Transepithelial transport of biperiden hydrochloride in Caco-2 cell monolayers.

The aim of this research has been to determine the biperiden hydrochloride permeability in Caco-2 model, in order to classify it based on the Biopharmaceutics Classification System (BCS). The World Health Organization (WHO) as well as many other authors have provisionally assigned the drug as BCS class I (high solubility-high permeability) or III (high solubility-low permeability), based on different methods. We determined biperiden BCS class by comparing its permeability to 5 pre-defined compounds: atenolol and ranitidine hydrochloride (low permeability group) and metoprolol tartrate, sodium naproxen and theophylline (high permeability group). Since biperiden permeability was higher than those obtained for high permeability drugs, we classified it as a BCS class I compound. On the other hand, as no differences were obtained for permeability values when apical to basolateral and basolateral to apical fluxes were studied, this drug cannot act as a substrate of efflux transporters. As a consequence of our results, we suggest that the widely used antiparkinsonian drug, biperiden, should be candidate for a waiver of in vivo bioequivalence studies.

Amnesic effects of the anticholinergic drugs, trihexyphenidyl and biperiden: differences in binding properties to the brain muscarinic receptor.

An amnesic effect of anticholinergic drugs was previously described from several behavioral studies. We examined this effect induced by trihexyphenidyl and biperiden, clinically used in the parkinsonism and schizophrenic patients, by using passive avoidance tasks. Both of these drugs (0.1-10 mg/kg, s.c.) showed dose-dependent amnesic effects in the acquisition and retrieval phases. However, the effect induced by trihexyphenidyl was transient, whereas that of biperiden was long-lasting. To clarify the reason for the different duration of the amnesic activity, binding to the muscarinic receptor was examined. In the Scatchard analysis, trihexyphenidyl competed with [(3)H]quinuclidinyl benzilate ([(3)H]QNB) on the muscarinic receptor (showed increased K(d) and unchanged B(max) value), while biperiden decreased [(3)H]QNB binding (B(max) value) significantly. Furthermore, in an exchange assay for receptor inactivation, trihexyphenidyl binding to muscarinic receptors was exchanged by [(3)H]QNB completely, but biperiden decreased the exchangeable binding of [(3)H]QNB in a dose dependent manner (0.1-100 nM). These results suggested that the binding of trihexyphenidyl and biperiden to muscarinic receptor might be completely reversible and partially irreversible, respectively, whereas the K(i) values of these two drugs were similar. In conclusion, this difference in binding property may explain the difference in the time-course of the amnesic effect induced by trihexyphenidyl and biperiden.

Muscarinic receptor occupancy by biperiden in living human brain.

Anticholinergic drug is often used to treat extrapyramidal symptoms. We measured muscarinic cholinergic receptor (mAchR) occupancy by the oral administration of biperiden in eight healthy subjects using positron emission tomography (PET) and [11C]N-methyl-4-piperidylbenzilate (NMPB). After the baseline scan each subject underwent one or two post-dose PET scans. mAchR occupancy was 10-45% in the frontal cortex three hours after the oral administration of 4 mg of biperiden. The occupancy correlated with the plasma concentration of biperiden in a curvilinear manner.

The antiparkinsonian drugs budipine and biperiden are use-dependent (uncompetitive) NMDA receptor antagonists.

N-Methyl-D-aspartate- (NMDA-) evoked [3H]acetylcholine release in rabbit caudate nucleus slices was inhibited by the antiparkinsonian drugs budipine (1-tert-butyl-4,4-diphenylpiperidine) and biperiden (1-bicyclo[2.2.1.]hept-5-en-2-yl-1-phenyl-3-piperidino propanol) yielding functional Ki values of 4.6 and 8.8 microM. In contrast to the competitive antagonist 2-amino-5-phosphonopentaonate, budipine and biperidene significantly reduced both the apparent KD and the Emax value of NMDA. Moreover, they displaced [3H]MK-801 specifically bound to membranes of the same tissue, although with low affinity (IC50: 38 and 92 microM). It is concluded that budipine and biperiden are use-dependent (uncompetitive) antagonists at the NMDA receptor, binding to the receptor-linked ion channel, but probably not to the MK-801 binding site. NMDA antagonism may contribute to the antiparkinsonian effects of budipine.

