the examples below describe the use of isolated cbd in combination with standard anti - epileptic drugs ( saeds ) in two different models of epilepsy , namely the ptz - induced seizure model and the pilocarpine - induced seizure model . the saeds used in these examples are ethosuximide , valproate and phenobarbital ( pilocarpine model only ). it is important to note that there are many different saeds available and the drugs chosen for these experiments provide a general overview of how the phytocannabinoid cbd is able to work in combination with different classes of drugs used in the treatment of epilepsy . the use of the phytocannabinoid cbd in combination with a standard anti - epileptic drug ( saed ) in the ptz - model of epilepsy male wistar rats ( p24 - 29 ; 75 - 110 g ) were used to assess the effects of the phytocannabinoid cbd in combination with saeds in the ptz model of generalised seizures . animals were habituated to the test environment , cages , injection protocol and handling prior to experimentation . animals were housed in a room at 21 ° c . on a 12 hour light : dark cycle ( lights on 0900 ) in 50 % humidity , with free access to food and water . the human dose equivalent ( hed ) can be estimated using the following formula : the k m for a rat is 6 and the k m for a human is 37 . thus , for a human of approx 60 kg a 100 mg / kg dose in rat would equate to a human dose of about 1000 mg . human doses of greater than 300 mg / day , through 400 mg / day in 100 mg intervals ( namely through 500 , 600 , 700 , 800 , 900 , 1000 , 1100 , 1200 , 1300 and 1400 mg ) to as much as 2000 mg / day are envisaged based on dose escalating studies with cbd ( example 2 ). five 6 l perspex tanks with lids were placed on a single bench with dividers between them . closed - circuit television ( cctv ) cameras were mounted onto the dividers to observe rat behaviour . sony topica ccd cameras ( bluecherry , usa ) were linked via bnc cables to a low - noise pc via brooktree digital capture cards ( bluecherry , usa ). zoneminder ( http :// www . zoneminder . com ) software was used to monitor rats , start and end recordings and manage video files . in - house linux scripts were used to encode video files into a suitable format for further offline analysis using the observer ( noldus technologies ). a range of doses of ptz ( 50 - 100 mg / kg body weight ) were used to determine the best dose for induction of seizures ( data not shown ). as a result , a dose of 80 mg / kg injected intra - peritoneally ( ip ; stock solution 50mg / ml in 0 . 9 % saline ) were used to screen the cbd / saeds combinations . on the day of testing , isolated cbd was administered via intra - peritoneal ( i . p .) injection at a dose of 100 mg / kg alongside animals that were injected with a matched volume of the cannabinoid vehicle ( 2 : 1 : 17 ethanol : cremophor : 0 . 9 % w / v nacl solution ), which served as the negative control group . animals were then observed for 1 hour , after which time they received an ip injection of 80 mg / kg ptz . negative vehicle controls were performed in parallel with cannabinoid - dosed subjects . after receiving a dose of ptz , animals were observed and videoed to determine the severity of seizure and latency to several seizure behaviour types ( see in vivo analysis , below ). animals were filmed for half an hour after last sign of seizure , and then returned to their cage . animals were observed during experimental procedures , but all analysis was performed offline on recorded video files using the observer behavioural analysis software ( noldus , netherlands ). a seizure severity scoring system was used to determine the levels of seizure experienced by subjects ( pohl & amp ; mares , 1987 ). all signs of seizure were detailed for all animals . table 1 . 1 seizure severity scoring scale , adapted from pohl & amp ; mares , 1987 . seizure righting score behavioural expression reflex 0 no changes to behaviour preserved 0 . 5 abnormal behaviour ( sniffing , excessive washing , preserved orientation ) 1 isolated myoclonic jerks preserved 2 atypical clonic seizure preserved 3 fully developed bilateral forelimb clonus preserved 3 . 5 forelimb clonus with tonic component and body preserved twist 4 tonic - clonic seizure with suppressed tonic phase lost 5 fully developed tonic - clonic seizure lost 6 death the latency ( in seconds ) from injection of ptz to first myoclonic jerk ( fmj ; score of 1 ), and to the animal attaining “ forelimb clonus with tonic component and body twist ” ( score of 3 . 