Delayed introduction of reduced-dose tacrolimus, and renal function in liver transplantation: the 'ReSpECT' study.

We report a multicenter, prospective, randomized, open-label trial investigating the effect of lower levels and delayed introduction of tacrolimus on renal function in liver transplant recipients. Adult patients with good renal function undergoing primary liver transplant were randomized to either: group A (standard-dose tacrolimus [target trough levels >10 ng/mL] and corticosteroids; n = 183); group B (mycophenolate mofetil [MMF] 2g/day, reduced-dose tacrolimus [target trough levels

The population pharmacokinetics of amphotericin B colloidal dispersion in patients receiving bone marrow transplants.

The purpose of this study was to identify the pharmacokinetics of Amphotericin B Colloidal Dispersion in patients undergoing bone marrow transplantations with systemic fungal infections and to assess the influence of ABCD on renal function. Seventy-five patients (42 females, 33 males) with a median age of 34.5 years and median weight of 70.0 kg were enrolled in the study. The plasma concentration data was available in 51/75 patients and was best described by a two-compartment model; both plasma clearance and volume of distribution increased with escalating doses; the overall average terminal elimination half-life was 29 h. Serum creatinine values over the duration of therapy were available in 59/75 patients. Overall, there was no net change in renal function over the duration of therapy.

Pegylated-liposomal doxorubicin versus doxorubicin, bleomycin, and vincristine in the treatment of AIDS-related Kaposi's sarcoma: results of a randomized phase III clinical trial.

PURPOSE: Kaposi's sarcoma (KS), the most common neoplasm in patients with AIDS, is a significant clinical problem for which current therapies are frequently unsatisfactory. We conducted a randomized phase III clinical trial to compare the efficacy and toxicities of a new form of therapy, pegylated-liposomal doxorubicin, with standard combination chemotherapy in patients with advanced AIDS-related KS (AIDS-KS). PATIENTS AND METHODS: Two hundred fifty-eight patients with advanced AIDS-KS were randomly assigned to receive either pegylated-liposomal doxorubicin (20 mg/m2) or the combination of doxorubicin (20 mg/m2), bleomycin (10 mg/m2) and vincristine (1 mg) (ABV) every 14 days for six cycles. Standard response criteria, toxicity criteria, and predefined indicators of clinical benefit were examined to evaluate outcomes. RESULTS: Among 133 patients randomized to receive pegylated-liposomal doxorubicin, one achieved a complete clinical response and 60 achieved a partial response for an overall response rate of 45.9% (95% confidence interval [CI], 37% to 54%). Among 125 patients randomized to receive ABV, 31 achieved a partial response (24.8%; 95% confidence interval [CI], 17% to 32%). This difference was statistically significant (P < .001). In addition to objective responses, prospectively defined clinical benefits and toxicity outcomes also favored pegylated-liposomal doxorubicin. CONCLUSION: Pegylated-liposomal doxorubicin is more effective and less toxic than the standard combination chemotherapy regimen ABV for treatment of AIDS-KS.

Treatment of invasive fungal infections in renally impaired patients with amphotericin B colloidal dispersion.

Amphotericin B colloidal dispersion (ABCD) is a new formulation of conventional amphotericin B designed to minimize drug distribution in the kidney and reduce nephrotoxicity. We studied the safety and efficacy of ABCD in 133 renally compromised patients with invasive fungal infections. Patients had either nephrotoxicity from amphotericin B or preexisting renal disease. Intravenous treatment with ABCD (4 mg/kg of body weight daily) was administered for up to 6 weeks. Evaluations included clinical response to treatment and adverse events, with emphasis on changes in serum creatinine levels. ABCD did not appear to have an adverse effect on renal function: mean serum creatinine level tended to decrease slightly with days on therapy, and increases were not dose related. Complete or partial response to treatment was reported for 50% of the 133 intent-to-treat patients and 67% of the 58 evaluable patients.

Amphotericin B colloidal dispersion vs. amphotericin B as therapy for invasive aspergillosis.

