Efficacy and tolerability of the DPP-4 inhibitor alogliptin combined with pioglitazone, in metformin-treated patients with type 2 diabetes.

CONTEXT: Optimal management of type 2 diabetes remains an elusive goal. Combination therapy addressing the core defects of impaired insulin secretion and insulin resistance shows promise in maintaining glycemic control. OBJECTIVE: The aim of the study was to assess the efficacy and tolerability of alogliptin combined with pioglitazone in metformin-treated type 2 diabetic patients. DESIGN, SETTING, AND PATIENTS: We conducted a multicenter, randomized, double-blind, placebo-controlled, parallel-arm study in patients with type 2 diabetes. INTERVENTIONS: The study consisted of 26-wk treatment with alogliptin (12.5 or 25 mg qd) alone or combined with pioglitazone (15, 30, or 45 mg qd) in 1554 patients on stable-dose metformin monotherapy (≥1500 mg) with inadequate glycemic control. MAIN OUTCOME MEASURE: The primary endpoint was change in glycosylated hemoglobin (HbA(1c)) from baseline to wk 26. Secondary endpoints included changes in fasting plasma glucose and ß-cell function. Primary analyses compared pioglitazone therapy [all doses pooled, pioglitazone alone (Pio alone); n = 387] with alogliptin 12.5 mg plus any dose of pioglitazone (A12.5+P; n = 390) or alogliptin 25 mg plus any dose of pioglitazone (A25+P; n = 390). RESULTS: When added to metformin, the least squares mean change (LSMΔ) from baseline HbA(1c) was -0.9 ± 0.05% in the Pio-alone group and -1.4 ± 0.05% in both the A12.5+P and A25+P groups (P < 0.001 for both comparisons). A12.5+P and A25+P produced greater reductions in fasting plasma glucose (LSMΔ = -2.5 ± 0.1 mmol/liter for both) than Pio alone (LSMΔ = -1.6 ± 0.1 mmol/liter; P < 0.001). A12.5+P and A25+P significantly improved measures of ß-cell function (proinsulin:insulin and homeostasis model assessment of ß-cell function) compared to Pio alone, but had no effect on homeostasis model assessment of insulin resistance. The LSMΔ body weight was 1.8 ± 0.2, 1.9 ± 0.2, and 1.5 ± 0.2 kg in A12.5+P, A25+P, and Pio-alone groups, respectively. Hypoglycemia was reported by 1.0, 1.5, and 2.1% of patients in the A12.5+P, A25+P, and Pio-alone groups, respectively. CONCLUSIONS: In type 2 diabetic patients inadequately controlled by metformin, the reduction in HbA(1c) by alogliptin and pioglitazone was additive. The decreases in HbA(1c) with A12.5+P and A25+P were similar. All treatments were well tolerated.

Pharmacokinetics of alogliptin when administered with food, metformin, or cimetidine: a two-phase, crossover study in healthy subjects.

OBJECTIVE: The dipeptidyl peptidase-4 inhibitor alogliptin, under development for treatment of Type 2 diabetes, primarily is excreted renally. This study investigated (1) the effect of food on alogliptin pharmacokinetics and tolerability and (2) pharmacokinetic interactions between alogliptin and metformin or cimetidine and tolerability of alogliptin when administered with either drug. METHODS: This randomized, open-label, two-phase, crossover study recruited healthy adults. In the single-dose phase, 36 subjects received an oral dose of alogliptin 100 mg under fed or fasted conditions. In the multiple-dose phase, subjects in one arm (n = 17) received 6 days each of alogliptin 100 mg once daily (q.d.), metformin 1,000 mg twice daily (b.i.d), and alogliptin q.d. + metformin b.i.d; subjects in the other arm (n = 18) received 6 days each of alogliptin 100 mg q.d., cimetidine 400 mg q.d., and alogliptin q.d. + cimetidine b.i.d. Pharmacokinetic parameters were determined after the last dose in each period. Tolerability was assessed through adverse events and clinical findings. RESULTS: Food had no effect on alogliptin area under the concentration-time curve (AUC) from 0 h to infinity and a small, clinically insignificant effect on maximum plasma concentration (C(max)) (fed/fasted least squares (LS) geometric mean ratio, 0.856; 90% confidence interval (CI), 0.798 - 0.917). Metformin and cimetidine did not affect alogliptin pharmacokinetics. Alogliptin had no effect on metformin C(max) and a small, clinically insignificant effect on AUC over the dosing interval ((alogliptin + metformin)/metformin LS geometric mean ratio, 1.19; 90% CI, 1.095 - 1.291). Alogliptin did not affect cimetidine pharmacokinetics. Alogliptin tolerability was similar under all conditions. CONCLUSION: Alogliptin can be administered without regard to meals and with metformin or cimetidine without the need for dose adjustment.

