigate the effect of various cyclooxygenase (COX) inhibitors (namely, indomethacin [a nonselective COX inhibitor], nimesulide [a partially selective COX inhibitor] and celecoxib [a highly selective COX inhibitor]) on postoperative ileus in rats. Equianalgesic doses of the three drugs were determined previously by formalin-induced hyperalgesia. Three comparative doses of the drugs were taken. After overnight fasting, a standardized laparotomy was performed on the rats. Bowel motility was determined by the charcoal meal test. The distance traveled by the charcoal meal was expressed as a percentage of the total length of the small intestine. The animals were pretreated intraperitoneally with either indomethacin (2.5, 5.0 and 10 mg/kg), nimesulide (10.0, 20.0 and 40 mg/kg), celecoxib (10.0, 20.0 and 40 mg/kg) or vehicle 1 h prior to the experiment. The lowest doses at which an increase in postoperative bowel motility occurred were 10 mg/kg of indomethacin and 20 mg/kg for both nimesulide and celecoxib. For equianalgesic doses it was noted that celecoxib was more effective than nimesulide or indomethacin in increasing postoperative bowel motility (52.15 +/- 1.08, 55.11 +/- 0.87 and 60.65 +/- 1.22 at the highest doses of indomethacin, nimesulide and celecoxib, respectively).

A comparison of non-tapering vs. tapering prednisolone in acute exacerbation of asthma involving use of the low-dose ACTH test

OBJECTIVE

To determine if there is a difference in early relapse rates and adrenal suppression between patients receiving an 8-day course of 40 mg/day prednisolone and those receiving an 8-day tapering course of prednisolone.

METHODS

This was a prospective, randomized, open clinical trial conducted in a tertiary care center. All asthmatic patients with exacerbation who were judged well enough for discharge home from the emergency department were eligible for participation. Patients with a history of chronic obstructive pulmonary disease, congestive heart failure, pneumonia, pneumothorax, or other pulmonary process and asthmatics already using inhaled or oral steroids within 2 weeks of admission to the emergency department were excluded. Patients on discharge were administered either on 8-day course of 40 mg/day prednisolone or an 8-day tapering course of prednisolone (tapering from 40 mg to 0 mg). Patients were asked to return on Day 12 for cosyntropin stimulated test and pulmonary function testing and on Day 21 for pulmonary function testing only.

RESULTS

A group of 13 patients treated with non-tapering course (40 mg/day) of prednisolone for 8 days were compared to a group of 13 patients treated with a tapering course (40 mg taper by 5 mg/day) for 8 days. There were no differences in the FEV1 percent predicted (Days 12 and 21), the incidence of relapse, or the incidence of adrenal suppression between the 2 groups.

CONCLUSION

In this small study, we found no significant difference in relapse rate or adrenal suppression between asthmatics receiving an 8-day tapering dose of prednisolone and those receiving 40 mg/day prednisolone upon discharge from the emergency department.

Effect of oral magnesium supplementation on experimental pre-eclampsia induced by prolonged blockade of nitric oxide synthesis in pregnant rats

Nitric oxide inhibitor L-NAME when given alone caused a significant rise in both systolic and diastolic pressure, an increase in 24 hr urinary protein excretion and reduction in weight of the litter as compared to control group. Supplementation of MgSO4 at lower dose (250 mg/kg) did not inhibit this pre-eclamptic effect of L-NAME; but in higher doses (500 and 750 mg/kg), it inhibited the pre-eclamptic action of L-NAME. The results suggest that administration of MgSO4 improves the foetal outcome and significantly prevents the development of symptoms of pre-eclampsia like hypertension and proteinuria.

