History of C2 monitoring in heart and liver transplant patients treated with cyclosporine microemulsion.

Therapeutic drug monitoring of CsA has evolved since the introduction of CsA microemulsion. The purpose of the present review is to summarize the history of CsA concentration 2 hours postdose (C2) monitoring in heart and liver transplantation. C2 has been shown to be the best single time point that correlates with the area-under-the-curve, with a correlation coefficient (r2) ranging between .83 and.93. C2 monitoring (300 to 600 ng/mL) has resulted in a significant clinical benefit in long-term heart and liver transplant patients compared to trough level (C0) monitoring. Moreover, a C2 range of 300 to 600 ng/mL resulted in a similar calcineurin inhibition compared to a C2 range of 700 to 1000 ng/mL or a C0 range of 100 to 200 ng/mL while being less injurious to renal function. In de novo liver transplant patients not receiving induction therapy, the achievement of a target C2 of 850 to 1400 ng/mL by postoperative day 3 has resulted in a low acute rejection rate. Furthermore, C2 monitoring has been associated with a lower rejection rate in hepatitis C virus (HCV)-negative patients and with an overall lesser severity of acute rejection compared to C0 monitoring. In de novo heart transplant patients who receive antithymocyte globulin induction, a lower C2 range may be sufficient to prevent rejection and renal dysfunction. Future studies should help to fine-tune the optimal C2 range in heart or liver transplant patients receiving induction therapy and different maintenance immunosuppressive combinations.

Effects of chronic N-acetylcysteine treatment on the actions of peroxynitrite on aortic vascular reactivity in hypertensive rats.

BACKGROUND: Peroxynitrite (ONOO-), the product of superoxide and nitric oxide, seems to be involved in vascular alterations in hypertension. OBJECTIVES: To evaluate the effects of ONOO- on endothelium-dependent and independent aortic vascular responsiveness, oxidized/reduced glutathione balance (GSSG/GSH), malondialdehyde aortic content, and the formation of 3-nitrotyrosine (3-NT), a stable marker of ONOO-, in N-acetylcysteine (NAC)-treated normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). RESULTS: In SHR only, NAC significantly reduced heart rate and systolic, but not diastolic, blood pressure. It also improved endothelium-dependent aortic relaxation in SHR, but not after exposure to ONOO-. Endothelium-dependent and independent aortic relaxations were markedly impaired by ONOO- in both strains of rat. NAC partially protected SHR against the ONOO- -induced reduction in endothelium-independent relaxation. Aortic GSSG/GSH ratio and malondialdehyde, which were higher in SHR than in WKY rats, showed a greater increase in SHR after exposure to ONOO-. NAC decreased GSSG/GSH and malondialdehyde in both strains of rat before and after exposure to ONOO-. The 3-NT concentration, which was similar in both strains of rat under basal conditions, was greater in SHR than in WKY rats after the addition of ONOO-, with a reduction only in NAC-treated SHR. CONCLUSIONS: These findings suggest an increased vulnerability of SHR aortas to the effects of ONOO- as compared with those of WKY rats. The selective improvements produced by NAC, in systolic arterial pressure, heart rate, aortic endothelial function, ONOO- -induced impairment of endothelium-independent relaxation, aortic GSSG/GSH balance, malondialdehyde content and 3-NT formation in SHR suggest that chronic administration of NAC may have a protective effect against aortic vascular dysfunction in the SHR model of hypertension.

Nonlinear kinetics and pharmacologic response to mibefradil.

BACKGROUND: Increasing oral doses of mibefradil (10 to 320 mg) decrease its apparent oral clearance; however, intravenous doses up to 80 mg do not reduce its systemic clearance. This study aimed to understand the mechanisms underlying the zero-order kinetics of mibefradil. METHODS: A group of 10 normotensive volunteers received 50 mg/day oral mibefradil for 8 days and, on days 1 and 8, 5 mg deuterated mibefradil by infusion. Ten additional volunteers observed the same protocol with a daily oral dose of 100 mg mibefradil. Serial blood samples were withdrawn, and mibefradil plasma concentrations were assayed by liquid chromatography-mass spectrometry. Blood pressure and heart rate were measured for 4 hours, and an ECG was performed 2 hours after drug administration. RESULTS: Repeated oral administration of 50 mg mibefradil generated zero-order kinetics secondary to a decrease in mibefradil systemic clearance. Compared with the 50-mg dose, single and repeated oral doses of 100 mg further decreased mibefradil clearance. Mibefradil bioavailability was not affected by increasing mibefradil doses. Mean diastolic blood pressure was decreased by single and repeated doses of 100 mg to the same extent. Repeated doses of 100 mg reduced heart rate and prolonged the PR and QTc, changes that were associated with mibefradil plasma concentrations. CONCLUSIONS: Repeated doses of 50 mg or doses of 100 mg mibefradil generated zero-order kinetics secondary to a decrease in hepatic extraction of the drug. Zero-order kinetics did not affect the response-concentration relationship of mibefradil.