To assess the efficacy and safety of amphotericin B colloidal dispersion (ABCD), 82 patients with proven or probable aspergillosis who were treated in clinical trials with ABCD were compared retrospectively with 261 patients with aspergillosis who were treated with amphotericin B at six cancer or transplant centers from January 1990 to June 1994. The groups were balanced in terms of underlying disease; ABCD recipients were younger and more likely to have preexisting renal insufficiency than were amphotericin B recipients (40.7% vs. 8.7%, respectively), and amphotericin B recipients were more likely to be neutropenic at baseline than were ABCD recipients (42.5% vs. 15.9%, respectively). Response rates (48.8%) and survival rates (50%) among ABCD-treated patients were higher than those (23.4% and 28.4%, respectively) among amphotericin B-treated patients (P < .001 for both comparisons). Renal dysfunction developed less frequently in ABCD recipients than in amphotericin B recipients (8.2% vs. 43.1%, respectively; P < .001). Multivariate analysis revealed that treatment group was the best predictor of response, mortality, and nephrotoxicity (ABCD: relative risk [RR] = 3.00, P = .002; RR = 0.35, P < .001; and RR = 0.13, P = .001; respectively). This retrospective study suggests that in the treatment of aspergillosis ABCD causes fewer nephrotoxic effects than amphotericin B and the efficacy of ABCD is at least comparable with that of amphotericin B.

Efficacy of pegylated-liposomal doxorubicin in the treatment of AIDS-related Kaposi's sarcoma after failure of standard chemotherapy.

PURPOSE: To determine the efficacy and safety of pegylated-liposomal doxorubicin in patients with AIDS and Kaposi's sarcoma (AIDS-KS) who experienced failure of standard chemotherapy. METHODS: Fifty-three patients with advanced AIDS-KS who experienced disease progression or intolerable toxicities while receiving standard doxorubicin/bleomycin/vincristine (ABV) or bleomycin/vincristine (BV) chemotherapy were identified from a cohort of patients who were then treated with pegylated-liposomal doxorubicin. Patients received 20 mg/m2 pegylated-liposomal doxorubicin (Doxil; Sequus Pharmaceuticals, Inc, Menlo Park, CA) every 3 weeks. RESULTS: Nineteen patients (36%) had a partial response (PR) and one patient had a clinical complete response (CCR). The median duration of response and time (from study entry) to treatment failure were 128 and 134 days, respectively. Of 28 patients who experienced disease progression while receiving combination regimens that contained standard doxorubicin, the PR rate was 32%, which suggests that the pegylated-liposomal encapsulation increases the therapeutic effect of doxorubicin. Patients obtained clinical benefits such as flattening of lesions (48%), improved lesion color (56%), relief of pain (45%), and loss of edema (83%). Forty-nine percent of patients had more than one clinical benefit. The most common adverse effect was leukopenia, which occurred in 40% of patients. Only 15% of patients had nausea and/or vomiting, none of which was severe; 9% experienced alopecia, also generally mild. CONCLUSION: Pegylated-liposomal doxorubicin offers a new alternative for treatment of patients who have experienced failure of standard chemotherapy for AIDS-KS.

Phase I study of amphotericin B colloidal dispersion for the treatment of invasive fungal infections after marrow transplant.

Amphotericin B colloidal dispersion (ABCD; Amphocil) was evaluated in a phase I dose-escalation study in 75 marrow transplant patients with invasive fungal infections (primarily Aspergillus or Candida species) to determine the toxicity profile, maximum tolerated dose, and clinical response. Escalating doses of 0.5-8.0 mg/kg in 0.5-mg/kg/patient increments were given up to 6 weeks. No infusion-related toxicities were observed in 32% of the patients; 52% had grade 2 and 5% had grade 3 toxicity. No appreciable renal toxicity was observed at any dose level. The estimated maximum tolerated dose was 7.5 mg/kg, defined by rigors and chills and hypotension in 3 of 5 patients at 8.0 mg/kg. The complete or partial response rate across dose levels and infection types was 52%. For specific types of infections, 53% of patients with fungemia had complete responses, and 52% of patients with pneumonia had complete or partial responses. ABCD was safe at doses to 7.5 mg/kg and had tolerable-infusion-related toxicity and demonstrable antifungal activity.

Population pharmacokinetics and renal function-sparing effects of amphotericin B colloidal dispersion in patients receiving bone marrow transplants.