Role of nitric oxide in experimental models of psychosis in rats

The aim of our study was to investigate the effects of the NO precursor L-arginine and the nitric oxide synthase inhibitor N omega-nitro-L-arginine (L-NORAG) on amphetamine-induced stereotypy, haloperidol-induced catalepsy and conditioned avoidance response (CAR) in rats. Amphetamine (3 mg/kg i.p.) was used for the induction of stereotypy, while for the induction of catalepsy and CAR, haloperidol (2 mg/kg i.p.) was used. This study was divided into 2 parts--acute administration of L-arginine (150 mg/kg i.p.) and L-NOARG (50 mg/kg i.p.) and chronic administration of L-arginine (150 mg/kg/day i.p.) and L-NOARG (50 mg/kglday i.p.) for 5 days. We found that L-arginine inhibited amphetamine-induced stereotypy and haloperidol-induced catalepsy, but intensified CAR. On the other hand, L-NOARG intensified stereotypy and catalepsy but inhibited CAR. Also, there was no significant difference between the scores of acute and chronic administration of L-arginine and L-NOARG. It is concluded from our study that nitric oxide produces conflicting results on various models of psychosis. L-arginine might be useful as an antipsychotic without causing extrapyramidal symptoms.

Drug related medical emergencies in the elderly: role of adverse drug reactions and non-compliance

BACKGROUND

Adverse drug reactions and non-compliance are important causes of admissions in the elderly to medical clinics. The contribution of adverse drug reactions and non-compliance to admission by the medical emergency department was analysed.

METHODS

A total of 578 consecutive elderly patients admitted to the medical emergency department were interviewed to determine the percentage of admissions due to adverse drug reactions or non-compliance with medication regimens, their causes, consequences, and predictors.

RESULTS

Eighty three (14.4%) of the 578 admissions were drug related: 39 (6.7%) caused by adverse drug reactions and 44 (7.6%) caused by non-compliance with medication. One hundred ninety two (33.2%) patients had a history of non-compliance. Factors associated with an increased risk of admission because of an adverse drug reaction were patients with diabetes or neoplasms, and patients using numerous different medications. Factors associated with a higher risk of hospitalisation because of non-compliance were poor recall of the medication regimen, seeing numerous physicians, female sex, polypharmacy, drug costs, and switching over to non-conventional forms of treatment.

CONCLUSION

Many elderly admissions are drug related, with non-compliance accounting for a substantial fraction of these. Elderly people at high risk of suffering a drug related medical emergency are identified and suitable interventions may be planned by the healthcare policymakers to target them.

Pattern of use and pharmacoeconomic impact of antihypertensive drugs in a north Indian referral hospital

OBJECTIVE

The current study was designed to investigate drug utilisation and the pharmacoeconomics of hypertension in the hypertension clinic of a tertiary-care hospital.

METHODS

The study was conducted in patients attending the hypertension clinic of Nehru Hospital, Postgraduate Institute of Medical Education and Research, Chandigarh, India. A survey of prescriptions was carried out, and the information obtained was further corroborated by seeing the medical records as well as patient interviews.

RESULTS

A total of 1,076 prescriptions were evaluated. Beta-adrenoceptor-blocking agents (51%), calcium antagonists (47%) and angiotensin-converting enzyme inhibitors (46%) were the most popular drugs. The utilisation of thiazides was less than expected. Combination therapy was used more commonly than monotherapy (53.8% vs 46.7%). Oral hypoglycaemic agents and lipid-lowering agents were commonly co-prescribed along with antihypertensive medications. About 30% of drugs were prescribed by generic name and 90% were from the national essential drugs list. Of the per capita income, 10.6% was spent on the treatment of hypertension. The mean monthly cost of various drugs ranged between US $0.8 and US $6.6. A total of 91 adverse drug reaction (ADRs) were encountered in the study; the added cost of treatment of these ADRs was US $211.

CONCLUSION

In general, the treatment guidelines for hypertension were followed in our hospital. The utilisation of thiazides was an area requiring improvement. The cost of treatment of hypertension was substantial and imparted a significant economic burden on the patients.

