experimental animals : six intact , adult beagle dogs ( 3 males and 3 females ) that were 1 to 5 
 years of age [ 2.9  1.5 ( mean  standard deviation ) years old ] and that weighed 8.6 to 16.8 kg ( 11.5  3.2 kg ) 
 were used for three drug treatments with at least 10 days between each treatment . all dogs used in the present 
 study exhibited the ideal body condition ( body condition score 3/5 ) . each dog was received in the order of the i m treatment of a combination of alfaxalone - hpcd , medetomidine and 
 butorphanol ( mba ) , a combination of medetomidine and butorphanol ( mb ) , and alfaxalone - hpcd alone ( alfx ) . all 
 dogs were judged to be in good physical condition based upon a physical examination . food was withheld for 12 hr 
 before the each experiment , and water was continuously available . guide for the care and use of laboratory animals  prepared by rakuno gakuen university . the 
 animal care and use committee of rakuno gakuen university approved this study ( approved no . instrumentation : all dogs were instrumented with arterial and central venous catheters under 
 general anesthesia prior to the administration of each i m drug solution . anesthesia was induced by mask 
 induction using a vaporizer dial setting at 5% of sevoflurane ( sevoflo , ds pharma animal health co. , ltd . , once anesthetized , the dogs were orotracheally intubated , and anesthesia was 
 maintained with vaporizer dial setting at 3.03.5% of sevoflurane with oxygen . the dogs were placed in left 
 lateral recumbency for catheter instrumentation . in each dog , 22-gauge catheters ( supercath , medikit co. , ltd . , 
 tokyo , japan ) were placed into the left cephalic vein and the left dorsal pedal artery . in addition , an 18-gauge 
 catheter 30 cm in length ( intravascular catheter kit , medikit co. , ltd . ) was placed into the cranial vena cava 
 through the right jugular vein after the cervical catheter site was aseptically prepared and infiltrated with 1 
 mg / kg of 2% lidocaine ( 2% xylocaine astrazeneca , osaka , japan ) . the position of the tip and insertion length of 
 the central venous catheter were approximated and confirmed by pressure waveform . the dogs were infused with 
 lactated ringer s solution ( solulact , terumo co. , tokyo , japan ) at a rate of 10 ml / kg / hr 
 through the catheter placed into the cephalic vein during the sevoflurane anesthesia . after the completion of 
 catheter placements , the sevoflurane was discontinued , and each dog was extubated when their laryngeal reflex 
 was functional . each dog was then allowed to recover for 1 hr in a quiet room until the administration of its 
 allocated i m treatment . drug administration and data collection : following the 1 hr recovery period , the dogs received 
 i m alfaxalone - hpcd ( alfaxan , jurox pty . ltd . , rutherford , nsw , australia ) at 2.5 mg / kg ( alfx ) , medetomidine 
 ( domitor , nippon zenyaku kogyo co. , ltd . , fukushima , japan ) at 2.5 g / kg and butorphanol 
 ( vetorphal , meiji seika pharma co. , ltd . , tokyo , japan ) at 0.25 mg / kg ( mb ) , or alfaxalone - hpcd at 2.5 mg / kg , 
 medetomidine at 2.5 g / kg and butorphanol at 0.25 mg / kg ( mba ) in separate experiments . maddern 
 et al .   showed that the anesthetic induction dose 
 of iv alfaxalone - hpcd can be decreased to around one third by premedication with low dose of medetomidine and 
 butorphanol in dogs . therefore , the dose of i m alfaxalone - hpcd administration was set at 2.5 mg / kg ( one third of 
 anesthetic i m alfaxalone - hpcd dose ) in the present study . all i m drug solutions were administered to each dog at 
 total 0.3 ml / kg in volume under manual physical restraint . in the alfx and mb treatments , the 
 i m drug solution was prepared by mixing appropriate amounts of each product and diluting with normal saline 
 ( otsuka normal saline , otsuka pharmaceutical co. , ltd . , tokyo , japan ) up to 0.3 ml / kg volume in 
 a single syringe . in the mba treatment , the i m drug solution was prepared as a mixture of 0.1 
 ml of medetomidine ( 1 mg / ml ) , 2 ml of butorphanol ( 5 
 mg / ml ) and 10 ml of alfaxalone ( 10 mg / ml ) . thus , the final 
 dose of each drug given to the dogs was medetomidine 2.48 g / kg , butorphanol 0.248 mg / kg and 
 alfaxalone 2.48 mg / kg in the mba treatment . in each treatment , the i m drug solution was injected into the dorsal 
 lumbar muscle of the dog by using a syringe with a 23-gauge , 1-inch needle ( top injection needle , top co. , ltd . , the dogs breathed room air and were endotracheally intubated with an endotracheal tube 
 [ endotracheal tube with cuff ( i.d . 7.5 to 8.5 mm ) , fuji systems corp . , tokyo , japan ] when possible . anesthetic and cardiorespiratory 
 effects were evaluated in the dogs before each i m treatment ( baseline ) and at 2 , 5 , 10 , 15 , 20 , 30 , 45 , 60 , 90 
