Levetiracetam is a highly soluble and permeable compound. Levetiracetam is rapidly absorbed after oral administration with a close to complete absolute bioavailability.
The pharmacokinetics and bioequivalence of Desitrend 1000 mg coated granules in sachet and Desitrend 1500 mg coated granules in sachet were investigated in two studies in healthy volunteer subjects. In a first study, Desitrend 1000 mg coated granules in sachet was compared with film-coated reference tablets containing 1000 mg Levetiracetam. In a second study, Desitrend 1500 mg coated granules in sachet was compared with two film-coated reference tablets containing 750 mg Levetiracetam. Both studies were carried out in 16 healthy volunteers (each time eight females and eight males) according to an open-label, controlled crossover design with randomly assigned sequences. Each subject was studied on two occasions at least one week apart for washout purposes. Based on the plasma pharmacokinetics of Levetiracetam after the oral administration of Desitrend 1000 mg coated granules in sachet and Desitrend 1500 mg coated granules in sachet, Desitrend coated granules in sachet were evidenced to be bioequivalent with the reference film-coated tablets (Table 4).
The time courses of the plasma concentrations were almost superimposable (Figure 1). Desitrend 1000 mg coated granules in sachet were bioequivalent with the film-coated reference tablets with regard to the maximum exposure (Cmax) and total exposure (AUC) to Levetiracetam: the 90% confidence intervals of the ratios for test to reference were 90 to 113% and 97 to 106%, respectively. Desitrend 1500 mg coated granules in sachet were bioequivalent with the film-coated reference tablets with regard to the maximum exposure (Cmax) and total exposure (AUC) to Levetiracetam: the 90% confidence intervals of the ratios for test to reference were 89 to103 % and 97 to 104%, respectively. There were no relevant differences with regard to the time to reach Cmax (tmax) and the half-life (t½).
Table 4: Mean values of the pharmacokinetics of Levetiracetam after single oral doses of 1000 mg and 1500 mg Desitrend coated granules in sachet and the reference film-coated tablets
| | | Single doses of 1000 mg Levetiracteam | Single doses of 1500 mg Levetiracteam |
| | | Desitrend coated granules in sachet | Film-coated reference tablets | Desitrend coated granules in sachet | Film-coated reference tablets |
| Cmax | μg/ml | 42.0 | 41.7 | 64.6 | 67.3 |
| tmax | min | 35 | 40 | 35 | 35 |
| AUC(0-tz) | μg.h/ml | 264.7 | 262.2 | 450.6 | 448.4 |
| AUC(0-∞) | μg.h/ml | 271.7 | 268.4 | 461.4 | 458.8 |
| t½ | h | 6.90 | 6.58 | 6.65 | 6.61 |
Legend: geometric mean of Cmax, AUC(0-tz), and AUC(0-∞), arithmetic mean of t½ and median of tmax for single oral doses of 1000 (first study) and 1500 mg Levetiracetam (second study) by means of Desitrend coated granules in sachet and the reference film-coated tablets
Figure 1: Time courses of the geometric mean plasma concentrations of Levetiracetam after single oral doses of 1000 mg and 1500 mg Desitrend coated granules in sachet and the reference film-coated tablets
Legend: time courses of the geometric mean plasma concentrations of Levetiracetam after single oral doses of 1000 (first study: left panel) and 1500 mg Levetiracetam (second study: right panel) by means of Desitrend coated granules in sachet (●) and film-coated reference tablets (○).
The pharmacokinetic profile is linear with low intra- and inter-subject variability. There is no modification of the clearance after repeated administration. There is no evidence for any relevant gender, race or circadian variability. The pharmacokinetic profile is comparable in healthy volunteers and in patients with epilepsy.
Due to its complete and linear absorption, plasma levels can be predicted from the oral dose of levetiracetam expressed as mg/kg bodyweight. Therefore there is no need for plasma level monitoring of levetiracetam.
A significant correlation between saliva and plasma concentrations has been shown in adults and children (ratio of saliva/plasma concentrations ranged from 1 to 1.7 for oral tablet formulation and after 4 hours post-dose for oral solution formulation).
Adults and adolescents
Absorption
Levetiracetam is rapidly absorbed after oral administration. Oral absolute bioavailability is close to 100 %. Peak plasma concentrations (Cmax) are achieved at 1.3 hours after dosing. Steady-state is achieved after two days of a twice daily administration schedule. Peak concentrations (Cmax) are typically 31 and 43 μg/ml following a single 1,000 mg dose and repeated 1,000 mg twice daily dose, respectively. The extent of absorption is dose-independent and is not altered by food.
Distribution
No tissue distribution data are available in humans.
Neither levetiracetam nor its primary metabolite are significantly bound to plasma proteins (< 10 %).
The volume of distribution of levetiracetam is approximately 0.5 to 0.7 l/kg, a value close to the total body water volume.