A randomized parallel trial of topical aspirin-moisturizer solution vs. oral aspirin for acute herpetic neuralgia

BACKGROUND

In this study, the efficacy of oral aspirin vs. topical aspirin in moisturizer (Vaseline Intensive Care Lotion) was studied in an open, randomized, parallel trial in patients with acute herpetic neuralgia.

METHODS

Thirty patients were evaluated in the trial, with 15 in each group. The patients were randomized to receive either oral aspirin, 375-750 mg three times a day, or 75 mg topical aspirin/mL of moisturizer (5-10 mL, depending on the extent of involvement), three times a day, for 21 days. Pain was assessed daily by means of a self-rating visual analog scale and physician assessment. In addition, the skin and plasma levels of aspirin were measured in both groups.

RESULTS

The mean time to onset of pain relief was 44 min with topical aspirin and 110 min with oral aspirin. The mean duration of pain relief after a single application of topical aspirin was 5.4 h, whereas it was 3.5 h with oral aspirin. The mean visual analog scale scores for pain with oral aspirin decreased from 68.2 +/- 6.1 on day zero to 43.1 +/- 8.7 on day 21, which was not significant compared with the baseline score. With topical aspirin, the baseline pain score was 77.5 +/- 3.7 and decreased to 6.8 +/- 3 on day 21 (P < 0.001 compared to the baseline score and compared to oral aspirin). The mean plasma and skin levels of aspirin following oral administration were 16.21 +/- 1.1 microg/mL and 1.97 +/- 0.3 microg/mm2, respectively. After topical administration, the mean plasma level of aspirin was 2.29 +/- 0.5 microg/mL (P < 0.01 vs. oral aspirin) and the skin level was 5.96 +/- 0.4 microg/mm2 (P < 0.05 vs. oral aspirin). Treatment tolerance was excellent in both groups.

CONCLUSIONS

This trial has demonstrated that topical aspirin in moisturizer is clearly superior to oral aspirin in relieving the pain of acute herpetic neuralgia, and that the analgesic activity of aspirin is largely due to its local effect.

Anticonvulsant activity of omeprazole in rats

Omeprazole has long been used as an effective agent to treat peptic ulcer. Recent studies have shown that in addition to inhibiting the H(+)-K(+)ATPase, it also inhibits carbonic anhydrase (CA) types I, II and IV. This led us to investigate its anticonvulsant effect in a rat model of electroconvulsion. Since other carbonic anhydrase inhibitors like acetazolamide induce tolerance upon repeated use, we tested the tolerance potential of omeprazole upon repeated administration of up to 1 week. The animals were divided into four groups receiving normal saline, omeprazole 0.5, 1 or 2 mg/kg intraperitoneally. CC(50), i.e. the threshold current inducing tonic hind limb extension in 50% of the rats was established using a technoconvulsometer which delivers currents of varying intensity via ear clip electrodes. The CC(50) was established 30 min after injection of omeprazole. In another group of rats, omeprazole 2 mg/kg was given for 6 days and the CC(50) determined on days 0, 1, 3 and 6. Also the concentration of omeprazole in the brain was determined using high performance liquid chromatography. The CC(50) in vehicle-treated rats was 98 mA, which increased to 126, 135 and 162 mA with 0.5, 1 and 2 mg/kg of omeprazole, respectively. On repeat-dose studies the CC(50) on day 0 was 96 mA, on day 1 166 mA, on day 3 129 mA and on day 6 102 mA. The average brain concentration of omeprazole was 53.2+/-6.9 ng/g of brain tissue. In conclusion, this study has shown omeprazole to be an effective anticonvulsant, but rapidly develops tolerance to its anticonvulsant action. This study can stimulate interest in the development of agents with dual function -- inhibition of CA as well as the accompanying Na(+)-K(+) ATPase -- and such agents may prove to be effective anticonvulsants without exhibiting tolerance.