The purpose of this study was to evaluate the pharmacokinetics of amphotericin B colloidal dispersion and its effect on creatinine clearance in bone marrow transplant patients with systemic fungal infections. Seventy-five patients (42 females and 33 males) with a median age of 34.5 years and a median weight of 70.0 kg were enrolled in the study. Patients received 1 of 15 dose levels (range, 0.5 to 8.0 mg/kg of body weight) daily for a mean duration of 28 days and a mean cumulative dose amount of 8 g. Plasma samples for amphotericin B determination (median number, 4; range, 2 to 30) and daily serum creatinine values were obtained for each patient. Iterative two-stage analysis, one of several approaches to population pharmacokinetic and pharmacodynamic modelling, was employed for the pharmacokinetic analysis. The plasma data were available for 51 of 75 patients and were best described by a two-compartment model. Both plasma clearance and volume of distribution increased with escalating doses; the overall average terminal elimination half-life was 29 h. Of the covariates studied, only body weight and dose size were significant. Serum creatinine values over the duration of therapy were available for 59 of 75 patients. Overall, there was no net change in renal function over the duration of therapy; 12 patients had > 30% increases in creatinine clearance, whereas 13 had > 30% decreases. No measure of amphotericin B colloidal dispersion exposure, demographic values, or concomitant treatment with other medications was related to changes in the creatinine clearance.

Organic anion transport by basal-lateral membranes: effect of PAH and furosemide on each other's transport.

The transport of organic anions by the kidney has been shown to be a carrier-mediated process. In an effort to learn more about this process, and examine the potential for two organic anions to compete for the same carrier site, studies were done which involved the transport of p-aminohippuric acid (PAH) and furosemide by vesicles made from basal-lateral membranes of rabbit kidney proximal tubules. Basal-lateral membranes were prepared by differential and ultracentrifugation. The transport was measured by using radiolabelled (3H) organic anions. The transport of each molecule was inhibited by probenecid, indicating that the carrier-mediated process for organic anion transport was functional in these studies. The results indicate that transport of PAH can be inhibited by furosemide in a concentration-dependent manner. This may indicate competition for the same carrier site. Inhibition of furosemide transport by PAH was not significant, perhaps due to much variability in the data. This variability may be due to nonspecific binding of furosemide to the vesicle, higher affinity of furosemide than of PAH for the receptor, or to the presence of more transport carriers for furosemide than for PAH. Experiments were done to determine the extent of nonspecific binding of furosemide. The results show that nonspecific binding of furosemide is extensive, indicating that this may contribute to the differences seen in the inhibition of transport. The data suggest that PAH and furosemide are transported by a common carrier-mediated process in the proximal tubule of the rabbit kidney.

Altered therapeutic range for quinidine after myocardial infarction and cardiac surgery.

Although most assays for measuring drug levels in serum determine the total concentration, effects from a drug are determined better by measuring the concentration of unbound (free) drug in serum. When the free fraction of a drug is constant, the total drug concentration may act as a good guide in predicting drug activity. However, if the free fraction is altered from normal, the serum concentration of the total drug may be misinterpreted. Quinidine has a high binding affinity for alpha-1-acid glycoprotein. We present the case of a woman who had a myocardial infarction; after cardiac surgery, she was found to have high concentrations of alpha-1-acid glycoprotein (228 mg/dL) and a low free fraction of quinidine (0.032). At that time the patient had a total concentration of quinidine of 33.9 mumol/L (11 micrograms/mL) but showed no signs or symptoms of toxicity because the concentration of free quinidine was not high. Physicians should be aware of the limitations of assays in determining the unbound concentration of drugs in serum. This awareness is particularly crucial with drugs that bind well to serum proteins, especially when pathologic conditions change the extent of binding.

Alloxan stimulates p-aminohippurate uptake in renal basal-lateral membranous vesicles.

In renal basal-lateral membranous vesicles, the probenecid-sensitive p-aminohippurate uptake was stimulated by alloxan. This stimulation of uptake was observed only after a lag period of 15 seconds, and it reached a maximal value after one minute. Stimulation was increased by 1 mM to 5 mM alloxan in a linear fashion. The effect was maximal and constant between 5 mM and 20 mM alloxan. Alloxan affected neither the glucose space of the vesicle nor the rate of transport or diffusion of glutamate, another organic anion. The mechanism of stimulation by alloxan was not clear. Its effect was blocked by the sulfhydryl reagent N-ethylmaleimide and weakly mimicked by H2O2, an oxidizing reagent. However, ninhydrin, a structural analogue of alloxan which reacts with sulfhydryl groups, and glucose, a neutral structural analogue of alloxan, failed to stimulate probenecid-sensitive uptake.

Effects of analogs of salicylate on p-aminohippurate uptake into basal-lateral membranous vesicles.