 and 120 min after the administration of each i m drug solution . evaluation of anesthetic effect : anesthetic effect was evaluated by the degree of 
 neuro - depression , the quality of anesthetic induction including the ease of endotracheal intubation and the 
 quality of recovery from anesthesia . the neuro - depression produced with each i m treatment was subjectively 
 evaluated by using an existing composite measurement scoring system in dogs . the scoring system consisted of 6 categories : spontaneous posture , placement on side , response to 
 noise , jaw relaxation , general attitude and nociceptive response to toe - pinch . these categories were rated with 
 a score of 0 to 2 for jaw relaxation , 0 to 3 for placement of side , general attitude and toe - pinch response and 
 0 to 4 for spontaneous posture and response to noise based on the responsiveness expressed by the dogs . total neuro - depressive score was calculated as the sum of the scores for 
 the 6 categories ( a maximum of 19 ) . the qualities of anesthetic induction and recovery were assessed using 
 numerical scoring systems previously used in dogs . a well - trained 
 observer ( n. h. ) was responsible for evaluation of the anesthetic effect of the treatments using these scoring 
 systems . in addition , we recorded the periods of time before the dogs lay down in lateral recumbency ( time until onset 
 of lateral recumbency ) , were intubated ( time until intubation ) , appeared the first spontaneous movement ( time 
 until spontaneous movement ) , and appeared their head lift ( time until head lift ) and unaided standing ( time 
 until unaided standing ) , after the start of each i m treatment . the durations of acceptance of endotracheal 
 intubation and maintenance of lateral recumbency were also recorded as the periods of time from the intubation 
 to extubation ( duration of intubation ) and from the onset of lateral recumbency to head lift ( duration of 
 lateral recumbency ) . measurements of cardiorespiratory valuables : lead ii electrocardiography ( ecg ) , heart rate 
 ( hr ; beats / min ) , respiratory rate ( rr ; breathes / min ) , rectal temperature ( rt;c ) , systolic arterial blood 
 pressure ( sabp ; mmhg ) , diastolic arterial blood pressure ( dabp ; mmhg ) , mean arterial blood pressure ( mabp ; mmhg ) 
 and central venous blood pressure ( cvp ; mmhg ) were recorded before and after the i m treatment . ecg , hr , rt , sabp , dabp , mabp and cvp were recorded by a patient monitoring system 
 ( ds-7210 , fukuda denshi co. , ltd . , sabp , dabp and mabp were directly measured by connecting the 
 catheter placed in the left pedal artery to a pressure transducer ( bd dtx plus dt-4812 , japan 
 becton , dickinson and co. , fukushima , japan ) . in addition , cvp was also measured by connecting the catheter 
 placed in the cranial vena cava to a pressure transducer . arterial blood samples ( 0.5 ml each ) were anaerobically withdrawn from the arterial catheters 
 into a heparinized syringe before and after the i m treatment . the blood samples were analyzed immediately after 
 collection to measure arterial ph ( pha ) , partial pressure of arterial oxygen ( pao2 ; mmhg ) and carbon 
 dioxide ( paco2 ; mmhg ) , and arterial plasma lactate concentration ( lac ; mmol / l ) using 
 a blood gas analyzer ( gem premier 3000 , instrumentation laboratory , tokyo , japan ) . in addition , arterial 
 bicarbonate concentration ( hco3 ; mmol / l ) , base excess ( b.e . ; the pha , 
 pao2 and paco2 were corrected for the rectal temperature determined immediately after 
 the blood collection . in the same way , central venous blood samples ( 0.5 ml each ) were 
 anaerobically withdrawn from the central venous catheters and immediately analyzed to obtain central venous 
 oxygen saturation ( scvo2;% ) using the blood gas analyzer . statistical analysis : the total neuro - depressive score was reported as the median  quartile 
 deviation and was analyzed by the friedman test to assess changes from baseline values with time for each 
 treatment . difference in the total neuro - depressive score and the qualities of anesthetic induction and recovery 
 amongst the treatments were compared by the friedman test with the scheff test for post hoc comparisons . the 
 times were compared by paired t test and one - way ( treatment ) factorial anova with the 
 bonferroni test for post hoc comparisons among treatments . the cardiorespiratory variables were analyzed using 
 two - way ( treatment and time ) repeated measure anova followed by the bonferroni test . observations and/or 
 perceived adverse effects related to drug administration were compared between treatments by using the chi 
 square test . the i m administration of each drug solution was accepted and completed without resisting it in all dogs under 