Patterns of use of unconventional therapies in the medical outpatient department of a tertiary care hospital in India

Unconventional, alternative or unorthodox systems of treatment have become increasingly popular in recent years. We interviewed patients visiting the Internal Medicine outpatient department (OPD) for a period of 6 months regarding their use of unconventional therapies. Overall 76% of patients visiting the OPD had used one or more of the unconventional therapies in the past 1 year. Homeopathy was found to be the most frequently used alternative therapy (38.6%). A large number of patients used more than one unconventional therapy. Digestive problems, backache, joint pains and bronchial asthma were the most frequent conditions for which alternative therapies were used. Most patients who used alternative therapies used them on their own, without actually visiting a provider of such therapies. Because of the widespread use of alternative systems of medicine, efforts to enhance understanding about these forms of treatment have to be made.

An audit of the use of antirheumatic drugs in a north Indian referral hospital

OBJECTIVE

This study was conducted with the aim of auditing the pattern of use of antirheumatic drugs in a tertiary care hospital in Northern India.

METHODS

The study was carried out in 1000 patients recruited sequentially from the clinic for a period of 1 year (January to December 1999). Patient data such as age, sex, income, family size, diagnosis, duration of illness, drugs prescribed/duration, adverse drug reaction were noted and used to calculate core drug use indicators and pattern of drug use.

RESULTS

The pattern of drug use was in accordance with the standard practices followed internationally. In rheumatoid arthritis the most common prescriptions were for non-steroidal antiinflammatory drugs (NSAIDs) alone, followed by the combination of NSAIDs, disease modifying agents (DMARDs) and steroids. Of the NSAIDs diclofenac was the most frequently prescribed drug, while chloroquine was the most commonly used DMARD. The most commonly seen adverse drug reactions were gastritis, Cushings syndrome and decreased visual acuity.

CONCLUSION

In conclusion, this study has demonstrated that in this clinic, the pattern of use of antirheumatic drugs follows standard guidelines.

Effect of duration of pilocarpine-induced status epilepticus on subsequent cognitive function in rats

The aim of this study was to determine the effect of the duration of pilocarpine-induced status epilepticus (SE) on subsequent cognitive function in rats. SE was induced by pilocarpine (320 mg/kg i.p.) and was terminated by injection of 1 mg/kg diazepam at 30, 60 and 90 min in 3 groups of 10 rats each. Cognitive function was tested by a passive avoidance task and was assessed at the baseline and on days 1, 7, 14 and 21 (post SE). It was found that cognitive function was disrupted on days 7, 14 and 21 post SE in rats who had SE for 60 and 90 min, whereas it was not affected in rats that had 30 min of SE. Hence, the duration of SE may affect future cognitive performance and mandates emergency treatment.

A meta-analysis of controlled clinical trials comparing low-molecular weight heparins with unfractionated heparin in unstable angina

BACKGROUND

Unfractionated heparin has been used extensively for the treatment of unstable angina/non-Q wave myocardial infarction but it has several disadvantages. Low-molecular weight heparins are now recommended although they are 3-5 times costlier than unfractionated heparin since they are convinient to administer and do not require activated thromboplastin time monitoring. Whereas enoxaparin, a low-molecular weight heparin, has been demonstrated to be superior to unfractionated heparin, the results of other low-molecular weight heparins have not been so convincing.

METHOD AND RESULTS

Through manual, MEDLINE and EMBASE search, we identified five randomized trials (excluding enoxaparin trials) that compared low-molecular weight heparins with unfractionated heparin in unstable angina. The prespecified efficacy end point of interest included a composite of death, myocardial infarction, recurrent angina and urgent revascularization. The safety end point was taken as a composite of major hemorrhage, minor hemorrhage, thrombocytopenia, allergic reaction and any other adverse event. We calculated odds ratio (95% confidence interval) for each trial for the composite end point, and the pooled odds ratio (95%) confidence interval) was calculated using two established methods of meta-analysis, the Mantel-Haenszel-Peto method and the DerSirmonian-Laird method. Both the methods yielded similar odds ratio (95% confidence interval). Separate odds ratio were calculated for efficacy and safety end points. There was a nonsignificant reduction in the incidence of the composite efficacy end point: the odds ratio (95% confidence interval) was 0.83 (0.70-0.99: p=0.08). The odds ratio (95% confidence interval) for the safety data was 0.78 (0.69-1.26: p=0.33).

