ANTI-INFLAMMATORY/IMMUNOSUPPRESSIVE
Optimization of Sampling Time for Cyclosporine Monitoring in Transplant Patients M. B. Regazzi, L. Gastaldi,
PharmD, Biol
H. Rondanelli,
D, L. Martinelli,
MD, PharmD,
Biol
MD, M. Vigano’,
MD
D,
Cyclosporine (GsA) dosing is based on CsA plasma or blood concentrations measured 12 to 24 hours after drug administration (trough levels). This study evaluated the relationship between the timing of GsA concentrations and subsequent pharmacokinetic parameters to predict an optimal sampling period. Plasma samples were obtained from 22 patients before their morning dose of CsA and at 2, 4, 6, 8, 10, and 12 hours after the dose on the 7th and on the 21st day after heart transplantation. The plasma samples were assayed by both HPLC and FPIA. The Cmax for CsA was achieved over a period ranging from 2 to 6 hours (mean/median = 4.7/4.0) during the day 7 and the day 21 studies. The mean (±SD) half-life was 3.2 (1.0) hours on day 7 and 2.9 (1.1) hours on day 21, (P> 0.05); the mean apparent oral clearance was 276(117) L/hr on the day 7 and 269 (209) L/hr on day 21, (P> 0.05). When CsA plasma concentration by either FPIA and HPLC was monitored, the drug concentration best correlated with AUG was found to correspond to the plasma samples taken 4 to 8 hours after drug administration. The authors conclude that trough blood sampling for therapeutic drug monitoring of GsA is not optimal, and that further studies are necessary to correlate concentration monitoring during the dosing interval with pharmacologic and toxicologic parameters.
C yclosporine
A (GsA) is a potent immunosuppressive agent used to prevent rejection of transplanted organs. It has a narrow therapeutic range, with some toxic effects that are concentration dependent,1’2 and therapeutic drug monitoring has proved to be a useful adjunct to successful immunosuppressive therapy with GsA. The importance of clinical pharmacokinetics in organ transplant patients, particularly with relation to GsA dosing, has been clearly demonstrated’ and has shown that (1) an optimal clinical response exists in the majority of patients when plasma or blood concentrations are kept to a relatively narrow range; (2) great differences exist among patients in their capacity to absorb, distribute, metabolize, and excrete drugs as a result of genetic and physiologic factors coupled with concomitant drug therapy; and (3) great differFrom the Department of Pharmacology (Drs. Regazzi, Rondanelli and Gastaldi), Division of Cardiosurgery (Dr. Martinelli), IRCCS-Policlinico
S. Matteo, Pavia; and the Department of Pharmacology (Dr. Rondanelii) and the Division of Cardiosurgery (Dr. Vigano’) University of Pavia, Pavia, Italy.Address for reprints: Dr. M. B. Regazzi, Department of Pharmacology, IRCCS-Policlinico S. Matteo, Pie Golgi 2, 27100 Pavia, Italy.
978
5
J Clin Pharmacol
1992;32:978-981
ences exist among patients as to the dose required to achieve an optimal clinical response. These considerations have produced a monitoring program where GsA dosage is based on GsA plasma or blood concentrations measured 12 to 24 hours after drug administration (trough levels). A thorough evaluation of this monitoring scheme has not been performed. Therefore the purpose of our study was to evaluate the relationship between the timing of GsA concentrations and subsequent pharmacokinetic parameters to predict an optimal sampling period.
MATERIAL Clinical
AND
METHODS
Protocol
Twenty-two patients undergoing heart transplantation surgery were enlisted for the study. The study was approved by the hospital committee and each patient consented to participation in the study. The patient’s ages ranged from 9 to 60 years (mean, 42) and the surgical procedures were conducted from March 1988 to March 1989. All patients in the study were maintained on the following immunosuppressive regimen: GsA 6 to 12
OPTIMIZATION
OF
SAMPLING
TIME
FOR
CYCLOSPORINE
MONITORING
mg/kg orally before transplantation and followed by an oral dose given every 12 hours, adjusted to obtain a 250- to 360-ng/mL plasma concentration in the first month and 60 to 180 ng/mL thereafter using a fluorescence polarization immunoassay (FPIA); azathioprine; intravenous methylprednisolone followed
that provides the best estimate of the oral drug clearance. Apparent oral drug clearance was simply calculated as the GsA dose/AUG value.