Affinity and selectivity of biperiden enantiomers for muscarinic receptor subtypes.

The affinity of both the (+)- and the (-)-stereoisomer of biperiden for different muscarinic receptor subtypes was investigated in vitro in functional studies with field-stimulated rabbit vas deferens (M1-receptor), guinea-pig ileum (smooth muscle M2 beta-receptor) and rat left atrium (cardiac M2 alpha-receptor). (+)-Biperiden had its highest affinity to M1-receptors (pA2 = 9.07), had low affinity to cardiac M2 alpha-receptors (pA2 = 7.25) and intermediate affinity to ileal M2 beta-receptors (pA2 = 8.27). The ability of (+)-biperiden to discriminate between ileal M2 beta- and cardiac M2 alpha-receptors (factor = 10) was similar to that of 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP, factor = 9). In contrast, (-)-biperiden displayed low but nearly undistinguishable affinity for all muscarinic receptor subtypes studied (pA2 = 5.59 +/- 6.38). (+)-Biperiden discriminated strongly between M1- and cardiac M2 alpha-receptors (factor 66), thus being even more selective than pirenzepine (factor 28) which makes it one of the most M1-/cardiac M2 alpha-selective antimuscarinic drugs now available. These results indicate that (+)-biperiden could represent a further valuable tool for the characterization of muscarinic receptor subtypes.

Effects of fasting on biperiden pharmacokinetics in the rat.

The effects of fasting on the pharmacokinetics of biperiden in rats were examined. Total clearance of biperiden was greater than 90% ascribable to hepatic clearance and was essentially blood-flow dependent. The number of compartments in the preferred pharmacokinetic model of biperiden changed from three (for normal rats) to two (for fasted rats). The smaller mean residence time (MRT) values found for fasted rats were attributable to decreases in distribution volume. Biperiden showed much higher lipophilicity than haloperidol, thiopental, and hexobarbital, and its tissue-to-plasma partition coefficient in adipose tissue was 20-fold higher than that in muscle. The influence of changes in volumes of adipose tissue and muscle on distribution volume (Vdss/BW) was evaluated from tissue-to-plasma partition coefficients. The value of Vdss/BW was predicted to decrease with decrease of adipose tissue, and to increase with decrease of muscle tissue. These results suggest that the observed decrease of Vdss/BW in fasted rats reflects reduced capacity to trap biperiden in the body, especially in adipose tissue. Possible clinical implications of these results are discussed.

Fundamental pharmacokinetic properties of biperiden: tissue distribution and elimination in rabbits.

The pharmacokinetics of biperiden in rabbits were examined at three doses (0.2, 0.8, and 3.2 mg/kg i.v.). The data were interpreted in terms of a three-compartment open model with a linear excretion rate. The serum unbound fraction and the blood-to-plasma concentration ratio were determined as 0.39 and 1.2, respectively, over a wide concentration range (25-10000 ng/ml). Rapid and complete absorption from the injection site in muscle to the systemic circulation was observed. The bioavailability of muscular injection was unity. The hepatic extraction ratio was 0.94, and the high plasma clearance could be explained in terms of hepatic blood flow rate-limited elimination. The major tissues in which biperiden was distributed were fat and muscle. The highest tissue-to-plasma partition coefficient in the steady-state was obtained for the lung. These three tissues comprised 56% of the total distribution volume.

[Metabolism of antiparkinson drugs. An example of competitive hydroxylation]. / Der Metabolismus von Antiparkinson-Mitteln. Ein Beispiel für konkurrierende Hydroxylierungen.

The investigation of the metabolism of the antiparkinson drugs trihexyphenidyl (1), pridinol (2) and biperiden (3) revealed a graduate tendency for hydroxylation in the different structural elements: If alicyclic, saturated heterocyclic and aromatic ring systems are present in one compound like in 1, the alicyclic ring system is attacked predominately. The amount of metabolites with hydroxy-groups in the saturated heterocyclic ring is much lower, and no hydroxylation takes place in the aromatic ring. In drugs without alicyclic ring systems like 2 the saturated heterocyclus is attacked preferentially, but also some phenolic metabolites are formed. Consequently the following arrangement of falling hydroxylation-tendency can be established: Formula: see text. Probably this arrangement is of common validity and therefore a prediction on the hydroxylation-tendency of other compounds seems to be possible.