Effect of antioxidant treatments on nitrate tolerance development in normotensive and hypertensive rats.

OBJECTIVES: To investigate the effect of chronic antioxidant treatments on the development of nitrate tolerance in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats by evaluating (i) coronary vascular reactivity, (ii) lipid peroxidation (malondialdehyde), and (iii) peroxynitrite formation (3-nitrotyrosine). METHODS: Tolerance was induced in 16-week-old male SHR and WKY, by 4 days of continuous treatment with nitroglycerin patches. Two groups were orally pre-treated (2-weeks) with antioxidants: N-acetyl-L-cysteine (NAC) or melatonin. Effects of serotonin (5-HT) and sodium nitroprusside (SNP) perfusion were tested in isolated Langendorff-perfused hearts. 3-Nitrotyrosine levels were measured in coronary sinus effluent and malondialdehyde in plasma. RESULTS: Nitrate tolerance reduced SNP-induced dilation in both strains. This alteration was differently improved by antioxidants: melatonin was effective in SHR, whereas NAC was effective in WKY. Tolerance also reduced 5-HT-mediated vasodilation in WKY, which was reversed by both antioxidants. By contrast, nitrate tolerance enhanced the vasoconstriction to 5-HT in SHR and both antioxidants prevented this response. Furthermore, tolerance was associated with higher malondialdehyde levels in both strains and with higher 3-nitrotyrosine levels in SHR. These changes were reversed by both antioxidants. CONCLUSIONS: A participation of oxidative stress was suggested during nitrate tolerance development, since antioxidants prevented the increase in lipid peroxidation and improved vascular responses to SNP and 5HT. Differential effects of antioxidants on SNP-induced vasodilation in SHR and WKY may suggest distinct mechanisms of tolerance development in hearts from hypertensive and normotensive rats. An increased peroxynitrite generation, expressed by higher 3-nitrotyrosine levels, could contribute to nitrate tolerance in the coronary circulation of SHR.

Two-hour cyclosporine level determination is the appropriate tool to monitor Neoral therapy.

To assess the safety profile of Neoral dose adjustment using cyclosporine (CsA) trough levels (C0) compared with levels obtained 2 h after the morning dose (C2), 30 stable adult heart transplant patients 1 yr or more after surgery were converted from Sandimmune to Neoral. After a baseline visit (before conversion), initial follow-up included two visits (2 and 4-6 wk after conversion). After the first visit, patients were randomized to Group I (C0: 100-200 ng/ml) or Group II (C2: 200-400 ng/ml). Abbreviated pharmacokinetics were obtained for the estimation of the AUC0-4 h. Renal function was assessed by serum creatinine and the cimetidine-modified creatinine clearance. C2 correlated better than C0 with the AUC0-4 h (r = 0.91 vs. 0.63). Initial Neoral dose (mg/kg/d) was similar in both groups (2.8 +/- 0.5 and 2.8 +/- 0.8), and was lower in Group II at the second visit (2.0 +/- 0.7 vs. 3.0 +/- 0.6, p = 0.0001). C2 levels decreased in Group II from 912 +/- 438 to 555 +/- 271 ng/ml (p = 0.01), without evidence of acute rejection on endomyocardial biopsies. After the second visit,-both groups were monitored with C2, and the range was increased to 300-600 ng/ml. At the last visit (additional follow-up of 5 +/- 1 months), Neoral dose (mg/kg/d) was reduced to 2.0 +/- 0.3 in Group I (p < 0.001) and 1.8 +/- 0.4 in Group II. Serum creatinine was lower in Group II at the second visit (138 +/- 59 vs. 168 +/- 37 mumol/L, p = 0.01) and was similar in both groups at the last visit. Neoral dose reduction based on C2 levels was not associated with acute rejection. The better correlation with the AUC0-4 h suggests that C2 may be more reliable than C0 for Neoral dose adjustment.

Comparison of neoral dose monitoring with cyclosporine through levels versus 2-hr postdose levels in stable liver transplant patients.