by
Cyclosporin
oral
prednisone;
antilymphocyte
globulin
or an-
tithymocyte globulin for 7 days. Other medications administered during the study period included antihypertensive agent (captopril, nifedipine, nitroprusside), sympathomimetics (isoproterenol), and diuretics (furosemide). Plasma samples were obtained from all patients before their morning oral dose of GsA and at 2, 4, 6, 8, 10, and 12 hours after the dose on the 7th and on the 21st day after heart transplantation. Plasma for GsA measurements was obtained as follows: the whole blood samples remained at room temperature (20#{176}C) for 2 hours before they were centrifuged at 4000 rpm to separate plasma from the cells. The plasma samples were then stored at -20#{176}G for less then 30 days until they were assayed by both high-performance liquid chromatography (HPLG) and FPIA. The routine biochemical measurements collected for patient monitoring of renal (serum creatinine) and hepatic (total bilirubin) function were recorded for each study day. Drug
Analysis
The FPIA assay was conducted in a manner designed by the manufacturer (Abbott Diagnostics, TDx fluorescence polarization analyzer, Rome, Italy). Plasma GsA samples also were assayed by the HPLG method as previously described.4’5 The detection limit of the HPLG assay was 15 mg/ mL. The interassay variability of the HPLG assay was less than 6%. The samples were assayed as pairs (weeks I and 3 together for each single patient). Pharmacokinetic
and
Statistical
Analysis
RESULTS A Pharmacokinetics
The Cmax for CsA was achieved over a period ranging from 2 to 6 hours (mean/median = 4.7/4.0 hours) during the day 7 and the day 21 studies (Figure 1). The plasma concentrations on day 7 and their corresponding AUGs were not significantly different from those obtained on day 21. No significant differences were observed between terminal half-lives and clearance values obtained by HPLG on day 7 and the correspondent values obtained on day 21. The mean half-life ± standard deviation was 3.2 ± 1.0 hours on day 7 and 2.9 ± 1.1 hours on day 21. The mean apparent oral clearance of GsA in these patients was 276 ± 117 L/hour on the day 7 and 269 ± 209 L/hour on day 21. No statistically significant difference between the two periods was observed for concentration or AUG when plasma was assayed by FPIA. When considering the nonspecific FPIA assay versus the specific HPLG assay, no significant difference was observed in the ratio of AUC values obtained by FPIA/HPLG observed during the first week (mean! median: 4.0/3.9) and the third week (mean/median: 3.6/3.1). Biochemistry The ±
mean
plasma
0.1 mg/dL
creatinine
on day
7
and
concentration 1.2 ± 0.2 mg/dL
was
0.9
on day
21
S C
The area under the plasma concentration-time curve during the dosing interval (AUC) and the terminal elimination half life (t#{189})were calculated using the nonlinear regression program SIPHAR.6 The differences in maximum peak plasma concentration (Cmax), time to maximum peak plasma concentration (tmax), t#{189}, and AUG between the two study periods was performed using the Student’s t test for paired samples. A P < 0.05 was considered significant for all statistical analysis. The linear correlation coefficient (r) between the AUG of GsA during a dosing interval and plasma concentration (G’) at a given time (t’) was evaluated to identify a sampling time during the dosing interval
ANTI-INFLAMMATORY/IMMUNOSUPPRESSIVE
a’ -J S E S
a-
0.0
2.0
Time
(Hours)
Figure. Time course of mean + SD plasma GsA concentrations during a 12-hour dosing interval on the day 7 and day 21 studies after heart transplantation. Symbols are (0) HPLC day 7, () HPLC day 21, (X) FPIA day 7, (is) FPIA day 21.