In basal-lateral membranes of the renal cortex, thiol substituted analogs of salicylate inhibited the uptake of p-aminohippurate (PAH). The mercury-containing analogs, thimerosal and mercaptide V (formed from 2 mol of thiosalicylate and 1 mol of Hg++), were highly inhibitory. Compared with probenecid, thimerosal and mercaptide V yielded dose-response curves of steeper slope and higher maximal effect. The dose-response curves of thimerosal and mercaptide V were similar in shape, although mercaptide V was more potent. The inhibition by thimerosal, mercaptide V and mersalyl acid, an anionic sulfhydryl reagent which also inhibits uptake of PAH ( Tse et al., J. Pharmacol. Exp. Ther. 226: 19-26, 1983), was found to be competitive with Ki values of 0.39 +/- 0.05, 0.12 +/- 0.06 and 0.05 +/- 0.02 mM, respectively. The inhibitory effects of thimerosal and mercaptide V were only partially reversible. Thimerosal and mercaptide V reacted 35 and 62%, respectively, with membrane sulfhydryl groups which may explain the nonreversibility of the inhibitor. The nonreversibility is probably not due to irreversible destruction of the vesicles, as the "glucose space" of the vesicles was not affected by these two compounds. That derivatives of salicylates capable of reacting with sulfhydryl groups were more inhibitory than thiosalicylate is consistent with a hypothesis that the PAH transporter contains a sulfhydryl group(s) essential for uptake. Based on the degree of inhibition, the degree of reversibility, the degree of membrane sulfhydryl group oxidation and the computer-generated three dimensional models of thimerosal, mercaptide V and mersalyl acid, a model of the PAH transporter is proposed.

Effects of trypsin and protein modification on the renal transporter of p-aminohippurate.

Basal-lateral membranous vesicles prepared from rabbit renal cortex exhibited Mg2+-stimulated, probenecid-inhibitable transport of p-aminohippurate (PAH). This uptake could be completely eliminated by incubating the membranes with trypsin at a weight ratio of 1:700 (trypsin/membrane protein). The loss of PAH uptake activity occurred in two stages. Over the first ten minutes of the vesicles' exposure to trypsin, there was a nearly linear loss, with respect to time, of about 80% of the PAH uptake activity. The remaining 20% of activity was resistant to further trypsin digestion for the next ten minutes, but by twenty-five minutes a total inactivation of the uptake activity occurred. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of normal and trypsin-treated vesicles showed very little degradation of proteins. However, two minor polypeptides (Mr - 410,000 and 388,000) were degraded during the first ten minutes of the membranes' exposure to trypsin. After twenty minutes of exposure, two other polypeptides (Mr = 94,500 and 87,500) were degraded. Chymotrypsin and clostripain also caused a loss of PAH transport activity. However, compared to the effects of trypsin, the effects of these two proteases were less complete, slower in onset, and for clostripain, a much higher concentration of enzyme was required. Other functions or properties of the vesicles including morphological appearance, degree of vesiculation, glucose space or Na+-dependent L-glutamate transport and Na+,K+-ATPase activity were not altered by the concentration of trypsin which abolished 80% of the transport of PAH. Thus, it is possible that one or more of the degraded polypeptides detected by polyacrylamide gel electrophoresis comprises the PAH transporter.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of divalent cations and sulfhydryl reagents on the p-aminohippurate (PAH) transporter of renal basal-lateral membranes.

A specific system of transport for p-aminohippurate (PAH) is demonstrated in rabbit renal basal-lateral membrane vesicles. The PAH uptake into an intravesicular space is inhibited by probenecid in concentrations above 0.2 mM. The transport is saturable and is also temperature-dependent with an optimum between 37 and 45 degrees C. Divalent cations are able to enhance the uptake 2- to 3-fold. The stimulatory effect of the divalent cations diminishes in the following order: Mg++ = Mn++, Ba++, Ca++ and Sr++. Maximum stimulation occurs between 2.5 and 5 mM Mg++. The divalent cation stimulatory effect is not the result of changes in the size of the vesicles, in the degree of vesiculation, in the net charge of the membrane or of a transient potential difference across the membrane. Several inhibitors, more inhibitory than probenecid, were found. These are: lithium diiodosalicylate; 4-acetamido-4'-isothiocyano 2,2'-disulfonic acid stilbene; the mercurials, mersalyl acid, p-chloromercuriphenyl sulfonate and Hg++; and 5,5'-dithiobis(nitrobenzoate). Among these, mersalyl acid is the most potent inhibitor for PAH uptake. Its inhibitory effect is probably a combination of its reactivity toward sulfhydryl groups and its anionic character. The results with sulfhydryl reagents indicate that the PAH transport system contains sulfhydryl groups which are essential for the uptake activity. These sulfhydryl groups are probably buried in a hydrophobic region within the lipoprotein matrix of the basal-lateral membrane.

