الفهرس 
Chapter I : IntroductionOnly 14 pages are availabe for public view
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Abstract
The present work was performed to investigate some pharmacodynamic effects of amikacin. It was divided into two types of experiment, in vitro and in vivo experiments. The in vitro experiments were applied to investigate the effect of amikacin on isolated smooth, cardiovascular muscles and neuromuscular preparations. Smooth muscles preparations such as gastrointestinal (guinea pig’s ileum, rabbit’s duodenum, rat’s colon and rat’s fundic strip) , rat’s uterus and guinea pig’s tracheal chain. Cardiovascular muscles preparations such as guinea pig’s auricles, rabbit’s heart and rabbit’s aortic strip. Neuromuscular preparations such as frog’s gastrocnemius muscle sciatic nerve, frog’s rectus abdominis muscle and rat’s phrenic nerve hemi diaphragm . The in vivo experiments were applied to investigate the effect of amikacin on blood pressure and rate of respiration in anaesthetized dog, analgesic activity of amikacin in mice and antipyretic effect of amikacin in rats. Effect of amikacin on electrocardiograph parameters in conscious rabbits, biochemical effects in rats and histopathological changes in kidneys and liver of rats were also investigated.
Amikacin in concentration lower than 80µg / ml bath had no effect on guinea pig’s ileum, while 156 to 312 µg/ml baths caused slight inhibition in the force of contraction of guinea pig’s ileum. Higher concentrations (625 to 1250 µg/ml bath) caused marked inhibition in the force and rate of contractions. Complete relaxation was achieved by addition of 2500 µg of amikacin / ml bath.
Concentrations of amikacin from 10-20 µg /ml bath had no effect on the duodenal motility of rabbits. Concentrations from 40 to 80 µg/ml bath caused slight inhibition in the force of contraction. Concentrations from 156 to 625 µg /ml bath induced marked inhibition in the force of contraction of isolated
Rabbit’s duodenum. Complete relaxation was achieved by a concentration of 1250µg /ml bath.
Amikacin in concentrations at 80 µg/ml bath had no effect on the rat’s colon motility. Concentrations of amikacin at 156 µg/ml bath caused slight inhibition in the force of contraction. Concentrations of amikacin from 312 to 625 µg/ml bath caused marked inhibition in the force and rate of contraction. Complete relaxation was achieved by concentration of 1250 µg/ml bath. The inhibitory effect of amikacin on isolated intestinal smooth muscle preparations appeared to be attributed to its direct effect, which proved by addition of acetylcholine as cholinergic agonist, nicotine sulphate in small concentration as ganglionic stimulant to rabbit’s duodenum, guinea pig ΄s ileum and rat’s colon caused a marked stimulation in the presence of amikacin. Moreover, amikacin induced its intestinal relaxant effect even after complete blockage of Alfa adrenergic receptors by phentolamine, therefore these results proved that the effect of amikacin seemed to be mostly through a direct inhibitory effect on the intestinal smooth muscle i.e myogenic effect.
Amikacin in concentrations lower than 80 µg/ml bath had no effect on the motility of rat’s fundic strip. Amikacin in concentrations of 156 µg/ml bath caused slight inhibition of the motility of rat’s fundic strip. Amikacin in concentrations of 312 to 625 µg/ml bath caused marked inhibition of the motility of rat’s fundic strip. Complete relaxation was produced by the concentration of 1250 µg/ml bath. The effect of histamine (2 µg/ml bath) was not able to produce its stimulant effect in presence of amikacin (625 µg/ml bath), so amikacin appeared to have an antihistaminic like effect.
Amikacin concentrations from 20 - 40 µg/ml bath had no effect in different stages of sex cycle (estrus, early pregnant, and late pregnant) while at (non estrus) amikacin at concentration of 20 - 40 µg/ml bath has slight inhibition in the force of contraction. amikacin in concentration of 60-80 µg/ml bath had marked inhibition on the isolated uterus in stages of non estrus and in early pregnant while in estrus and late pregnant it induced a slight inhibition in the force at contraction of amikacin 80 µg/ml bath.. Amikacin concentrations at 125 µg/ml bath produced complete relaxation of the myometrium in the non estrous, estrus ,early pregnant and late pregnant stages.The site of action of amikacin on the isolated uterus appeared to be myogenic in nature due to its direct effect on the myometrium , which proved by the addition of acetylcholine in a small concentration (0.25µg/ml bath) produced its stimulatory effect in the presence of amikacin and the amikacin produced its relaxant effect on the uterus after its stimulation with 1µg propranolol /ml bath.