 manual physical restraint by one person . there was no swelling , redness or changes in the skin observed around 
 the injections sites of each dog after i m administration . immediately after each treatment , nausea like 
 behaviors , such as chewing and increased salivation , were observed in 2 dogs receiving the mb treatment and 3 
 dogs receiving the mba treatment ; however , the dogs did not exhibit vomiting in all treatment groups . anesthetic effects : the times associated with the anesthetic effect of each treatment are 
 shown in table 1table 1.times related to anesthetic effect after intramuscular ( i m ) treatments in dogsim treatmentsalfxmbmbatime until onset of lateral recumbency ( sec)224  110(n=6)850  563(n=4 ) 391  264(n=6)time until intubation ( min)12  4(n=5 ) 13(n=1 ) 16  6(n=6)time until spontaneous movement ( min)40  11(n=6)32  6(n=4 ) 79  22 ( n=6)time until head lift ( min)41  12(n=6)48  12(n=4 ) 89  25 ( n=6)time until unaided standing ( min)59  21(n=6)80  25(n=6)123  44 ( n=6)duration of intubation ( min)20(n=1 ) n / a(n=0 ) 60  24(n=5 ) duration of lateral recumbency ( min)46  13(n=6)48  28(n=4 ) 100  48(n=6)data are expressed as the mean  standard deviation . mb : medetomidine 2.5 g / kg and butorphanol 0.25 mg / kg co - administered 
 i m . mba : alfaxalone 2.5 mg / kg , medetomidine 2.5 g / kg and butorphanol 0.25 mg / kg 
 co - administered i m . we recorded the periods of time before the dogs lay down in lateral recumbency ( time 
 until onset of lateral recumbency ) , were intubated ( time until intubation ) , appeared the first spontaneous 
 movement ( time until spontaneous movement ) , and appeared their head lift ( time until head lift ) and 
 unaided standing ( time until unaided standing ) , after the start of each i m treatment . the durations of 
 acceptance of endotracheal intubation and maintenance of lateral recumbency were also recorded as the 
 periods of time from the intubation to extubation ( duration of intubation ) and from the onset of lateral 
 recumbency to head lift ( duration of lateral recumbency ) . b ) only 4 dogs became lateral recumbency and immobilized after the mb 
 treatment . c ) placement of the endotracheal tube was possible in 5 dogs in the alfx group and a dog in the 
 mb group . d ) endotracheal intubation was maintained a dog in the alfx group and 5 dogs in the mba 
 group .. all dogs became lateral recumbency quite rapidly after the alfx and mba treatments with mean 
 onset times of approximately 4 and 7 min , respectively . the times to lateral recumbency was longer and varied 
 more with the mb treatment . in addition , only 4 of 6 dogs went into lateral recumbency following the mb 
 treatment . there was no significant difference in the time of onset of lateral recumbency between the alfx and 
 mba treatments ( p=0.239 ) . the quality of anesthetic induction after i m treatments is shown in 
 table 2table 2.the qualities of anesthetic induction and recovery after intramuscular ( i m ) treatments in 
 dogsim treatmentsp value between treatmentsalfxmbmbainduction quality   score 1 : poor151p=0.130 score 2 : moderately smooth513 score 3 : quite smooth000 score 4 : very smooth 002recovery quality   score 1 : poor000p=0.747 score 2 : moderately smooth101 score 3 : quite smooth444 score 4 : very smooth 121data showed the number of dogs . mb : medetomidine 2.5 
 g / kg and butorphanol 0.25 mg / kg co - administered i m . mba : alfaxalone 2.5 mg / kg , 
 medetomidine 2.5 g / kg and butorphanol 0.25 mg / kg co - administered i m .. the quality of anesthetic induction score did not differ between treatments 
 ( p=0.130 ) . the dog scored as 1 ( poor ) after the mba treatment showed the same quality of 
 anesthetic induction ( score 1 ) after the mb and alfx treatments . endotracheal intubation was achieved in one , 5 
 and 6 dogs , and maintained in zero , one ( 17% ) and 5 dogs ( 83% ) administered the mb , alfx and mba treatments , 
 respectively . in the mba treatment group the times of first appearance of spontaneous movement , head lift and unaided 
 standing , and the duration of maintenance of lateral recumbency were considerably longer in the dogs receiving 
 the mba treatment compared with the dogs receiving the alfx treatment ( p=0.002 , 
 p=0.004 , p=0.010 and p=0.021 , respectively ) . mb : medetomidine 2.5 g / kg and butorphanol 0.25 mg / kg co - administered 
 i m . mba : alfaxalone 2.5 mg / kg , medetomidine 2.5 g / kg and butorphanol 0.25 mg / kg 
 co - administered i m . we recorded the periods of time before the dogs lay down in lateral recumbency ( time 
 until onset of lateral recumbency ) , were intubated ( time until intubation ) , appeared the first spontaneous 
 movement ( time until spontaneous movement ) , and appeared their head lift ( time until head lift ) and 