979
REGAZZI
surgery (P < .01) 1.8 ± 0.7 mg/dL
after was
mg/dL
on
the
21st
whereas on
day
mean bilirubin level 7th day and 1.2 ± 0.4 after transplantation (P
the
Optimization of Sampling Time for Cyclosporine Monitoring in Transplant Patients M. B. Regazzi, L. Gastaldi,
PharmD, Biol
H. Rondanelli,
D, L. Martinelli,
MD, PharmD,
Biol
MD, M. Vigano’,
MD
D,
Cyclosporine (GsA) dosing is based on CsA plasma or blood concentrations measured 12 to 24 hours after drug administration (trough levels). This study evaluated the relationship between the timing of GsA concentrations and subsequent pharmacokinetic parameters to predict an optimal sampling period. Plasma samples were obtained from 22 patients before their morning dose of CsA and at 2, 4, 6, 8, 10, and 12 hours after the dose on the 7th and on the 21st day after heart transplantation. The plasma samples were assayed by both HPLC and FPIA. The Cmax for CsA was achieved over a period ranging from 2 to 6 hours (mean/median = 4.7/4.0) during the day 7 and the day 21 studies. The mean (±SD) half-life was 3.2 (1.0) hours on day 7 and 2.9 (1.1) hours on day 21, (P> 0.05); the mean apparent oral clearance was 276(117) L/hr on the day 7 and 269 (209) L/hr on day 21, (P> 0.05). When CsA plasma concentration by either FPIA and HPLC was monitored, the drug concentration best correlated with AUG was found to correspond to the plasma samples taken 4 to 8 hours after drug administration. The authors conclude that trough blood sampling for therapeutic drug monitoring of GsA is not optimal, and that further studies are necessary to correlate concentration monitoring during the dosing interval with pharmacologic and toxicologic parameters.
C yclosporine
A (GsA) is a potent immunosuppressive agent used to prevent rejection of transplanted organs. It has a narrow therapeutic range, with some toxic effects that are concentration dependent,1’2 and therapeutic drug monitoring has proved to be a useful adjunct to successful immunosuppressive therapy with GsA. The importance of clinical pharmacokinetics in organ transplant patients, particularly with relation to GsA dosing, has been clearly demonstrated’ and has shown that (1) an optimal clinical response exists in the majority of patients when plasma or blood concentrations are kept to a relatively narrow range; (2) great differences exist among patients in their capacity to absorb, distribute, metabolize, and excrete drugs as a result of genetic and physiologic factors coupled with concomitant drug therapy; and (3) great differFrom the Department of Pharmacology (Drs. Regazzi, Rondanelli and Gastaldi), Division of Cardiosurgery (Dr. Martinelli), IRCCS-Policlinico
S. Matteo, Pavia; and the Department of Pharmacology (Dr. Rondanelii) and the Division of Cardiosurgery (Dr. Vigano’) University of Pavia, Pavia, Italy.Address for reprints: Dr. M. B. Regazzi, Department of Pharmacology, IRCCS-Policlinico S. Matteo, Pie Golgi 2, 27100 Pavia, Italy.
978
5
J Clin Pharmacol
1992;32:978-981
ences exist among patients as to the dose required to achieve an optimal clinical response. These considerations have produced a monitoring program where GsA dosage is based on GsA plasma or blood concentrations measured 12 to 24 hours after drug administration (trough levels). A thorough evaluation of this monitoring scheme has not been performed. Therefore the purpose of our study was to evaluate the relationship between the timing of GsA concentrations and subsequent pharmacokinetic parameters to predict an optimal sampling period.
MATERIAL Clinical
AND
METHODS
Protocol
Twenty-two patients undergoing heart transplantation surgery were enlisted for the study. The study was approved by the hospital committee and each patient consented to participation in the study. The patient’s ages ranged from 9 to 60 years (mean, 42) and the surgical procedures were conducted from March 1988 to March 1989. All patients in the study were maintained on the following immunosuppressive regimen: GsA 6 to 12
OPTIMIZATION
OF
SAMPLING
TIME
FOR
CYCLOSPORINE
MONITORING
mg/kg orally before transplantation and followed by an oral dose given every 12 hours, adjusted to obtain a 250- to 360-ng/mL plasma concentration in the first month and 60 to 180 ng/mL thereafter using a fluorescence polarization immunoassay (FPIA); azathioprine; intravenous methylprednisolone followed
that provides the best estimate of the oral drug clearance. Apparent oral drug clearance was simply calculated as the GsA dose/AUG value.