All tested concentrations of amikacin did not induce any response on isolated guinea pig’s tracheal chain and rabbit’s aortic strip. Amikacin blocked the stimulant effects of histamine and nor adrenaline on isolated tracheal chain and aortic strip respectively due to its direct effect on these tissues.
Amikacin in concentrations smaller than 156 µg/ml bath had no effect on isolated guinea pig’s auricle. Concentrations from 312 to 625 µg/ml bath induced slight inhibition in the force of contraction. Concentrations from 1250 to 2500 µg/ml bath produced marked inhibition in the force of contraction of the auricles; the inhibitory effect of amikacin was referred to its direct myogenic effect on this tissue, which proved by addition of adrenaline (1 µg/ml bath) induced its stimulatory effect in the presence of amikacin (2500 µg/ml bath). Amikacin (2500 µg/ml bath) was able to produce its inhibitory effect in the presence of atropine sulphate (0.1 µg/ml bath). This inhibitory effect might be attributed to the reduction of cellular calcium content in a dose dependant manner.
Amikacin in the concentrations lower than 80 µg/ml canula induced no effects on the isolated rabbit’s heart. The concentrations from 80 to 125 µg/ml canula produced slight inhibition in the force of contraction. The concentrations from 156 to 312 µg/ml canula produced marked inhibition in the force of contraction and 625 µg/ml canula caused complete inhibition in the force .The inhibitory effect of amikacin was not referred to either β1 adrenergic blocking effect or cholinergic stimulant effect due to amikacin at (312 µg/ml canula ) was able to produce its inhibitory effect in the presence of atropine sulphate (25 µg/ml canula) .and isoprenaline ( 5x 10-4m) can produce its stimulatory effect in the presence of amikacin at 312 µg/ml canula , so its inhibitory effect referred to its direct myogenic effect, which attributed to reduction of cellular calcium content in a dose dependant manner, where amikacin replace calcium from lipid monolayer on the superficially bound calcium, so the loss of superficially bound calcium was accompanied by a decline of the contractile force by 40-90 %.
Amikacin in concentrations lower than 80 µg/ml bath had no effect on isolated frog’s gastrocnemius muscle. Concentrations of 80 and 125 µg/ml bath caused slight neuromuscular blockade. Concentrations of 156 and 312 µg/ml bath induced marked inhibition in the force of muscular twitches of frog’s gastrocnemius muscle which was less potent than that induced by procaine hydrochloride (2 %). This indicated that, amikacin had a dose dependant neuromuscular blocking effect on the isolated frog’s gastrocnemius muscle which was nearly similar to the action of procaine. The effect was attributed to the local anesthetic activity of amikacin on the sciatic nerve as well as its calcium antagonistic effect.
On the isolated frog’s rectus abdominis muscle, Concentrations of amikacin below 10 µg/ml bath had no effect. Concentration of 10 µg/ml bath caused slight decrease in the contracture in the presence of acetylcholine in concentration of 5 µg/ml bath. Concentrations of 20 µg/ml bath caused marked decrease of the contracture and complete blockade was produced in the presence of 40 µg/ml bath of amikacin.
On isolated rat’s phrenic nerve hemidiaphragm, amikacin at concentrations below 5 µg/ml bath had no effect, while concentrations of 5 and 10 µg/ml bath caused mild inhibition in the force of contraction. The concentration at 20 µg/ml bath produced marked inhibition in the force. Complete neuromuscular blockade was achieved by 40 µg/ml bath. Amikacin did not impair the stimulatory effect of acetylcholine and neostigmine on this preparation. Therefore, the neuromuscular blocking effect of amikacin seemed to be attributed to two mechanisms, the blockade after indirect stimulant which was due to local anesthetic effect of amikacin .This was responsible for blocking of conduction through sciatic and phrenic nerve. The blocking activity of amikacin after direct stimulation might be attributed to the calcium ions antagonistic effect of amikacin.