 unaided standing ( time until unaided standing ) , after the start of each i m treatment . the durations of 
 acceptance of endotracheal intubation and maintenance of lateral recumbency were also recorded as the 
 periods of time from the intubation to extubation ( duration of intubation ) and from the onset of lateral 
 recumbency to head lift ( duration of lateral recumbency ) . b ) only 4 dogs became lateral recumbency and immobilized after the mb 
 treatment . c ) placement of the endotracheal tube was possible in 5 dogs in the alfx group and a dog in the 
 mb group . d ) endotracheal intubation was maintained a dog in the alfx group and 5 dogs in the mba 
 group . mb : medetomidine 2.5 
 g / kg and butorphanol 0.25 mg / kg co - administered i m . mba : alfaxalone 2.5 mg / kg , 
 medetomidine 2.5 g / kg and butorphanol 0.25 mg / kg co - administered i m . 1.median (  quartile deviation ) total neuro - depressive scores in 6 dogs before ( baseline ) and after the 
 intramuscular ( the categories of a 
 composite measure scoring system were rated in scores 0 to 2 for jaw relaxation , 0 to 3 for placement of 
 side , general attitude and toe - pinch response , or 0 to 4 for spontaneous posture and response to noise 
 . total neuro - depressive score was calculated as a sum of 
 scores in these 6 categories . mb : medetomidine 2.5 
 g / kg and butorphanol 0.25 mg / kg coadministered i m . mba : alfaxalone 2.5 mg / kg , 
 medetomidine 2.5 g / kg and butorphanol 0.25 mg / kg coadministered i m . significant difference from the mb group 
 ( p<0.05 ) .. the median total neuro - depressive scores peaked at 10 to 20 min after the alfx treatment ( median total 
 neuro - depressive score 15.0 ) , at 30 to 45 min after the mb treatment ( median total neuro - depressive score 12.5 ) 
 and at 10 to 30 min after the mba treatment ( median total neuro - depressive score 17.0 ) . no dogs showed the 
 maximum score of 19 , because toe - pinch responses could still be elicited in all dogs . the total neuro - depressive 
 score after the mba treatment was significantly higher than those after the alfx and mb treatments 
 ( p<0.001 , each ) . median (  quartile deviation ) total neuro - depressive scores in 6 dogs before ( baseline ) and after the 
 intramuscular ( i m ) treatments . based on responsiveness expressed by the dogs , the categories of a 
 composite measure scoring system were rated in scores 0 to 2 for jaw relaxation , 0 to 3 for placement of 
 side , general attitude and toe - pinch response , or 0 to 4 for spontaneous posture and response to noise 
 . total neuro - depressive score was calculated as a sum of 
 scores in these 6 categories . mb : medetomidine 2.5 
 g / kg and butorphanol 0.25 mg / kg coadministered i m . mba : alfaxalone 2.5 mg / kg , 
 medetomidine 2.5 g / kg and butorphanol 0.25 mg / kg coadministered i m . the quality of recovery score did not differ between treatments ( p=0.747 ) . during the recovery 
 period , ataxia was observed in 2 dogs ( 33% ) , one dog ( 17% ) and 3 dogs ( 50% ) receiving the alfx , mb and mba 
 treatments , respectively . transient muscular tremors or twitching was observed in 2 dogs ( 33% ) , 2 dogs ( 33% ) and 
 5 dogs ( 83% ) receiving the alfx , mb and mba treatments , respectively . pronounced limb extension was also 
 observed in one dog ( 17% ) receiving the alfx treatment , and vocalization or struggling was observed in one dog 
 ( 17% ) each administered the alfx , mb and mba treatments . changes in cardiorespiratory valuables : changes in cardiorespiratory variables are summarized 
 in table 3table 3.cardiorespiratory variables before and after each intramuscular ( i m ) treatment in dogsminutes after each i m treatmentsbaseline2510152030456090120rt ( c)alfx37.6  0.237.7  0.237.6  0.337.5  0.437.4  0.437.4  0.437.3  0.437.3  0.437.4  0.437.6  0.637.6  0.5mb37.9  0.637.9  0.337.9  0.337.9  0.437.8  0.437.7  0.437.5  0.537.4  0.637.3  0.637.5  0.437.5  0.4mba38.0 0.437.8  0.337.8  0.337.7  0.237.6  0.237.5  0.237.3  0.237.1  0.236.8  0.336.6  0.736.9  1.1hr ( beats / min)alfx99  18102  1899  21119  12121  10118  15103  1798  33101  4491  2479  21mb108  282  1371  1766  1065  1862  1362  1466  1762  1869  2166  11mba104  1997  5161  1363  1560  1364  1558  1760  1864  1475  2377  16rr ( breaths / min)alfx29  533  1128  828  1025  1321  620  424  826  1729  2122  5mb46  4617  415  314  414  415  312  312  211  312  313  2mba36  822  622  521  418  616  514  315  515  414  514  3sabp ( mmhg)alfx186  24170  27166  24160  21151  22158  18156  19160  21165  28171  23159  37mb192  28192  18179  20167  24162  20155  19151  18149  16145  17158  19166  20mba186  15176  17183  21159  26153  14149  12148  12145  9139  13135  10154  29mabp ( mmhg)alfx108  1499  1596  11100  1197  1399  1497  1098  1397  11101  14102  