CONCLUSIONS

No statistically significant difference was observed when the efficacy and safety of low-molecular weight heparins were compared with those of unfractionated heparin. A cost-effectiveness analysis of low-molecular weight heparins versus unfractionated heparin must be done urgently to establish more firmly the place of low-molecular weight heparins in the management of unstable angina.

A randomized trial to compare the efficacy, safety, cost and platelet aggregation effects of enoxaparin and unfractionated heparin (the ESCAPEU trial)

OBJECTIVE

To compare the efficacy, safety, cost and effects on platelet aggregation of unfractionated heparin and low-molecular weight heparin in unstable angina patients.

PATIENTS AND METHODS

Ninety-three patients with unstable angina were randomized to receive either unfractionated heparin (UFH) or enoxaparin in an open design clinical trial with blinded end point evaluation. The effects of the heparins on platelet aggregation were also compared.

RESULTS

The composite end point of myocardial infarction, cardiac death, recurrent angina and need for intervention was observed in 62% of patients treated with UFH and in 37% of patients treated with enoxaparin (RR 1.7, 95% CI 0.75 to 3.71, p = 0.04). There was no difference in the frequency or severity of adverse events. A cost-effectiveness analysis showed both the heparins to be similar. Platelet aggregation was inhibited to a greater extent by UFH when compared to enoxaparin.

CONCLUSIONS

Enoxaparin appears to be superior in efficacy to UFH and similar to UFH in safety. No difference in costs was detected in this study. The greater inhibition of platelet aggregation observed in the case of UFH compared to enoxaparin indicates that there may be more bleeding complications with UFH.

Drug-related visits to the medical emergency department: a prospective study from India

OBJECTIVE

To analyze the contribution of adverse drug events (ADEs) to the overall number of visits to the medical emergency and to determine the proportion of events leading to hospital admissions.

PATIENTS AND METHODS

All visits to the medical emergency were recorded in a prospective, non-interventional design study over a period of 8 months. The ADEs were divided into 5 categories: adverse drug reactions (ADRs), drug interactions, patient non-compliance, physician non-compliance, and drug overdose. The cases were then followed-up to assess the prorportion of ADEs lead to hospitaliztion.

RESULTS

A total of 4764 patients were included in the study. 5.9% of all visits were considered to be drug-related. The highest percentage of ADEs was observed in the age group less than 20 and more than 80 years. ADRs accounted for 45% of all ADEs, followed by patient non-compliance (28%). Patient and physician non-compliance were the main causes of drug-related hospital admissions. 52% of all ADE-related visits and 55% of ADE-related admissions were considered to be preventable. Non-steroidal antiinflammatory agents, oral hypoglycemics and antitubercular drugs were responsible for 37% of all ADRs. Non-compliance was mainly seen in hypertensives, asthmatics and epileptics.

CONCLUSION

ADEs account for a sizable proportion of all visits to a medical emergency unit and some are serious enough to require hospitaliztion. A large number of ADE-related visits and admissions are preventable which highlights the importance of public education on the proper use of drugs, and also the need for regulation of the practice of unregistered medical practitioners in developing countries.

Effect of calcium antagonists on stress-induced rise in blood pressure and heart rate: a double-blind, placebo-controlled study

OBJECTIVE

The current study was designed to evaluate the effect of treatment with calcium antagonists on stress-induced increases in blood pressure and heart rate. SUBIECTS, MATERIAL AND METHODS: Two models of stress were chosen, cold stress and isometric handgrip exercise. Six healthy volunteers were randomized to receive amlodipine (5 mg), lacidipine (4 mg) for a two-day period in a double-blind, crossover design. Thirty hypertensive patients received the same treatment for a period of one week in a double-blind, parallel design. The effects of stress on blood pressure and heart rate were taken at baseline and after drug treatment.