BACKGROUND: We reported that cyclosporine 2-hr postdose levels (C2) correlate better with the AUC0-4 hr than trough levels (C0) in heart transplant patients receiving Neoral. METHODS: We compared Neoral dose adjustment with C0 (group 1: 100-200 ng/ml) vs. C2 (group 2: 700-1000 ng/ml; group 3: 300-600 ng/ml) in 35 stable adult patients >1 year after liver transplantation. The AUC0-4hr was calculated, and simultaneous blood samples were obtained to measure calcineurin inhibition. Clinical benefit was defined as the absence of rejection and no increase in serum creatinine at the 7-month follow-up. RESULTS: C2 correlated better with the AUC0-4 hr than C0 (r=0.92 vs. r=0.40). Neoral dose increased by 17% and 39% in groups 1 and 2, and decreased by 18% in group 3 (P=0.002 vs. group 1 and P=0.0004 vs. group 2). Serum creatinine increased by 2.1% and 16% in groups 1 and 2, and decreased by 5.1% in group 3 (P=0.006 vs. group 2). A clinical benefit was observed in 37.5%, 23%, and 82% of patients in groups 1, 2, and 3 (P=0.03 vs. group 1 and P=0.01 vs. group 2). Calcineurin inhibition was similar in all groups at 2-hr (44+/-17%, 39+/-30%, and 44+/-35%), in spite of different Neoral doses (2.9+/-0.9, 4.0+/-1.8, and 2.6+/-1.3 mg/kg/day) and C2 (857+/-226, 922+/-274, and 588+/-274 ng/ml). CONCLUSIONS: C2 correlated better with the AUC0-4 hr than C0. Neoral dose monitoring with a C2 range of 300-600 ng/ml resulted in a lower dose and greater clinical benefit compared to C0 or a higher C2 in stable liver transplant patients. The correlation between calcineurin inhibition and clinical events deserves further research.

Efficacy and side-effects of cyclosporine dose monitoring with levels 6 h after the morning dose in heart transplant patients.

The purpose of this study was to compare CsA dose monitoring with trough levels (T0) vs. levels obtained 6 h after the morning dose of CsA (T6), with respect to the incidence of acute rejection and renal dysfunction, and the cumulative dose, as well as the cost of CsA after heart transplantation. Twenty consecutive adult heart transplant patients receiving quadruple sequential immunosuppression were prospectively randomized into CsA monitoring with T0 (Group I) vs. T6 levels (Group II). Oral CsA was started at a dosage of 2 mg/kg/d, 1-4 d after transplantation. The target range for either T0 or T6 was 150 to 250 ng/ml (enzyme multiplied immunologic technique), respectively. The CsA dose was increased or decreased by 0.5-1 mg/kg/d if the measured level was outside of the target range. Throughout the follow-up period (Group I, 11 +/- 2 months; Group II, 10 +/- 3 months), the incidence of acute rejection (ISHLT grade > or = 2) was 50% in each group. The left ventricular ejection fraction and serum creatinine were similar in both groups at 1 month and at the end of the follow-up. The maximal dose of CsA (mg/kg/d): 3.8 +/- 1 vs. 5 +/- 0.6 (P = 0.002), the minimal dose: 2.2 +/- 0.7 vs. 3.4 +/- 0.8 (P = 0.003), and the current dose: 2.6 +/- 0.6 vs. 3.5 +/- 1 (P = 0.02), were lower in Group II, as well as the cumulative dose of CsA (mg): 61,790 +/- 19,754 vs. 88,524 +/- 18,082 (P = 0.005), and its cost (CDN$): 3,589 +/- 1,116 vs. 5,106 +/- 1,045 (P = 0.005). In conclusion, CsA dose monitoring with T6 was associated with a 30% lower CsA dose and cost compared to T0, with the same effectiveness in the prevention of acute rejection, and similar cardiac and renal function.

Plasma levels of nicotine and safety of smokers wearing transdermal delivery systems during multiple simultaneous intake of nicotine and during exercise.

Although transdermal nicotine patches have been studied extensively under recommended conditions, the present studies were designed to assess the nicotine plasma levels and the safety of transdermal nicotine patches in smokers undergoing situations suspected to result in increased nicotine plasma levels. The first study examined the effects of increasing nicotine intake through sequential administration of a nicotine patch (day 2), a patch followed by consumption of nicotine gum (day 3), and a patch followed by gum consumption and cigarette smoking (day 4). In this study, nicotine plasma levels increased transiently after the addition of each nicotine source. Mean areas under the concentration-time curves from 0 to 24 hours (AUC0-24) for nicotine were 453 +/- 120 ng.hr/mL (day 2), 489 +/- 143 ng.hr/mL (day 3), and 485 +/- 143 ng.hr/mL (day 4). The second study evaluated the effects of physical exercise on the kinetics and the safety of two different types of nicotine transdermal devices: Nicoderm and Habitrol. The mean delivered dose of nicotine was higher with Nicoderm compared with Habitrol, and the two products were not considered to be bioequivalent. During a 20-minute exercise period, nicotine plasma levels increased by 13 +/- 9% for Nicoderm and 30 +/- 20% for Habitrol. This increase in nicotine plasma levels was probably related to the exercise-induced increase in peripheral circulation at the patch site. Results from both studies indicate a clinically nonsignificant increase in blood pressure and heart rate after the administration of nicotine. After exercise, subjects taking Habitrol tended to have a higher incidence of adverse events compared with baseline values. Safety profiles remained acceptable in both studies despite the increases in nicotine plasma levels. It was concluded that both superimposed nicotine sources and physical exertion result in short-lived plasma nicotine elevations and temporarily increase nicotine pharmacodynamic parameters without increased risk to the volunteers.