21mb118  18120  13105  1399  1398  1592  987  1185  787  899  1099  7mba111  8117  20112  23100  1999  1694  1388  886  1186  890  1396  16dabp ( mmhg)alfx82  1075 1073  879  1077  978  1476  877  1276  872  872  11mb89  1392  1078  976  977  1270  667  965  568  776  775  7mba81  389  1687  2177  1677  1470  1068  866  1165  769  1275  14cvp ( mmhg)alfx2  22  12  13  21  12  02  12  13  13  13  1mb3  23  25 45  25  26  24  24  24  14  24  2mba4  63  16  26  16  26  25  15  14  15  25  2phaalfx7.39  0.027.37  0.027.37  0.027.38  0.027.37  0.027.37  0.017.36  0.027.37  0.027.38  0.037.38  0.027.39  0.02mb7.39  0.027.39  0.037.37  0.047.35  0.027.35  0.027.35  0.027.34  0.027.36  0.027.37  0.027.37  0.027.38  0.03mba7.38  0.017.36  0.027.35  0.027.34  0.017.33  0.017.33  0.017.34  0.017.35  0.017.35  0.027.36  0.027.35  0.02pao2 ( mmhg)alfx95  889  692  891  1388  1088  1291  896  1098  899  1298  7mb101  895  593  693  793  896  1289  692  492  596  696  4mba100  892  688  689  890  791  590  690  588  788  1087  4paco2 ( mmhg)alfx39  440  440  439  540  541  341  440  539  438  436  4mb39  239  240  343  343  343  343  342  242  341  241  3mba39  341  242  243  343  242  343  443  343  343  344  2hco3 ( mmol / l)alfx23.5  3.223.4  2.722.9  2.623.1  3.023.2  2.923.5  2.623.1  3.123.0  3.122.9  3.122.4  2.321.9  3.0mb23.6 1.223.6  1.623.7  1.423.7  1.723.3  1.023.8  1.0mba23.8  1.923.1  1.823.1  1.822.9  1.922.5  1.822.3  1.822.8  1.823.3  1.423.7  1.324.3  1.324.5  1.2b.e . ( mmol / l)alfx1.1  2.91.5  2.42.0  2.31.7  2.41.7  2.51.7  2.52.1  2.82.0  2.72.0  3.02.1  2.22.4  2.7mb0.9  1.21.4  1.32.1  1.42.1  1.22.1  1.22.2  1.02.1  1.41.6  1.41.6  1.71.8  1.01.2  1.5mba0.9  1.72.0  1.92.2  1.82.7  1.83.2  1.83.3  1.62.8  1.52.3  1.12.1  1.11.4  1.31.3  1.3sao2 ( % ) alfx97  196  197  197  296  196  296  197  197  197  197  1mb97  197  096  196  196  197  196  197  197  197  197  1mba97  196  196  196  196  196  096  196  196  196  296  0scvo2 ( % ) alfx74  676  683  485  284  582  983  481  878  873  672  5mb78  866  1065  569  470  773  476  677  478  566  672  5mba76  970  568  667  674  772  772  769  771  968  1173  10lac ( mmol / l)alfx1.2  0.41.0  0.31.0  0.31.0  0.31.0  0.31.1  0.31.0  0.30.7  0.20.7  0.20.7  0.40.7  0.3mb1.7  0.71.5  0.61.5  0.51.5  0.41.5  0.41.3  0.31.1  0.30.9  0.31.0  0.21.0  0.21.0  0.2mba1.2  0.41.2  0.31.2  0.41.3  0.31.2  0.41.1  0.31.0  0.30.9  0.30.8  0.30.8  0.20.8 rt : rectal tempareture , hr : heart rate , rr : respiratory 
 rate , sabp : systolic arterial blood pressure , mabp : mean arterial blood pressure , dabp : diastolic arterial 
 blood pressure , cvp : central venous pressure , pha : arterial ph , pao2 : partial pressure of 
 arterial oxygen , paco2 : partial pressure of arterial carbon dioxide , hco3 : arterial 
 bicarbonate concentration , b.e . : arterial base excess , sao2 : arterial oxygen saturation , 
 scvo2 : central venous oxygen saturation , lac : arterial plasma lactate concentration . mb : medetomidine 2.5 g / kg and butorphanol 0.25 
 mg / kg coadministered i m . mba : alfaxalone 2.5 mg / kg , medetomidine 2.5 g / kg and 
 butorphanol 0.25 mg / kg coadministered i m . c ) significant difference from the mb group 
 ( p<0.05 ) .. the rts after the mba treatment gradually decreased from baseline ( p<0.001 ) . clinically relevant bradycardia ( hr < 60 beats / min ) was observed in 4 dogs ( 67% ) each receiving the mb and mba 
 treatments . the hrs after the mb and mba treatments were significantly lower than those after the alfx treatment 
 ( p<0.001 , each ) . there were no significant differences for the sabp , dabp and mabp between 
 the i m treatment groups , and clinically relevant hypotension ( mabp < 60 mmhg ) was not 
 observed during the present study . the cvps after the mb and mba treatments were significant higher than those 
 after the alfx treatment ( p<0.001 , each ) . the rr decreased from baseline after the mb and 
 mba treatments ( p<0.001 and p=0.026 ) and were also significantly lower than 
 that in the alfx treatment . the paco2 was maintained within normal range , although statistical 
 differences were detected in the mb and mba treatments compared with alfx treatment ( p=0.006 
 and p<0.001 ) . spontaneous breathing was maintained , and clinical relevant hypoxemia 
 ( pao2 < 60 mmhg or sao2 < 90% ) was not detected in all treatment groups . the pha 
 after the mb and mba treatments was significantly lower compared to the alfx treatment ( p=0.002 
 and p<0.001 ) . the scvo2 after the mb and mba treatments was lower compared to the 
 alfx treatment ( p<0.001 , each ) . lac after each treatment were 
 maintained between the reference ranges for dogs [ 10 , 11 ] . rt : rectal tempareture , hr : heart rate , rr : respiratory 
 rate , sabp : systolic arterial blood pressure , mabp : mean arterial blood pressure , dabp : diastolic arterial 
