Eur J Clin Pharmacol (1999) 55: 383±387
Ó Springer-Verlag 1999
PHARMACOKINETICS AND DISPOSITION
A. AÊsberg á H. Christensen á A. Hartmann E. Carlson á E. Molden á K. J. Berg
Pharmacokinetic interactions between microemulsion formulated cyclosporine A and diltiazem in renal transplant recipients
Received: 21 September 1998 / Accepted in revised form: 18 February 1999
Abstract Objective: Bilateral cyclosporin A (CsA) and diltiazem pharmacokinetic interactions have previously been investigated, however, not with the new microemulsion preconcentrate formulation of CsA (Sandimmun Neoral). In addition, the pharmacokinetic eects on the pharmacological active metabolites of diltiazem have not previously been investigated. We performed a pharmacokinetic interaction study in renal transplant recipients, measuring both unmetabolised CsA and diltiazem in addition to three of the main metabolites of diltiazem (MA, M1, M2). Methods: Nine CsA-treated renal transplant patients were treated with diltiazem, 90±120 mg b.i.d., for 4 weeks. Pharmacokinetic investigations were performed both before and at the end of the diltiazem treatment period. Six non-CsA-treated renal transplant patients served as controls of CsA interactions with diltiazem and its metabolites. Results: Diltiazem treatment resulted in a signi®cant mean increase in the area under the concentration±time curve (AUC) for CsA of 51(8)% (P < 0.008) and a peak concentration (Cmax) of 34(8)% (P < 0.05), without altering time to peak concentration (tmax). CsA, however, did not signi®cantly in¯uence diltiazem pharmacokinetics, though two of the metabolites (M1 and M2) tended to be increased. Conclusions: Diltiazem interacts signi®cantly with the pharmacokinetics of CsA in the new microemulsion This study was performed according to the current laws and directions for clinical trials in Norway A. AÊsberg á H. Christensen á A. Hartmann á E. Carlson á E. Molden Department of Pharmacology, School of Pharmacy, University of Oslo, Norway A. AÊsberg (&) á A. Hartmann á K.J. Berg Laboratory for Renal Physiology, Medical Department B, The National Hospital, N-0027 Oslo, Norway e-mail:
[email protected] Tel.: +47-2-2868323 (business), +47-2-2712773 (home) Fax: +47-2-2868303
formulation. Microemulsion-formulated CsA, however, did not show signi®cant interaction with diltiazem pharmacokinetics. Key words Cyclosporin A á Diltiazem á Kidney transplantation
Introduction Cyclosporin A (CsA)-induced hypertension and acute renal hypoperfusion [1, 2, 3, 4, 5] have been shown to be attenuated by concomitant use of the calcium-channel blockers (CCBs) dihydropyridine [6] and diltiazem [1]. Diltiazem is initially metabolised by N-demethylation and deacetylation to MA (N-demethyl-diltiazem) and M1 (deacetyl-diltiazem), respectively. Combination of these two metabolic pathways results in M2 (N-demethyl-deacetyl-diltiazem). Both M1 and M2 are further metabolised by an O-demethylation to M4 and M6 [7]. Two of the metabolites, MA and M1, have been reported to exercise relatively high vasodilating potency [7, 8]. A new microemulsion preconcentrate formulation of CsA (Sandimmun Neoral) that renders CsA available for absorption more independently of intestinal bile acids has been introduced. Both peak concentration (Cmax) and the area under the concentration-time curve (AUC) are higher, and intra-individual variations are lower than those obtained using the old formulation. Both diltiazem and CsA are predominantly metabolised by the CYP3A subfamily [9, 10], of which the CYP3A4 and CYP3A5 isoforms are abundantly expressed in the adult man [11]. Previous reports indicate that diltiazem has a major eect on CsA pharmacokinetics and that CsA has only a minor eect on diltiazem pharmacokinetics [12, 13, 14]. The microemulsion formulation of CsA and its bilateral interaction with diltiazem has however not been previously examined. The aim of this study was to investigate how diltiazem and CsA (microemulsion formulated) interact with each others pharmacokinetics in renal transplant
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recipients. Special emphasis was given to the interaction of CsA with diltiazem metabolism by measuring three of diltiazem's main metabolites.
Material and methods Patients Nine CsA-treated and six non-CsA-treated renal transplant recipients were included in the study. Demographic data are summarised in Table 1. All patients concluded the study. Informed consent was obtained according to the Declaration of Helsinki. The study was performed in accordance with Norwegian law and approved by the Regional Ethics Committee of Health Region II and by the Norwegian Medicines Control Authority, Oslo, Norway.