RESULTS

Cold stress and handgrip exercise significantly increased the systolic and diastolic blood pressure as well as the heart rate. In normotensive volunteers, the resting heart rate and blood pressure were not altered by the drugs. The increase in systolic and diastolic blood pressure produced by cold stress and isometric exercise were unchanged by amlodipine and lacidipine. In hypertensive patients, both drugs reduced the resting blood pressure (p < 0.05). As in normotensive individuals, the pressor response to stress was not altered by the drugs.

CONCLUSION

Cold stress and handgrip exercise produced a significant rise in blood pressure and heart rate in normotensive volunteers and patients with hypertension. Cardiovascular reactivity to cold stress and handgrip exercise is not altered by the administration ofamlodipine and lacidipine.

Anticonvulsant effect of nimodipine alone and in combination with diazepam and phenytoin in a mouse model of status epilepticus

The effect of nimodipine alone and in combination with diazepam or phenytoin was tested in the electroshock-induced mouse model of status epilepticus. Status epilepticus was induced by transauricular electrical stimulation with a stimulus of 15 mA at 0.5, 3, 10, 20 and 30 min, starting half an hour after intraperitoneal administration of vehicle/drug. The median effective doses of diazepam and phenytoin alone and in combination with a fixed dose of nimodipine (24 mg/kg) was calculated. The ED50s of diazepam and phenytoin were found to be 10.5 and 9 mg/kg, respectively. When nimodipine was combined with diazepam or phenytoin, the ED50 values decreased to 3.77 mg/kg and 7.15 mg/kg, respectively. The severity of seizures was also decreased by combination with nimodipine as compared to diazepam and phenytoin given alone. To study the effect of nimodipine on psychomotor impairments produced by diazepam and phenytoin three tests were performed: rotarod, behavioral despair and hole board. Nimodipine did not show protective effects on its own but potentiated the anticonvulsant effects of diazepam and phenytoin. Furthermore, the combination of nimodipine with diazepam and phenytoin produced lesser impairment of psychomotor functions.

Tolerance to and Withdrawal from Anticonvulsant Action of Diazepam: Role of Nitric Oxide

Tolerance to the anticonvulsant action of diazepam as a result of central nervous system adaptation limits its use in epilepsy. In Wistar rats, diazepam 5 mg/kg ip twice daily produced tolerance to its anticonvulsant action in 6 days. Abrupt withdrawal caused hyperexcitability. Tolerance manifested as a decrease in seizure threshold to near-control values, while withdrawal hyperexcitability was evidenced by a significant decrease in seizure threshold below the control value. This effect was seen both in the "same group design" and "separate group design." L-Arginine (a donor of nitric oxide) and N(omega)-nitro-L-arginine (an inhibitor of nitric oxide synthase) were given in doses of 150 and 8 mg/kg, respectively, on Days 1, 3, and 6 along with diazepam in the same group design. Their role in preventing the development of tolerance to the anticonvulsant effect was seen on Days 1, 3, and 6. Withdrawal hyperexcitability was seen on Days 1, 2, and 4 after cessation of drug therapy. Both electroshock and pentylenetetrazole (PTZ) infusion were used as models of epilepsy, and seizure thresholds were determined. The up and down method of A. W. Kimball, W. T. Burnett, and G. D. Doherty (Radiat Res 1957;7:1-12) was used to determine the seizure threshold in cases of electroshock-induced seizures. L-Arginine, when administered with diazepam, was found to inhibit tolerance as well as withdrawal hyperexcitability. N(omega)-nitro-L-arginine did not prevent the development of tolerance or withdrawal hyperexcitability in the electroshock model, while in the PTZ model inhibition of nitric synthesis prevented withdrawal hyperexcitability but had no effect on the development of tolerance.