 blood pressure , cvp : central venous pressure , pha : arterial ph , pao2 : partial pressure of 
 arterial oxygen , paco2 : partial pressure of arterial carbon dioxide , hco3 : arterial 
 bicarbonate concentration , b.e . : arterial base excess , sao2 : arterial oxygen saturation , 
 scvo2 : central venous oxygen saturation , lac : arterial plasma lactate concentration . mb : medetomidine 2.5 g / kg and butorphanol 0.25 
 mg / kg coadministered i m . mba : alfaxalone 2.5 mg / kg , medetomidine 2.5 g / kg and 
 butorphanol 0.25 mg / kg coadministered i m . in the present study , the simultaneous ( i.e. mixed in the same syringe ) i m administration of alfaxalone - hpcd 
 ( 2.5 mg / kg ) , medetomidine ( 2.5 g / kg ) and butorphanol ( 0.25 mg / kg ) provided an anesthetic 
 effect allowing the endotracheal intubation without severe cardiorespiratory depression in healthy dogs . medetomidine induces marked peripheral vasoconstriction and cardiovascular depression when administered its 
 recommended label dose ( 20 g / kg iv or 40 g / kg i m ) in dogs [ 22 , 27 ] . reported that lower doses of medetomidine ( 1 and 2 
 g / kg iv ) produced less cardiovascular depression in dogs . on the other hand , low doses of 
 medetomidine ( 2 or 5 butorphanol ( 0.25 mg / kg i m ) provides moderate analgesia with minimum 
 sedation for only 2 to 3 hr based on its rapid clearance [ 15 , 21 ] . girard et al . 
 reported that the combination of low dose medetomidine and butorphanol produced synergic sedative effects . it 
 was reported that the anesthetic induction doses of iv alfaxalone - hpcd were 0.8  0.3 mg / kg in dogs premedicated 
 with medetomidine ( 4 g / kg i m ) and butorphanol ( 0.1 mg / kg i m )   and 2.6  0.4 mg / kg in unpremedicated dogs . recently , 
 we reported that the i m doses of alfaxalone - hpcd alone at 7.5 mg / kg or 10 mg / kg provided reliable induction of 
 anesthesia in dogs . as we expected , the anesthetic induction dose of 
 i m alfaxalone - hpcd could be reduced by the co - administration of low dose of medetomidine and butorphanol . 
 according to the guideline by the european federation of pharmaceutical industries associations and the european 
 centre for the validation of alternative methods , the i m volume considered as good practice is 0.25 
 ml / kg , and the maximal dose volume is 0.5 ml / kg in dogs . the i m volume of the mba treatment was 0.3 ml / kg and was 
 accepted and completed without resisting it in all dogs under manual physical restraint . in addition , no 
 pathological changes around the injection sites were observed after the mba treatment . our result suggests that 
 the i m administration of alfaxalone - hpcd at 2.5 mg / kg combined with medetomidine at 2.5 g / kg 
 and butorphanol at 0.25 mg / kg can produce anesthetic effects allowing endotracheal intubation with a humane and 
 clinically acceptable injection volume for dogs . in the present study , the mba treatment showed a larger variation of the time of onset of lateral recumbency 
 than the alfx treatment . in addition , the mba treatment was slightly slower in onset of anesthesia compared with 
 the alfx treatment , although statistical analysis could not be performed . we reported that an i m administration 
 of alfaxalone - hpcd alone at 7.5 mg / kg and 10 mg / kg produced anesthetic effects in dogs enabling to intubate at 8 
  1 min and 10  2 min , respectively . the endotracheal intubation 
 was achieved at 16  6 min after the mba treatment in the present study . from these findings , the mba treatment 
 seemed to be slightly slower in onset of anesthesia compared with those after i m alfaxalone - hpcd alone . it is 
 possible that the 2-adrenoceptors agonists ( e.g. dexmedetomidine which is the s - enantiomer of 
 medetomidine ) interfere with the absorption of the co - administered drug via vasoconstriction around the site of 
 injection . it was supposed that vasoconstriction produced by 
 medetomidine might interfere with the absorption of alfaxalone - hpcd and resulted in slower onset of anesthetic 
 effect with large variation of onset time in dogs receiving the mba treatment . muir et al .   reported that an iv administration of 
 alfaxalone - hpcd alone resulted in dose - dependent changes in cardiovascular and respiratory parameters in dogs 
 breathing room air . an iv administration of alfaxalone - hpcd alone at 6 mg / kg produced hypoxia associated with 
 hypoventilation mainly caused by a decrease in respiratory rate and transient apnea , although the cardiovascular 
 status was well maintained . hypoxemia associated with a decrease in 
 rr was observed in a dose - dependent manner following the i m administration of alfaxalone - hpcd alone at 5 , 7.5 
 and 10 mg / kg , while the cardiovascular status was well maintained . 