by
Cyclosporin
oral
prednisone;
antilymphocyte
globulin
or an-
tithymocyte globulin for 7 days. Other medications administered during the study period included antihypertensive agent (captopril, nifedipine, nitroprusside), sympathomimetics (isoproterenol), and diuretics (furosemide). Plasma samples were obtained from all patients before their morning oral dose of GsA and at 2, 4, 6, 8, 10, and 12 hours after the dose on the 7th and on the 21st day after heart transplantation. Plasma for GsA measurements was obtained as follows: the whole blood samples remained at room temperature (20#{176}C) for 2 hours before they were centrifuged at 4000 rpm to separate plasma from the cells. The plasma samples were then stored at -20#{176}G for less then 30 days until they were assayed by both high-performance liquid chromatography (HPLG) and FPIA. The routine biochemical measurements collected for patient monitoring of renal (serum creatinine) and hepatic (total bilirubin) function were recorded for each study day. Drug
Analysis
The FPIA assay was conducted in a manner designed by the manufacturer (Abbott Diagnostics, TDx fluorescence polarization analyzer, Rome, Italy). Plasma GsA samples also were assayed by the HPLG method as previously described.4’5 The detection limit of the HPLG assay was 15 mg/ mL. The interassay variability of the HPLG assay was less than 6%. The samples were assayed as pairs (weeks I and 3 together for each single patient). Pharmacokinetic
and
Statistical
Analysis
RESULTS A Pharmacokinetics
The Cmax for CsA was achieved over a period ranging from 2 to 6 hours (mean/median = 4.7/4.0 hours) during the day 7 and the day 21 studies (Figure 1). The plasma concentrations on day 7 and their corresponding AUGs were not significantly different from those obtained on day 21. No significant differences were observed between terminal half-lives and clearance values obtained by HPLG on day 7 and the correspondent values obtained on day 21. The mean half-life ± standard deviation was 3.2 ± 1.0 hours on day 7 and 2.9 ± 1.1 hours on day 21. The mean apparent oral clearance of GsA in these patients was 276 ± 117 L/hour on the day 7 and 269 ± 209 L/hour on day 21. No statistically significant difference between the two periods was observed for concentration or AUG when plasma was assayed by FPIA. When considering the nonspecific FPIA assay versus the specific HPLG assay, no significant difference was observed in the ratio of AUC values obtained by FPIA/HPLG observed during the first week (mean! median: 4.0/3.9) and the third week (mean/median: 3.6/3.1). Biochemistry The ±
mean
plasma
0.1 mg/dL
creatinine
on day
7
and
concentration 1.2 ± 0.2 mg/dL
was
0.9
on day
21
S C
The area under the plasma concentration-time curve during the dosing interval (AUC) and the terminal elimination half life (t#{189})were calculated using the nonlinear regression program SIPHAR.6 The differences in maximum peak plasma concentration (Cmax), time to maximum peak plasma concentration (tmax), t#{189}, and AUG between the two study periods was performed using the Student’s t test for paired samples. A P < 0.05 was considered significant for all statistical analysis. The linear correlation coefficient (r) between the AUG of GsA during a dosing interval and plasma concentration (G’) at a given time (t’) was evaluated to identify a sampling time during the dosing interval
ANTI-INFLAMMATORY/IMMUNOSUPPRESSIVE
a’ -J S E S
a-
0.0
2.0
Time
(Hours)
Figure. Time course of mean + SD plasma GsA concentrations during a 12-hour dosing interval on the day 7 and day 21 studies after heart transplantation. Symbols are (0) HPLC day 7, () HPLC day 21, (X) FPIA day 7, (is) FPIA day 21.
979
REGAZZI
surgery (P < .01) 1.8 ± 0.7 mg/dL
after was
mg/dL
on
the
21st
whereas on
day
mean bilirubin level 7th day and 1.2 ± 0.4 after transplantation (P
the