Analgesics for pediatric use

The use of nimesulide is increasing and recently, concerns have been raised regarding its hepatotoxicity, especially in children. At least two deaths due to fulminant hepatic failure have been attributed to nimesulide. In India, nimesulide has been approved and about twelve pediatric preparations are available. Lack of effective postmarketing surveillance means that adverse drug reactions may not be picked or reported. Therefore, quick approval of those drugs for which substitutes are available may not be desirable in India and in other developing countries.

Effect of acute and chronic administration of L-arginine on morphine induced inhibition of gastrointestinal motility

Effect of acute and chronic administration of L-arginine on morphine induced gastrointestinal inhibition was tested in rats. In the test for acute effect, L-arginine (200 mg/kg, i.v.) was given 10 minutes before the charcoal meal test. In the test for chronic effects, L-arginine (200 mg/kg, i.v.) was given twice a day for 4 days. Charcoal meal test was done on the fifth day. Morphine was administered 45 minutes before the charcoal meal test. Results showed that acute administration of L-arginine did not affect the morphine's action on the GIT. In contrast, chronic administration of L-arginine reversed the morphine induced decrease in gastrointestinal motility. The reversal was however, not complete. This data suggests that inhibition of NO may be one of the mechanism of morphine induced constipation.

Effect of oral magnesium supplementation on blood pressure, platelet aggregation and calcium handling in deoxycorticosterone acetate induced hypertension in rats

OBJECTIVE

To study the effect of oral magnesium supplementation on blood pressure, platelet aggregation and platelet calcium handling in deoxycorticosterone acetate (DOCA)-induced hypertension in rats.

DESIGN AND METHODS

Rats were divided into four groups of 20 each. Drug treatments were given for a 6-week period. Control rats were vehicle treated. In the second group, DOCA, 15 mg/kg, was injected subcutaneously twice weekly with 1% NaCl used instead of drinking water. The third group was given magnesium oxide (MgO), 1 g/kg daily, orally by gavage. The fourth group was given MgO along with DOCA and 1% NaCl. Blood pressure and heart rate were measured weekly. Platelet aggregation, intracellular calcium, calcium uptake and calcium efflux studies were performed at the end of sixth week. Serum magnesium concentration, plasma levels of reactive nitrogen intermediates (RNI) and citrulline were also measured

RESULTS

There was a significant rise in blood pressure in the DOCA-treated rats. Magnesium prevented the gradual rise in blood pressure when given along with DOCA, but had no effect in normotensive rats. Heart rate did not show any significant change. Platelet aggregation was significantly reduced in all the treatment groups compared to the control group. DOCA treatment produced a significant increase in the intracellular calcium concentration as well as the calcium uptake compared to the control group. Magnesium supplementation inhibited the increased intracellular calcium concentration and calcium uptake in DOCA-treated rats. RNI and citrulline levels were elevated in all the treatment groups. Serum magnesium levels were significantly higher in the magnesium-treated and DOCA plus magnesium-treated rats.

CONCLUSIONS

Magnesium supplementation prevents blood pressure elevation in DOCA hypertensive rats. These effects are associated with inhibition of platelet calcium uptake and decreased intracellular free calcium concentration.

Tolerance and withdrawal to anticonvulsant action of clonazepam: role of nitric oxide