Alogliptin added to insulin therapy in patients with type 2 diabetes reduces HbA(1C) without causing weight gain or increased hypoglycaemia.

AIMS: To assess the efficacy and safety of alogliptin added to insulin in patients with type 2 diabetes inadequately controlled with insulin alone or combined with metformin. METHODS: In this 26-week, double-blind, placebo-controlled study, 390 patients were randomized to receive alogliptin 12.5 mg (n = 131), alogliptin 25 mg (n = 129) or placebo (n = 130) once daily, as add-on to stable insulin therapy with or without metformin. The primary endpoint was change in haemoglobin A(1C) (HbA(1C)) at week 26. RESULTS: At week 26, mean HbA(1C) changes from the mean baseline value of 9.3% were significantly greater for alogliptin 12.5 mg (-0.63 +/- 0.08%) and alogliptin 25 mg (-0.71 +/- 0.08%) than placebo (-0.13 +/- 0.08%; p < 0.001). Significantly greater proportions of patients receiving alogliptin 12.5 or 25 mg than placebo had HbA(1C) decreases of > or =0.5, > or =1.0 and > or =1.5%. Insulin doses remained unchanged, and there were no differences in the proportions of patients experiencing hypoglycaemia among placebo (24%), alogliptin 12.5 mg (27%) and alogliptin 25 mg (27%). Mean weight increases from baseline at week 26 were similar for placebo (0.6 +/- 0.2 kg), alogliptin 12.5 mg (0.7 +/- 0.2 kg) and alogliptin 25 mg (0.6 +/- 0.2 kg). Incidences of overall adverse events, and of gastrointestinal, dermatological and infection-related events, were similar among groups. CONCLUSIONS: Adding alogliptin to previous insulin therapy (with or without metformin) significantly improved glycaemic control in patients with type 2 diabetes inadequately controlled on insulin, without causing weight gain or increasing the incidence of hypoglycaemia. Further studies are warranted to explore the role of alogliptin added to optimized basal insulin regimens.

Efficacy and safety of the dipeptidyl peptidase-4 inhibitor alogliptin in patients with type 2 diabetes inadequately controlled by glyburide monotherapy.

AIM: To evaluate the efficacy and safety of alogliptin, a potent and highly selective dipeptidyl peptidase-4 (DPP-4) inhibitor, in combination with glyburide in patients with type 2 diabetes inadequately controlled by sulphonylurea monotherapy. METHODS: After a 2-week screening period, adult patients 18-80 years of age entered a 4-week run-in/stabilization period in which they were switched from their own sulphonylurea medication to an equivalent dose of glyburide (open label) plus placebo (single blind). After the run-in period, patients were randomly assigned to double-blind treatment with alogliptin 12.5 mg (n = 203), alogliptin 25 mg (n = 198), or placebo (n = 99) for 26 weeks. The primary end-point was change from baseline to week 26 in glycosylated haemoglobin (HbA1c). Secondary end-points included clinical response rates and changes in fasting plasma glucose, beta-cell function (fasting proinsulin, insulin, proinsulin/insulin ratio, and C-peptide, and homeostasis model assessment beta-cell function), body weight, and safety end-points [adverse events (AEs), clinical laboratory tests, vital signs and electrocardiographic readings]. RESULTS: The study population had a mean age of 57 years and a mean disease duration of 8 years; it was well balanced for gender (52% women) and was mainly white (71%). The mean baseline HbA1c was approximately 8.1% in each group. Significantly greater least squares (LS) mean reductions in HbA1c were seen at week 26 with alogliptin 12.5 mg (-0.38%) and 25 mg (-0.52%) vs. placebo (+0.01%; p < 0.001), and more patients in the alogliptin 25-mg group had HbA1c levels < or =7.0% at week 26 (34.8%, p = 0.002) vs. placebo (18.2%). Proportionately more patients in the alogliptin 12.5 mg (47.3%) and 25 mg (50.5%) groups had an HbA1c reduction > or =0.5% from baseline compared with patients in the placebo group (26.3%; p < 0.001). Minor improvements in individual markers of beta-cell function were seen with alogliptin, but no significant treatment group differences were noted relative to placebo. Minor LS mean changes in body weight were noted across groups (placebo, -0.20 kg; alogliptin 12.5 mg, +0.60 kg; alogliptin 25 mg, +0.68 kg). AEs were reported for 63-64% of patients receiving alogliptin and 54% of patients receiving placebo. Few AEs were treatment limiting (2.0-2.5% across groups), and serious AEs (2.0-5.6%) were infrequent, similar across groups, and generally considered not related to treatment. The incidences of hypoglycaemia for placebo, alogliptin 12.5 mg and alogliptin 25 mg groups were 11.1, 15.8 and 9.6% respectively. CONCLUSIONS: In patients with type 2 diabetes inadequately controlled by glyburide monotherapy, the addition of alogliptin resulted in clinically significant reductions in HbA1c without increased incidence of hypoglycaemia.