 in the present study , the rr decreased significantly from the baseline value after each i m treatment , but the rr 
 and paco2 were maintained between the normal range for dogs under general anesthesia , and clinical relevant hypoxemia was not detected in any dog breathing 
 room air . kuo et al .   reported that iv 
 administration of medetomidine at 20 g / kg and butorphanol at 0.2 mg / kg caused a marked 
 decrease in rr and mild hypoventilation without hypoxemia in dogs . therefore , we considered that the decreased 
 rr observed after the mb and mba treatments was mainly due to the central nervous system depression produced by 
 both 2-adrenoceptor   and opiate receptor ligand binding 
 . in conclusion , the simultaneous i m administration of 
 alfaxalone - hpcd ( 2.5 mg / kg ) , medetomidine ( 2.5 g / kg ) and butorphanol ( 0.25 mg / kg ) produced an 
 anesthetic effect with a mild respiratory depression in healthy dogs . in the present study , clinically relevant bradycardia was observed in some dogs receiving the mb or mba 
 treatment , although clinically relevant hypotension ( mabp < 60 mmhg ) was not observed in any dog . the cvps 
 after the mb or mba treatment were significant higher than that after the alfx treatment . reported that medetomidine induced a dose - dependent 
 cardiovascular depression including a transient hypertension , baroreceptor mediated bradycardia and decreased 
 cardiac output followed by an initial peripheral vasoconstriction . in addition , kuo et al . 
  reported that the sedation with medetomidine and butorphanol had 
 similar cardiovascular effects to that of medetomidine alone . thus , decreases in hr after the mb and mba 
 treatments were most likely caused by a baroreceptor mediated reflex response associated with the administration 
 of medetomidine [ 13 , 22 ] . 
 increases in cvp after the mb and mba treatments may also be related to a decrease in venous capacitance and 
 cardiac output mainly associated with the administration of medetomidine . in the present study , the scvo2 after the mb and mba treatments was lower than that 
 after the alfx treatment . decreased scvo2 is commonly associated with increased tissue oxygen demand , 
 decreased oxygen delivery or both . tissue oxygen demand in 
 anesthetized or sleeping dogs is generally lower than that in awake dogs . on the other hand , oxygen delivery decreases when cardiac output decreases , blood hemoglobin 
 content can decrease ( i.e. bleeding ) , or hypoxemia occurs . in the present study , therefore , we surmised that the lower scvo2 after the mb and mba 
 treatments also reflected the decreased cardiac output followed by vasoconstriction produced by medetomidine . 
 however , the fact that the arterial blood pressure , hco3 , b.e . and lac remained within clinically 
 acceptable ranges indicated that the tissue of our dogs received adequate oxygen throughout the anesthetic 
 period . from these findings , the simultaneous i m administration of alfaxalone - hpcd ( 2.5 mg / kg ) , medetomidine 
 ( 2.5 g / kg ) and butorphanol ( 0.25 mg / kg ) provides anesthetic effect without severe 
 cardiovascular depression in healthy dogs nevertheless , the mba treatment is not recommended for dogs with 
 significant cardiac disease , because it may cause a decrease in cardiac output followed by marked 
 vasoconstriction induced by medetomidine . in our previous study using the same recovery score used in the present study , the recovery scores were judged 
 as score 2 ( moderately smooth ) in all 6 dogs receiving i m alfaxalone - hpcd alone at 5 , 7.5 and 10 mg / kg . all dogs ( 100% ) receiving i m alfaxalone - hpcd alone at 5 , 7.5 and 10 
 mg / kg showed involuntary muscle tremors and a transient staggering gait . in addition , pronounced limb extension was also observed in 4 dogs ( 67% ) , 3 dogs ( 50% ) and 5 dogs 
 ( 83% ) , and a transient paddling of the forelimbs was observed in 3 dogs ( 50% ) , 2 dogs ( 33% ) and 3 dogs ( 50% ) 
 receiving the alfaxalone - hpcd alone at 5 , 7.5 and 10 mg / kg , respectively . the quality of recovery from the mba treatment seemed to be better with less undesirable events , 
 compared with that from the i m alfaxalone - hpcd alone . it was 
 reported that premedication with buprenorphine and acepromazine   or 
 co - administration of dexmedetomidine   improved the quality of 
 recovery from total intravenous anesthesia with alfaxalone - hpcd in dogs . these findings indicate that 
 premedication or co - administration of sedative and analgesic drugs may improve the quality of recovery from 
 alfaxalone - hpcd anesthesia . it may be concluded that the simultaneous i m administration of alfaxalone - hpcd ( 2.5 
 mg / kg ) , medetomidine ( 2.5 g / kg ) and butorphanol ( 0.25 mg / kg ) provided a good anesthesia with 