Intravenous injection of amikacin in dose 9.33 mg/ kg.b.wt.had no effect on blood pressure and respiration while in dose 14 mg/kg. body weight had produced hypotensive effect without effect on respiration in anaesthetized dogs .The hypotensive effect of amikacin did not attributed to cholinomimetic or alfa adrenergic blocking effect , as 14 mg/kg. body weight induced a hypotensive effect after intravenous injection of atropine sulphate (1 µg/kg body weight). Nor adrenaline 3 µg/kg body weight produced its hypertensive effect after injection of 14 mg/kg body weight of amikacin
Single intramuscular injection of 16.33 mg/kg.b.wt. induced a decrease in duration of PR interval and P-wave without significant changes occurred in its amplitude, QRS Complex and T- wave revealed that decrease in their amplitude. There is significant decrease in heart rat begin at 2 hours till 4 hours after injection.While at dose 24.3 mg/kg.b.wt. revealed that there was significant decrease in amplitude of P-wave , QRS Complex and T- wave and there was significant decrease in PR interval at 2 hours till 8 hours after injection while there was significant increase in ST, QT interval and there was significant decrease in heart rate begin at half hour till 4 hours after injection.
Intramuscular injection of amikacin in mice at a dose of 50 and 73.5 mg/kg body weight induced a highly significant analgesic effect after one hour and half after intramuscular injection of the two doses of amikacin respectively and continues along time of the experiment which was indicated by the longer reaction time in treated than control group.
Intramuscular injection of amikacin to rats in a dose of 31.5 mg./kg. body weight had significant antipyretic effect after 1.5 hours after administration while in amikacin in dose of 47.25 mg/ kg.body weight had significant antipyretic effect after 1 hour after administration which compared with control group. Amikacin produced direct vasodilatation action both in vitro (isolated aortic strip) and in vivo (hypotension). These two actions propose the peripheral mechanism of action of amikacin as antipyretic.
Intramuscular injection of amikacin in doses of 100 and 300 mg of amikacin per kg body weight daily for 5 days induced significant increase in the urea concentration in serum with significant decrease in its concentration in urine which became highly significant at 5th day of administration of amikacin in both groups of tested drug in albino rats and it become normal level at 9th day( 4th day post last injection ) in group A in serum and urine while in group B its concentration become decrease at 7th day ( 2nd day post last injection) and 9th day( 4th day post last injection) than in 5th day in serum and become increases in 9th day than 7th and 5th day in urine .also the obtained results revealed there was significant decrease in the urea clearance in both groups of experiment which appeared in 5th day to 7th day ( 2nd day post last injection) in group A while appeared from 3rd day of administration of amikacin to 9th day( 4th day post last injection) in group B. Intramuscular injection of amikacin in doses of 100 and 300 mg of amikacin per kg body weight per day for 5 days revealed that amikacin has significant increase in creatinine concentration in serum and significant decrease in its concentration in urine only in group B which began in 3rd day of administration of drug till 9th day( 4th day post last injection) with high significant appeared in 5th day after administration of amikacin with significant decreases in creatinine clearance in group B . This effect might be attributed to renal lesions which appeared histopathologically in its early stages in group A were manifested by cloudy swelling and vascular degeneration of lining epithelium of renal tubules while in group B kidneys of rat revealed sever renal lesions which manifested by thrombosis of some renal vessels with diffuse coagulative necrosis of renal parenchyma, the severity of these lesions was more in early stage of experiment and decrease in its severity with time along. . Intramuscular injection of amikacin in doses of 100 and 300 mg of amikacin /kg body weight per day caused significant decrease in glucose concenteration in serum with control group and before data from fifth to ninth day of experiment and glucosuria from fifth to seventh day of experiment in dose of 100 mg of amikacin /kg body weight per day (group A) while in dose of 300 mg of amikacin /kg body weight per day (group B) from fifth to ninth day of experiment . This might be attributed in the bases of lack of glomerular filteration through the glomeruli due to decreased tubular reabsorption of glucose after renal damage which manifested histopathologically by cloudy swelling and vacular degeneration of the lining epithelium of renal tubules in group A,while in group B the renal tubular damage manifested by thrombosis of some renal vessels with diffuse coagulative necrosis of renal parenchyma and the severity of the lesions was more in 1st day post the last injection and it was decreased with time. Also decrease of glucose in serum with glucoseuria might be attributed to hepatic alteration which manifested histopathologically by diffuse hydropic and vacuolar degeneration of hepatocytes at 1st day and 4th day post last injection in group A, while in group B it is manifested by thrombosis of some portal vessels with presence of multiple area of hepatic necrosis at 1st day post the last injection with hydropic and vacuolar degeneration.