The use of clonazepam in the long-term treatment of epilepsy is greatly inhibited by its capacity to induce tolerance and dependence. A means of preventing or minimizing the tolerance and dependence inducing properties is required. Here the role of nitric oxide in preventing the development of tolerance and withdrawal hyperexcitability was studied. In Wistar rats, clonazepam at a dose of 0.25 mg/kg i.p. twice daily produced tolerance to its anticonvulsant action in 28 days. After sudden cessation of therapy it produced hyperexcitability. Tolerance was shown by a decrease in seizure threshold to near control value while withdrawal hyperexcitability was evidenced by a significant decrease in seizure threshold below the control value. L-Arginine (a donor of nitric oxide) and N omega-nitro-L-arginine (an inhibitor of nitric oxide synthase) were given in doses of 150 mg/kg and 8 mg/kg, respectively on day 1, 3, 7, 14, 21 and 28 with clonazepam. Withdrawal hyperexcitability was seen on day 1, 2 and 4 after cessation of drug therapy. Electroshock was used as a model of epilepsy and seizure thresholds were determined by an up and down method of Kimball et al. L-Arginine was found to inhibit the development tolerance as well as withdrawal hyperexcitability when administered with clonazepam while N omega-L-arginine did not prevent either the development of tolerance or withdrawal hyperexcitability in the electroshock model. In the PTZ model, however, L-arginine had no effect on the anticonvulsant action and withdrawal hyperexcitability while inhibition of nitric oxide synthesis prevented withdrawal hyperexcitability in PTZ-induced seizures.

Effect of muscarinic receptor agonists on animal models of psychosis

The purpose of this study was to determine the effects of muscarinic receptor agonists on models of psychosis in rats. A battery of three tests, catalepsy (haloperidol-induced) augmentation, amphetamine-induced stereotypy antagonism and conditioned avoidance response were used. Both muscarinic receptor agonists physostigmine and pilocarpine produced similar results. They dose-dependently augmented the haloperidol-induced catalepsy, inhibited amphetamine-induced stereotypy behavior and inhibited the conditioned avoidance response. Results demonstrate that muscarinic receptor agonists have actions similar to those of dopamine receptor antipsychotic drugs in animal models, suggesting that muscarinic receptor agonists may be used as adjuvant drugs in the treatment of psychosis.

Anticonvulsant profile of ondansetron in rats

Recent studies have shown the involvement of 5-hydroxytryptamine (5HT) in the pathogenesis of epilepsy. Hence it was decided to investigate the effect of the 5HT3 receptor antagonist ondansetron against maximal electroshock (MES)-induced seizures in rats. Also, the anticonvulsant activity of ondansetron in combination with phenytoin and its effect on the cognitive deficits induced by phenytoin were studied. MES was induced through ear-clip electrodes using a current strength of 150 mA for 0.2 second. The index of protection was taken as the inhibition of tonic hindlimb extension. The ED25 and ED16 doses of ondansetron were combined with subanticonvulsant doses of phenytion, i.e., 6 and 3 mg/kg. The retention latencies in the passive avoidance task (PAT) were assessed on Days 1 and 21 of chronic administration of ondansetron alone, phenytoin alone, and ondansetron in combination with phenytoin. The ED50 of ondansetron was found to be 1.05 (0.51-2.2) mg/kg. The combination of ondansetron with phenytoin had a potentiating effect against MES. Also, the retention latencies in the PAT of ondansetron alone and ondansetron in combination with phenytoin were significantly higher than that of phenytoin alone. Thus, ondansetron has potent anticonvulsant activity in rats and further potentiates the anticonvulsant activity of phenytoin. Also, it attenuates the cognitive dysfunction induced by phenytoin and merits further research for its mechanisms.

Role of nitric oxide in electroshock and pentylenetetrazole seizure threshold in rats

There are contradictory reports on whether nitric oxide (NO) is a proconvulsant or anticonvulsant. Hence a study was designed to investigate the effect of NO donor l-Arginine and NO synthesis inhibitor N omega-nitro-L-arginine (NOARG) on electroshock- and pentylenetetrazole (PTZ)-induced seizure threshold in rats. L-arginine was tested in three doses (75, 150 and 300 mg/kg), and NOARG was administered in doses of 4, 8 and 16 mg/kg. L-Arginine increased the intensity of current required to produce a threshold seizure, whereas NOARG had the opposite effect. In PTZ-induced seizures, L-arginine significantly decreased the dose of PTZ required to produce a threshold seizure, while NOARG increased it. Hence, it was concluded that NO synthase inhibition had the opposite effect in electroshock- and PTZ-induced seizures, meriting further studies on the mechanism of effect.