 better quality of recovery . we surmise that the dose sparing effect on the anesthetic i m alfaxalone - hpcd by use 
 of a combination of medetomidine and butorphanol may be related to less undesirable events during recovery . however , the frequency of muscle tremors or twitching during recovery from the mba treatment ( 83% ) was higher 
 compared with the mb ( 33% ) and alfx treatments ( 33% ) . the higher frequency of muscular tremors or twitching during the recovery from the mba treatment 
 may be associated with both alfaxalone - hpcd and co - administered drugs ( medetomidine and/or butorphanol ) . a 
 further study will be necessary to determine the influence of simultaneously administered drugs on the quality 
 of recovery from the i m alfaxalone - hpcd in dogs . vomiting is a well - known side effect of medetomidine in dogs . in 
 the present study , no dogs vomited , although nausea like behavior was observed in dogs receiving the mb and mba 
 treatments , respectively . it has been reported that butorphanol produced central antiemetic properties through 
 the opioid receptor and effectively reduced vomiting induced by cisplatin   and medetomidine . although the mechanism of the 
 interaction was not clear , we speculate that the co - administeration of butorphanol might prevent 
 medetomidine - induced vomiting . in the present study , the dogs showed deep sedation within 224  110 sec and had laid in lateral recumbency for 
 46  13 min after the i m treatment of alfaxalone - hpcd alone at 2.5 mg / kg . in addition , the alfx treatment did 
 not cause any cardiorespiratory depression in the dogs . we consider that the alfx treatment may provide enough 
 sedation and immobilization to complete less invasive procedures , such as securing vascular access or diagnostic 
 imaging examination . however , there are some limitations when attempting to generalize the results of the 
 present study to clinical practice because of the minimum sample size with the large distribution of age and 
 body weight in the experimental animals used in the present study . in addition , all the animals were 
 anesthetized with sevoflurane in oxygen for the catheter instrumentation before the each i m treatment . we can not 
 rule out the influence of the proceeded sevoflurane anesthesia on the anesthetic and cardiorespiratory effects 
 of each i m treatment and the quality of recovery from each i m treatment . other limitation of the present study 
 is that plasma biochemistry was not performed before each treatment although there were no clinical symptoms of 
 hypoactivitiy , anorexia , vomiting , diarrhea and anemia in any of the dogs . in addition , it might be better to 
 assess the neuro - depressive score by two observers . we are also concerned that mixing the drugs in the same 
 syringe might affect each component . chemical reactions including turbidity , precipitation or color changes were 
 not observed before each administration in the present study . in conclusion , the i m administration of alfaxalone - hpcd at 2.5 mg / kg combined with medetomidine at 2.5 
 g / kg and butorphanol at 0.25 mg / kg produced adequate anesthesia allowing endotracheal 
 intubation without severe cardiorespiratory depression in healthy dogs .
the pharmacological effects of intramuscular ( i m ) administration of alfaxalone combined with medetomidine and 
 butorphanol were evaluated in 6 healthy beagle dogs . 
 each dog received three treatments with a minimum 10-day 
 interval between treatments . 
 the dogs received an i m injection of alfaxalone 2.5 mg / kg ( alfx ) , medetomidine 
 2.5 g / kg and butorphanol 0.25 mg / kg ( mb ) , or their combination ( mba ) 1 hr after the recovery 
 from their instrumentation . 
 endotracheal intubation was attempted , and dogs were allowed to breath room air . 
 neuro - depressive effects ( behavior changes and subjective scores ) and cardiorespiratory parameters ( rectal 
 temperature , heart rate , respiratory rate , direct blood pressure , central venous pressure and blood gases ) 
 were evaluated before and at 2 to 120 min after i m treatment . 
 each dog became lateral recumbency , except for 
 two dogs administered the mb treatment . 
 the duration was longer in the mba treatment compared with the alfx 
 treatment ( 100  48 min vs 46  13 min ) . 
 maintenance of the endotracheal tube lasted for 60  24 min in five 
 dogs administered the mba treatment and for 20 min in one dog administered the alfx treatment . 
 cardiorespiratory variables were maintained within clinically acceptable ranges , although decreases in heart 
 and respiratory rates , and increases in central venous pressure occurred after the mba and mb treatments . 
 the 
 mba treatment provided an anesthetic effect that permitted endotracheal intubation without severe 
 cardiorespiratory depression in healthy dogs .