Biotransformation
Levetiracetam is not extensively metabolised in humans. The major metabolic pathway (24 % of the dose) is an enzymatic hydrolysis of the acetamide group. Production of the primary metabolite, ucb L057, is not supported by liver cytochrome P450 isoforms. Hydrolysis of the acetamide group was measurable in a large number of tissues including blood cells. The metabolite ucb L057 is pharmacologically inactive.
Two minor metabolites were also identified. One was obtained by hydroxylation of the pyrrolidone ring (1.6 % of the dose) and the other one by opening of the pyrrolidone ring (0.9 % of the dose). Other unidentified components accounted only for 0.6 % of the dose.
No enantiomeric interconversion was evidenced in vivo for either levetiracetam or its primary metabolite.
In vitro, levetiracetam and its primary metabolite have been shown not to inhibit the major human liver cytochrome P450 isoforms (CYP3A4, 2A6, 2C9, 2C19, 2D6, 2E1 and 1A2), glucuronyl transferase (UGT1A1 AND UGT1A6) and epoxide hydroxylase activities. In addition, levetiracetam does not affect the in vitro glucuronidation of valproic acid.
In human hepatocytes in culture, levetiracetam had little or no effect on CYP1A2, SULT1E1 or UGT1A1. Levetiracetam caused mild induction of CYP2B6 and CYP3A4. The in vitro data and in vivo interaction data on oral contraceptives, digoxin and warfarin indicate that no significant enzyme induction is expected in vivo. Therefore, the interaction of Desitrend with other substances, or vice versa, is unlikely.
Elimination
The plasma half-life in adults was 7±1 hours and did not vary either with dose, route of administration or repeated administration. The mean total body clearance was 0.96 ml/min/kg.
The major route of excretion was via urine, accounting for a mean 95 % of the dose (approximately 93 % of the dose was excreted within 48 hours). Excretion via faeces accounted for only 0.3 % of the dose.
The cumulative urinary excretion of levetiracetam and its primary metabolite accounted for 66 % and 24 % of the dose, respectively during the first 48 hours.
The renal clearance of levetiracetam and ucb L057 is 0.6 and 4.2 ml/min/kg respectively indicating that levetiracetam is excreted by glomerular filtration with subsequent tubular reabsorption and that the primary metabolite is also excreted by active tubular secretion in addition to glomerular filtration. Levetiracetam elimination is correlated to creatinine clearance.
Elderly
In the elderly, the half-life is increased by about 40 % (10 to 11 hours). This is related to the decrease in renal function in this population (see section 4.2).
Renal impairment
The apparent body clearance of both levetiracetam and of its primary metabolite is correlated to the creatinine clearance. It is therefore recommended to adjust the maintenance daily dose of Desitrend, based on creatinine clearance in patients with moderate and severe renal impairment (see section 4.2).
In anuric end-stage renal disease adult subjects the half-life was approximately 25 and 3.1 hours during interdialytic and intradialytic periods, respectively.
The fractional removal of levetiracetam was 51 % during a typical 4-hour dialysis session.
Hepatic impairment
In subjects with mild and moderate hepatic impairment, there was no relevant modification of the clearance of levetiracetam. In most subjects with severe hepatic impairment, the clearance of levetiracetam was reduced by more than 50 % due to a concomitant renal impairment (see section 4.2).
Paediatric population
Children (4 to 12 years)
Following single oral dose administration (20 mg/kg) to epileptic children (6 to 12 years), the half-life of levetiracetam was 6.0 hours. The apparent body weight adjusted clearance was approximately 30 % higher than in epileptic adults.
Following repeated oral dose administration (20 to 60 mg/kg/day) to epileptic children (4 to 12 years), levetiracetam was rapidly absorbed. Peak plasma concentration was observed 0.5 to 1.0 hour after dosing. Linear and dose proportional increases were observed for peak plasma concentrations and area under the curve. The elimination half-life was approximately 5 hours. The apparent body clearance was 1.1 ml/min/kg.
Infants and children (1 month to 4 years)
Following single dose administration (20 mg/kg) of a 100 mg/ml oral solution to epileptic children (1 month to 4 years), levetiracetam was rapidly absorbed and peak plasma concentrations were observed approximately 1 hour after dosing. The pharmacokinetic results indicated that half-life was shorter (5.3 h) than for adults (7.2 h) and apparent clearance was faster (1.5 ml/min/kg) than for adults (0.96 ml/min/kg).
In the population pharmacokinetic analysis conducted in patients from 1 month to 16 years of age, body weight was significantly correlated to apparent clearance (clearance increased with an increase in body weight) and apparent volume of distribution. Age also had an influence on both parameters. This effect was pronounced for the younger infants, and subsided as age increased, to become negligible around 4 years of age.
In both population pharmacokinetic analyses, there was about a 20 % increase of apparent clearance of levetiracetam when it was co-administered with an enzyme-inducing antiepileptic medicinal product.