the study was carried on 12-week old male , wistar albino rats weighing 150 - 200 g. the animals were housed in a group of six animals per cage and maintained at 20 - 30c and 50 - 55% humidity in a natural light and dark cycle , with free access to food and water and kept under standard conditions in an animal house facility approved by the committee for the purpose of control and supervision of experiments on animals . utmost care was taken to ensure that animals were treated in the most humane and ethically acceptable manner . on the day , of the experiment the femoral artery on one side was exposed , and a polyethylene catheter was inserted into the artery for recording abp . potency of the catheter was maintained with a heparinized saline solution ( 5000 iu m / l , v / v ) . the pressure recording system was calibrated with the help of a mercury manometer before each experiment . cannulation of the femoral vein of the other limb was performed to facilitate drug injection . rats were administered with different dilutions ( 9.5% , 19.0% , 28.5% , 38.0% , 47.5% , 57.0% , 66.5% , 76% ) of methanol systolic bp mean abp , and heart rate were recorded on a power - lab data acquisition system with a computerized analysis program . statistical analysis of the data were performed using one - way analysis of variance , where p < 0.05 were considered as significant , and was expressed as mean  standard error of the mean . on the day , of the experiment , rats were anaesthetized with the chloroform solution . the femoral artery on one side was exposed , and a polyethylene catheter was inserted into the artery for recording abp . potency of the catheter was maintained with a heparinized saline solution ( 5000 iu m / l , v / v ) . the pressure recording system was calibrated with the help of a mercury manometer before each experiment . cannulation of the femoral vein of the other limb was performed to facilitate drug injection . rats were administered with different dilutions ( 9.5% , 19.0% , 28.5% , 38.0% , 47.5% , 57.0% , 66.5% , 76% ) of methanol ( 95% v / v , i.v . ) . systolic bp mean abp , and heart rate were recorded on a power - lab data acquisition system with a computerized analysis program . statistical analysis of the data were performed using one - way analysis of variance , where p < 0.05 were considered as significant , and was expressed as mean  standard error of the mean . of all the dilutions of methanol used , there was a statistical significant decrease ( p < 0.05 ) , that is , maximum decrease , of diastolic bp from 124.64  5.39 to 62.30  11.9 mmhg observed at the methanol dilution of 66.50% . similarly , of all the dilutions of methanol used in our study , there was a statistical significant decrease ( p < 0.05 ) , that is , the maximum decrease , of systolic bp from 165.70  5.57 to 112.11  12.0 mmhg , and mean abp from 160.61  12.45 to 86.14  4.11 mmhg observed at the methanol dilution of 76.0% . the heart rate increased ( from 250 beat / s to nearly 275 beats / s ) following administration of all the methanol dilution from 19.0% till 76.0% of methanol dilution , however , a statistical significant increase ( p < 0.05 ) of heart rate was observed from 239.70  28.80 to 313.55  16.65 beat / s at the methanol dilution of 9.5% [ figures 1 - 4 ] . effect of different doses of methanol ( 95% v / v ) on diastolic blood pressure ( mmhg ) effect of different doses of methanol ( 95% v / v ) on systolic blood pressure ( mmhg ) effect of different doses of methanol ( 95% v / v ) on mean arterial blood pressure ( mmhg ) effect of different doses of methanol ( 95% v / v ) on heart rate ( beats / min ) the present study investigated the effect of methanol poisoning in rats administered at a different methanol concentration . in this study in rats , we observed a decrease in diastolic bp , systolic bp and mean abp albeit at different concentration of methanol . in methanol poisoning , low bp ( hypotension ) and respiratory arrest have been reported . previously , hemodynamic effects of successive intravenous infusions of 20% methanol in anesthetized , mechanically ventilated dogs have been assessed against any spontaneous changes occurring during saline infusions . about 130 - 200 mg/100 ml or higher blood methanol concentrations progressively decreased stroke volume and cardiac output , systemic bp and blood flow through femoral and common carotid arteries , while total peripheral resistance increased . death by cardiac arrest was reported to occur at blood concentrations exceeding 400 mg/100 ml . in our study , we observed an overall decreasing tendency of systolic bp , diastolic bp and mean abp with increasing concentrations of methanol though there were little fluctuations in bp . while , the heart rate remained consistently raised at all methanol dilution administered except the lowest concentration ( 9.5% v / v ) where , surprisingly , a greater increase in heart rate was noted . hence , this can be regarded as an outlier and ignored for making interpretation in this study . the increase in heart rate could be attributed to the compensatory mechanism for methanol induced hypotension , a major symptom of methanol poisoning . by the higher increase in heart rate itself is an independent predictor of cardiovascular , noncardiovascular , and total mortality in some population , leading to death . it was suggested that methanol poisoning potentially alters hemodynamic parameters , as previously , methanol overdose was reported to show changes in the electrocardiogram ( ecg ) wherein patient developed right bundle branch block in addition to left anterior fascicular block , paroxysmal atrial fibrillation and increased left ventricular end - diastolic and end - systolic dimensions . in another report by hazra et al . reported that the regression of ecg changes coincided with clinical improvement and suggested that they were caused by methanol poisoning . cardiac contractility and cardiac output were also reported to be reduced and arterial vasodilation develops , which might contribute to hypotension ventricular arrhythmia is often observed . acidosis has been a well - documented diagnosis during methanol intoxication , but it is unclear whether it is derived directly from formic acid or due to its secondary effects of inducing lactic acidosis . independent of the etiology of the acidosis , it has been widely reported that metabolic acidosis can lead to various adverse effects to the cardiovascular system . in one animal study with dogs , increased susceptibility of the heart to ventricular fibrillation was found during metabolic acidosis . in another animal study with rats , the authors concluded that acidosis produced a marked decrease in heart rate and an increase in p - r interval with no apparent effect on the duration of the qrs complex . methanol being a potent toxicant in humans has been reported to occur naturally at a low level in most alcoholic beverages without causing harm . however , illicit drinks made from  industrial methylated spirits  [ 5% ( v / v ) methanol : 95% ( v / v ) ethanol ] was reported to cause severe and even fatal illness . no - adverse - effect level for methanol has been poorly documented and , therefore , from the public health perspective , what should be the maximum concentration of methanol in an alcoholic drink that an adult human could consume without risking toxicity due to its methanol content is not widely known . in 2001 , paine and davan reported that if an adult takes 4  25-ml standard measures of a drink containing 40% alcohol by volume over a period of 2 h , the maximum tolerable concentration of methanol in such a drink should be 2% ( v / v ) by volume . however , they suggested that this value only allowed a safety factor of 4 to cover variation in the volume consumed and for the effects of malnutrition ( i.e. folate deficiency ) , ill health and other personal factors ( i.e. ethnicity ) . in contrast , according to the current european union general limit , 0.4% ( v / v ) methanol at 40% alcohol was reported to provide a greater margin of safety . in our study , we observed a consistent rise in heart rate starting after administration of 19% methanol dilution in rats indicating that the concentration lower than 19% could correspond to the safety margin of 0.4 - 2% ( v / v ) in clinical settings . the present study is consistent with previous studies suggesting that methanol ingestion leads to severe hypotension as observed from decrease in diastolic bp , systolic bp , and mean abp . however , severe increase of heart rate suggests activation of a compensatory mechanism to offset hypotension that eventually leads to death in methanol poisoning . hence , this study emphasizes the need to monitor all the hemodynamic parameters in accidental methanol poisoning . as , the present study is just a preliminary research work , and therefore it warrants further study to better manage methanol poisoning in actual clinical scenarios .