Study design
Plasma concentrations of diltiazem and three of its main metabolites (MA, M1 and M2) were analysed by means of high-performance liquid chromatography, after C18-solid-phase extraction [15]. The intra-assay and inter-assay coecients of variation were less than 5% and less than 6%, respectively, for all substances. Whole-blood concentration of non-metabolised CsA was analysed using a ¯uorescence polarisation immunoassay (FPIA, TDx, Abbott) [16]. Calculations Pharmacokinetic parameters included trough concentration (Ctrough), Cmax, time to peak concentration (tmax) and maintenance dose AUC over 11 h for diltiazem and 24 h for CsA. AUC was calculated using the trapezoidal method from 0 h to 11 h, and for CsA an AUC from 11 h to 24 h (AUC11±24) was added. This AUC11±24 was estimated using the logarithmic trapezoidal method, assuming the 24-h sample to be equal to Ctrough. Statistics
After a washout period of 4 weeks, all patients received diltiazem as a slow-release formulation (Cardizem Retard) for another 4 weeks, starting with 90 mg b.i.d. and increasing to 120 mg b.i.d. if systolic blood pressure was greater than 130 mmHg. Diltiazem pharmacokinetic investigations were performed in both groups at the end of the 4-week diltiazem treatment. CsA pharmacokinetic investigations were performed both following the washout period and at the end of the diltiazem treatment period in the CsA-treated group. The same individualised full 24-h dose of CsA (microemulsion formulation) was administered to CsA-treated patients in the morning of both pharmacokinetic investigation days. At the investigation following diltiazem treatment, 120 mg non-retard diltiazem (Cardizem) was administered to both groups. Whole blood samples for determination of CsA concentrations were drawn before (0 h) and 0.5, 1, 1.5, 2, 3, 4, 6, 9 and 11 h after drug administration. Plasma samples for diltiazem analysis were drawn before (0 h) and 0.5, 1, 2, 3, 4, 6, 9 and 11 h after drug administration. Table 1 Demographic baseline data and concomitant drugs during the study in renal transplant patients. tx renal transplantation; CsA cyclosporin A; Ccreat creatinine clearance (calculated from Cockraft and Gault's formula); A azathioprine; C calcitriol; F ¯uvastatin; No.
Chemical analysis
Sex
Age (years)
Weight (kg)
The results are presented as mean (SEM) unless speci®cally noted. Wilcoxon signed-rank test for paired statistical analysis was used. Dierences between treatments were analysed using the method of summary measures [17]. StatView 4.5 software was used for all statistical analysis (Abacus Concepts Inc. Berkeley, Calif.). The statistical power in this study to ®nd a 40% dierence in both CsA and diltiazem AUC was 90%, at a signi®cant level of 5%. P < 0.05 is considered statistically signi®cant.
Results Diltiazem eects on CsA pharmacokinetics CsA AUC was signi®cantly increased by an average of 51(8)% (P < 0.008), as was Cmax by an average of G glibenclamide; I isosorbide; Ins insulin; K ketanserin; L lovastatin; M metoprolol; N nitroglycerine; P prednisolone; R ranitidine; V vitamin B12 Ccreat (ml/min)
Time since tx. (years)
CsA-treated group 1 Male 2 Male 3 Male 4 Male 5 Female 6 Male 7 Female 8 Male 9 Female Median Range
72 52 47 70 51 38 53 31 57 52 31±72
88 74 64 85 60 83 89 94 59 83 59±94
63 62 43 59 43 43 59 41 19 43 19±63
6 5 8 2 5 7 5 6 3 5 2±8
Control group 10 11 12 13 14 15 Median Range
65 47 66 58 23 57 58 23±66
105 64 85 87 75 78 82 64±105
62 59 31 48 75 37 54 31±75
19 18 17 14 9 15 16 9±19
Male Female Male Male Male Male
CsA dose (mg/kg/day)
Other drugs
3.4 3.0 3.9 2.4 2.5 3.6 1.7 2.1 2.5 2.5 1.7±3.9
A, A, A, A, A, A, A, A, A,
P P F, M, P, R I, P F, P C, F, P M, P C, P L, M, P
A, A, A, A, A, A,
G, P I, Ins, N, P K, P P P L, P, V
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34(8)% (P < 0.05), without any change in tmax when CsA was administered concomitantly with diltiazem (Table 2, Fig. 1, lower panel). CsA eects on diltiazem pharmacokinetics CsA treatment did not signi®cantly interact with diltiazem pharmacokinetics. A tendency towards a righthand-shift of the diltiazem concentration-time curve was however present (Table 2, Fig. 1, upper panel). There were no signi®cant dierences in MA concentrations between the CsA-treated and the control group (P = 0.42). However, a similar right-hand shift as found for diltiazem was present (Fig. 2, upper panel). Mean M1 and M2 concentrations in the CsA-treated group tended to be higher than controls (P > 0.1) (Fig. 2, middle and lower panels). Due to analytical problems, patient number one was excluded from MA and M1 evaluation.