Amikacin administration in a dose of 300 mg ∕kg.b.wt. Induced decrease in serum protein levels and proteinuria this might be attributed to progressive cellular and tubular dysfunction.
Intramuscular injection of amikacin in dose of 100 mg/kg body weight (group A) caused significant (with control group) decrease in calcium concentration in serum at the third day to ninth day while intramuscular injection of amikacin in dose of 300 mg/kg body weight caused significant (with control group) decrease in calcium concentration in serum from the first day to ninth day and significant (with before data) decrease in calcium concentration in serum at the fifth day to ninth day in both group ( A and B). While there is significant increase of calcium concentration in urine from third day to ninth day of experiment with control group after Intramuscular injection of amikacin in doses of 100 and 300 mg/kg body weight (group A and B) and significant increase in its concentration in urine with before data at fifth to ninth day after intramuscular injection of 300 mg of amikacin / kg.b.wt. This might be attributed to renal lesions which lead to failure of kidneys to reabsorption of calcium and help in excretion of calcium in urine especially in high dose of amikacin. Or might be the decrease in serum calcium level might be attributed to hypoproteinnemia where serum calcium concentration is decreased with decrease level of protein in serum because of the reduced amount of protein – bound calcium.
Serum sodium level was significantly with control group decrease after intramuscular injection of amikacin in dose of 300 mg/kg body weight ( group B) from fifth to seventh day of experiment while to ninth day with before data and urine sodium level was also significantly with control group and before data increased at the fifth day to seventh day of experiment .There is no significant change in serum and urine sodium concentration after intramuscular injection of amikacin in dose of 100 mg/kg body weight ( group A) .
Intramuscular injection of amikacin in dose of 100 mg/kg body weight ( group A) shown no significant (with control group and before data) in potassium concentration in serum and urine while serum potasium level was significantly with control group and before data increase after intramuscular injection of amikacin in dose of 300 mg/kg body weight ( group B) from fifth to ninth day of experiment and urine potasium level was also significantly with control group and before data decrease at the fifth day to ninth day of experiment .
Intramuscular injection of 100 and 300 mg of amikacin /kg body weight / day induce significant increase in AST and ALT concentrations which compared with control group and before data from fifth to seven day of experiment in AST and from third day to seven day of experiment in ALT in dose of 100 mg of amikacin /kg body weight per day (group A) while in doses of 300 mg of amikacin /kg body weight per day (group B) from third to ninth day of experiment in both parameter ,while there is no significant changes in both doses on ALP concentration was recorded.
Histopathologically hepatorenal degenerative changes were observed in group A, a long the experimental period; however, these changes were more sever during the early stage. Meanwhile, in group B, the recorded microscopical lesions in both liver and kidneys were more sever than these observed in group A particularly in the early stage in the early stage where thrombosis and necrosis with mononuclear cellular infiltration were observed in the examined liver and kidneys, with time, these histopathological changes became less severe and represented only by degeneration of the renal tubular epithelium and hepatocytes. Moreover, no detectable abnormal microscopic changes were found in the liver and kidney of rats in control group.
from the present results revealed that, amikacin can be used in case of enteritis , different diarrhea independent on dual action ( it can be used as antimicrobial and decrease intestinal movement ), post operative care of gastro-intestinal tract , early and mid-gestation but it is not preferable to be used in pre-partum , also the results revealed that amikacin has like antihistaminic action so it can be used in case of respiratory affection . Also amikacin can be used as a safe drug in case of hypertensive patient, it is not preferable in patient suffered from renal disorders and hepatic disorders so must be monitoring the patient which suffering from renal and hepatic affections . Also is not preferable in patient suffered from neuromuscular affection or lack of calcium, amikacin can be used in bacterial infection or feverable condition due to antipyretic analgesic activity.