Stability of Clonazepam Suspension in HSC Vehicle.

The stability of clonazepam as an extemporaneous suspension compounded from tablets was studied. The clonazepam suspension (0.1 mg/mL) was prepared by incorporating pulverized 0.5-mg clonazepam tablets into the suspending Hospital for Sick children (HSC) Vehicle containing simple syrup and methylcellulose. This vehicle is also prepared extemporaneously. A clonazepam suspension and a clonazepam solution, both prepared in HSC Vehicle, were analyzed at various times during the 60-day study period against a clonazepam standard acetonitrile solutions stored in glass. These preparations using HSC Vehicle were stored at 4*C in a polyvinyl chloride (PVC) amber-colored plastic bottle. At various times during the 60 day study period, three samples from each bottle were removed and the concentration of clonazepam determined by a high-performance liquid chromatography assay procedure. This stability study demonstrates that storage of clonazepam suspension is safe for at least 60 days in a PVC bottle at 4*C, while the HSC solution rapidly loses the active ingredient by adsorption onto the plastic matrix due to the immediate availability towards the PVC.

Pharmacokinetics of epidural butorphanol in isoflurane-anaesthetized dogs.

Sixteen healthy male dogs were used at random in this protocol. The dogs were anaesthetized with isoflurane in oxygen. Eight of the dogs received 0.25 mg/kg of butorphanol (group B) and the others an equal volume of isotonic saline (group S) administered by a catheter inserted in the lumbosacral epidural space. Butorphanol concentrations in plasma and cerebrospinal fluid (CSF) were measured using high-performance liquid chromatography with electrochemical detection. Maximum concentration of butorphanol and time to obtain this concentration were 42.28 ng/mL at 13.88 min in blood, and 18.03 ng/mL at 30 min in CSF. Volume of distribution, clearance, mean distribution and elimination half-lives were respectively 4.39 L/kg, 2.02 L/h.kg, 16.5 min and 189.1 min. Mean isoflurane minimal alveolar concentration values for group B obtained following hind- or forelimb stimulation decreased by 31% after epidural butorphanol. Cutaneous analgesia (to pin-prick test) persisted for 3 h after the end of isoflurane anaesthesia in group B and was in correlation with the plasmatic analgesic dose of butorphanol (9 ng/mL). These results suggested that analgesia was predominantly obtained by action of butorphanol on the supraspinal structures following its vascular systemic absorption.

Presystemic elimination of morphine in anesthetized rabbits. Contribution of the intestine, liver, and lungs.

To assess the role of the intestine and the lung in the first-pass uptake of morphine relative to that of the liver, five groups of 6-7 New Zealand rabbits were used. A control group of conscious rabbits received 2 mg/kg of morphine iv. The remaining groups included anesthetized rabbits who received morphine into the aortic cross (2 mg/kg), the jugular vein (2 mg/kg), the portal vein (14 mg/kg), or into the duodenum (20 mg/kg). Multiple blood samples were withdrawn for 3 hr from the abdominal aorta, and morphine and morphine-6-glucuronide were assayed by HPLC. Anesthesia and surgery decreased morphine presystemic clearance from 264 +/- 14 to 194 +/- 12 ml/min/kg (p < 0.05). When morphine was injected into the aortic cross, the area under morphine plasma concentration-time curve (AUCM 0-->infinity) normalized by the dose was 7.81 +/- 0.56 10(-3) kg min/ml, a value that decreased to 5.26 +/- 0.36 (p < 0.05), 2.50 +/- 0.35 (p < 0.05), and 0.87 +/- 0.10 (p < 0.05) 10(-3) kg min/ml when morphine was injected before the lung, liver, or intestine, respectively. The extraction ratio of morphine by the lung, liver, and intestine was 0.33, 0.52, and 0.65, respectively. Compared with the aortic route, the AUCM6G 0-->infinity normalized by the dose ratio tended to be greater (p > 0.05) when morphine was injected into the jugular and portal veins, suggesting that morphine-6-glucuronide is not the major product result of morphine first-pass uptake.(ABSTRACT TRUNCATED AT 250 WORDS)