Discussion The present study con®rmed a signi®cant interaction of diltiazem with CsA pharmacokinetics in the same magnitude as previously reported [12, 13, 14, 18], also with the new CsA microemulsion formulation. CsA did, however, not interfere signi®cantly with diltiazem pharmacokinetics, although metabolites M1 and M2 tended to be elevated. The present study was designed to disclose a mean dierence in AUC of 40%. This level was chosen arbitrary to re¯ect clinically relevant interactions, although less-pronounced interactions may be relevant in speci®c individuals. CsA coadministration with diltiazem induced a tendency to a right-hand shift of the diltiazem concentraTable 2 Diltiazem and cyclosporin A (CsA) pharmacokinetics. Diltiazem pharmacokinetic parameters [mean (SEM)] after oral administration of 120 mg non-retard diltiazem and individualised full 24-h doses of CsA (Sandimmun Neoral) in CsA-treated patients (n = 9), and 120 mg non-retard diltiazem in control patients (n = 6) following 4 weeks of diltiazem treatment is shown to the left. CsA pharmacokinetics before and at the end of 4 weeks of diltiazem treatment in the CsA-treated patients (drug doses as above) is shown to the right. The area under the concentration± time curve (AUC) is the maintenance dose AUC over 11 h for diltiazem and 24 h for CsA. Cmax peak concentration; tmax time to reach peak concentration; Ctrough trough concentration Parameter
Diltiazem
CsA
CsA-treated Control patients patients
Before After diltiazem diltiazem
Ctrough (lg/l) 103 (18) 282 (31) Cmax (lg/l) AUC (lg h/l) 2188 (220) tmax (h) 3.3 (0.3) Drug dose 3.1 (0.2) (mg/kg/day)
119 (23) 315 (29) 2197 (172) 2.7 (0.3) 2.9 (0.2)
137 (20) 1336 (129) 7958 (682) 1.7 (0.1) 2.4 (0.2)
187 (14) 1791* (210) 11870* (1053) 1.9 (0.2) 2.3 (0.3)
* P < 0.05 compared with before diltiazem treatment
Fig. 1 Upper panel: Mean (SEM) plasma diltiazem concentrations in cyclosporin A (CsA)-treated patients (n = 9) and controls (n = 6) at the end of 4 weeks of diltiazem treatment. Lower panel: Mean (SEM) whole-blood CsA concentrations before and at the end of 4 weeks of diltiazem treatment (n = 9). Non-retard diltiazem (120 mg) was administered concomitantly to all patients after the 4 weeks of diltiazem treatment. The same individualised full 24-h dose of CsA (Sandimmun Neoral) was administered in each patient at both investigations
tion-time curve. Such absorption lag-phase has not been reported in studies using the old CsA formulation (Sandimmun) [12, 13, 14]. A possible explanation may be an interaction between diltiazem and CsA with P-glycoprotein, since both CsA and diltiazem are good substrates for P-glycoprotein [19, 20]. No change in MA plasma concentrations was shown with CsA coadministration. However, plasma concentrations of both M1 and M2 tended to be two- and ®vefold higher in the CsA-treated group than in controls. Both M1 and M2, but not MA, may be further Odemethylated, which indicates a possible interaction at the O-demethylating, rather than at the N-demethylating step. The subfamily CYP3A is only described to be responsible for N-demethylation of diltiazem [9], whereas the enzyme(s) responsible for the O-demethylation of diltiazem has not yet been characterised. In the case of human codeine metabolism, O-demethylation and Ndemethylation are catalysed by CYP2D6 and CYP3A4 respectively, and CsA inhibited both these reactions [21].
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relevant increase in AUC and Cmax of CsA in the same magnitude as previously reported for the old CsA formulation. CsA did not interact signi®cantly with diltiazem pharmacokinetics. Acknowledgements The skilled technical assistance of Janicke Narverud and Jean Stenstrùm at the Laboratory for Renal Physiology at the National Hospital and Lita Schram at the School of Pharmacy is acknowledged. In addition, we want to thank Stein Bergan and co-workers at the Institute of Clinical Biochemistry at the National Hospital for performing CsA analyses.
References
Fig. 2 Upper panel: Mean (SEM) plasma MA (N-demethyldiltiazem) concentrations in cyclosporin A (CsA)-treated patients (n = 8) and controls (n = 6). Middle panel: Mean (SEM) plasma M1 (deacetyl-diltiazem) concentrations in CsA-treated patients (n = 8) and controls (n = 6). Lower panel: Mean (SEM) plasma M2 (N-demethyl-deacetyl-diltiazem) concentrations in CsA-treated patients (n = 9) and controls (n = 6). For details see legends for Fig. 1
We therefore speculate that there might be an analogous situation in the metabolism of diltiazem. Interestingly, the isoenzyme CYP2D6 is a polymorphic enzyme, dierentiating humans into extensive metabolisers and poor metabolisers (about 7% of the European population) [22, 23, 24]. The high concentrations of M1 and M2 in the CsA-treated group were mainly due to only three of the patients. These patients showed about ®vefold higher M1 and about tenfold higher M2 concentrations than control (data not shown). We speculate that this might be due to poor O-demethylation in these three patients rather than a pharmacokinetic interaction. Conclusion Diltiazem interacted signi®cantly with microemulsion formulated CsA, leading to a substantial and clinically
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