5 ) were recorded . fmj is an indicator of the onset of seizure activity , whilst & gt ; 90 % of animals developed scores of 3 . 5 , and so is a good marker of the development of more severe seizures . data are presented as the mean ± s . e . m . within an experimental group . this is given as the median value for each experimental group based on the scoring scale below . the percentage of animals within an experimental group that died as a result of ptz - induced seizures . note that the majority of animals that developed tonic - clonic seizures ( scores of 4 and 5 ) died as a result , and that a score of 6 ( death ) automatically denotes that the animal also experienced tonic - clonic seizures . the time ( in seconds ) from the first sign of seizure ( typically fmj ) to either the last sign of seizure or , in the case of subjects that died , the time of death — separated into animals that survived and those that did not . this is given as the mean ± s . e . m . for each experimental group . for measures of latency and severity , one way analysis of variance ( anova ) was performed on the test groups to detect overall combinational effects of cbd and saeds ( p ≦ 0 . 05 considered significant ). significant anova results were followed by post hoc tests to test differences between vehicle and drug groups ( tukey &# 39 ; s test , p ≦ 0 . 05 considered significant ). from fig1 it can be seen that the addition of cbd to the saed valproate has an effect on reducing the percentage mortality and the incidence of tonic - clonic seizures . it is also shown that the combination of cbd and the higher dose of valproate is more effective at increasing the amount of time that the animal was seizure free . fig2 demonstrates that the combination of cbd and valproate was able to increase the latency to onset of seizure at all dose ranges , in addition it decreased the overall duration of the seizure . the data shown in fig3 demonstrates that the combination of cbd with the saed ethosuximide was also effective at reducing the severity and mortality of the seizures . it also at the higher dose of ethosuximide was able to increase the latency to onset of the seizures . the data demonstrated in this example clearly shows that the combination of cbd with a saed which has a mechanism of action involving sodium or calcium channels is of value when treating generalised seizures . the use of the phytocannabinoid cbd in combination with a standard anti - epileptic drug ( saed ) in the pilocarpine model of ( temporal lobe ) epilepsy isolated cbd was injected intra - peritoneally ( ip ) in the standard vehicle ( 1 : 1 : 18 ethanol : cremophor : 0 . 9 % w / v nacl ) at doses of 50 , 100 and 200 mg / kg alongside animals that received vehicle alone at a matched volume . 15 minutes later methylscopolamine ( 1 mg / kg ; to reduce peripheral muscarinic effects of pilocarpine ) was administered followed , 45 minutes later by pilocarpine ( 380 mg / kg , ip ) administration . fig4 demonstrates the anti - convulsant effects of a combination of cbd and valproate in the pilocarpine model of epilepsy . these data show that the combination of the cbd and valproate was able to increase the latency of onset of the seizure . it can be seen from the data illustrated in fig5 that in addition to increasing the latency of onset of the seizure the combination of cbd and valproate was able to decrease mortality and the percentage of tonic - clonic seizures . the table above clearly shows some of the advantages of using a combination of the two compounds . table 2 . 2 below describes the effect of using the phytocannabinoid cbd in combination with yet a further saed , phenobarbital , in the pilocarpine model of epilepsy . in contrast to the valproate combination data , this result demonstrate the selective nature of the combinations which is likely attributed to the different mechanisms of actions of these saed &# 39 ; s . the data demonstrated in the above examples shows that the combination of cbd with standard anti - epileptic drugs acting via sodium or calcium channels may be beneficial in the treatment of different types of epilepsy . this finding is of great significance to the many epilepsy sufferers whose condition is refractory to existing medication .