Basal-lateral membranes from rabbit renal cortex prepared on a large scale in a zonal rotor.

Basal-lateral membranes from the renal cortex of the rabbit were isolated by sucrose gradient centrifugation in a zonal rotor which allows for a large-scale preparation of these membranes. A heterogeneous population of membranes (P4) which contained 29% of the (Na+ + K+)-ATPase found in the homogenate of renal cortex was prepared by differential centrifugation. When pellet P4 was subjected to centrifugation in a sucrose gradient the activity of (Na+ + K+)-ATPase, a marker for basal-lateral membranes, could be separated from enzymatic markers of other organelles. The specific activity of (Na+ + K+)-ATPase was enriched 12-fold at a density of 1.141 g/cm3. Membranes (P alpha) contained in the (Na+ + K+)-ATPase-rich fractions consisted primarily of closed vesicles which exhibited probenecid inhibitable transport of rho-aminohippurate. These membranes did not exhibit Na+-dependent, phlorizin-inhibitable D-glucose transport. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of proteins from P alpha revealed at least six major protein bands with molecular weights of 91000, 81000, 73000, 65000, 47000 and 38000. A small fraction of total alkaline phosphatase found in the homogenate was found in pellet P4. Membranes containing this alkaline phosphatase activity were distributed widely over the gradient, with peak activity found at a density of 1.141 g/cm3. In contrast, when brush borders were subjected to gradient centrifugation under the same conditions as P4, alkaline phosphatase was found in a narrow distribution, with peak activity at a density of 1.158 g/cm3. The principle subcellular localization of the alkaline phosphatase found in P4 could not be determined unambiguously from the data, but the activity did not seem to be primarily associated with classical brush borders.

Kinetics of D-glucose transport into renal membrane vesicles: measurements using a vacuum manifold apparatus.

The rapid kinetics of D-glucose uptake into membrane vesicles, prepared from the renal cortex of the rat, were measured. A vacuum manifold apparatus for the filtration of suspensions containing membrane vesicles and radiolabelled sugars was constructed to permit measurements of D-glucose accumulation within the vesicles at 8-s intervals. The rate of Na+-independent accumulation of D-glucose was nearly constant for the first 24 s while the rate for Na+-dependent uptake was always changing. While a linear relationship between Na+-dependent D-glucose accumulation and time could not be established for a time period as short as 8 s, the time for half maximum Na+-dependent D-glucose uptake could be estimated. A value of 4 s for half maximum accumulation D-glucose into membrane vesicles in the presence of sodium was obtained.

Hepatic disease and drug pharmacokinetics.

Recent clinical investigations and reports of theoretical models have provided considerable insight into mechanisms of hepatic drug elimination and into derangements that may occur in drug absorption and disposition in patients with hepatic disease. Carefully conducted and well controlled clinical studies have demonstrated that hepatic disease may alter substantially one or more pharmacokinetic parameters of drug absorption and disposition. Physiological models of hepatic drug elimination have emphasised the importance of physiological variables such as hepatic blood flow, protein binding and intrinsic clearance of the liver on hepatic drug elimination. Both clinical investigations and theoretical considerations have indicated that the influence of hepatic disease on the pharmacokinetics of a drug may be complex and may result in either unchanged, retarded or even accelerated drug elimination. Changes in response to drugs in patients with hepatic impairment add to this complexity. Although general guidelines may be formulated now to assist clinicians in constructing dosage regimens of several important drug classes (notably the benzodiazepines and barbiturates) in hepatic disease, it is not now possible to predict in an individual the influence of a specific hepatic disease on the disposition of a drug, with the exception that the oral availability of drugs with high hepatic extraction ratios is increased in patients with cirrhosis and protacaval shunting of blood. Attempts to correlate concentrations of endogenous substances (such as bilirubin), or the pharmacokinetics of model drugs (such as antipyrine), with the pharmacokinetics of drugs that are useful in patients with hepatic impairment have not resulted in clinically useful tests of hepatic drug elimination. Following the administration of a drug to a patient with hepatic impairment, careful monitoring of the patient and also monitoring of plasma or blood drug concentrations remain important considerations.