Efficacy and safety of adding the dipeptidyl peptidase-4 inhibitor alogliptin to metformin therapy in patients with type 2 diabetes inadequately controlled with metformin monotherapy: a multicentre, randomised, double-blind, placebo-controlled study.

AIMS: To evaluate the efficacy and safety of alogliptin, a new dipeptidyl peptidase-4 inhibitor, for 26 weeks at once-daily doses of 12.5 and 25 mg in combination with metformin in patients whose HbA(1c) levels were inadequately controlled on metformin alone. METHODS AND PATIENTS: Patients with type 2 diabetes and inadequate glycaemic control (HbA(1c) 7.0-10.0%) were randomised to continue a stable daily metformin dose regimen (> or = 1500 mg) plus the addition of placebo (n = 104) or alogliptin at once-daily doses of 12.5 (n = 213) or 25 mg (n = 210). HbA(1c), insulin, proinsulin, C-peptide and fasting plasma glucose (FPG) concentrations were determined over a period of 26 weeks. RESULTS: Alogliptin at either dose produced least squares mean (SE) decreases from baseline in HbA(1c) of -0.6 (0.1)% and in FPG of -17.0 (2.5) mg/dl [-1.0 (0.1) mmol/l], decreases that were significantly (p < 0.001) greater than those observed with placebo. The between treatment differences (alogliptin - placebo) in FPG reached statistical significance (p < 0.001) as early as week 1 and persisted for the duration of the study. Overall, adverse events (AEs) observed with alogliptin were not substantially different from those observed with placebo. This includes low event rates for gastrointestinal side effects and hypoglycaemic episodes. There was no dose-related pattern of AE reporting between alogliptin groups and few serious AEs were reported. CONCLUSION: Alogliptin is an effective and safe treatment for type 2 diabetes when added to metformin for patients not sufficiently controlled on metformin monotherapy.

Safety of tacrolimus in patients with rheumatoid arthritis: long-term experience.

OBJECTIVE: To evaluate the long-term safety of tacrolimus 3 mg/day in patients with rheumatoid arthritis (RA). METHODS: Patients with active RA who had discontinued all DMARDs for at least 2 weeks and had at least five tender/painful joints and three swollen joints, and required DMARD treatment in the opinion of the investigator, were enrolled into this open-label long-term safety trial. In addition, patients who had completed at least 3 months of treatment with tacrolimus 2 mg/day, tacrolimus 3 mg/day or placebo in a Phase III double-blind efficacy trial were allowed to roll over into this study. This latter group of patients did not have to fulfil any joint count requirements prior to entry into the long-term safety study, provided that no more than 14 days had elapsed between the end of their participation in the double-blind study and screening for the long-term safety study. All patients enrolled received tacrolimus 3 mg/day in addition to their current regimen of NSAIDs and corticosteroids. RESULTS: 896 patients received at least one dose of tacrolimus 3 mg. The median duration of treatment was 359 days. 145 patients (16.2%) withdrew from the study for adverse events possibly or probably related to tacrolimus, 33 patients (3.7%) withdrew from the study for adverse events unrelated to tacrolimus and 112 (12.5%) withdrew for lack of efficacy. No adverse event with an incidence >0.7% appeared for the first time after the first 3 months of treatment with 3 mg tacrolimus. 529 patients (59%) experienced an adverse event that was possibly or probably related to tacrolimus; the most common were diarrhoea (14.6%), nausea (10.3%), tremor (9.0%), headache (8.7%), abdominal pain (7.9%), dyspepsia (7.6%), increased creatinine (6.8%) and hypertension (5.4%). Twenty-four patients (2.7%) experienced serious adverse events possibly or probably related to study drug; the most common were pneumonia (0.6%), hyperglycaemia (0.3%), gastroenteritis (0.2%), pancreatitis (0.2%) and diabetes mellitus (0.2%). The mean creatinine level increased from 67+/-19 micromol/l (0.76+/-0.22 mg/dl) at baseline to 75+/-26 micromol/l (0.85+/-0.30 mg/dl) (P<0.0001) at end of treatment. 351 (40.3%) of the 872 patients for whom creatinine levels were available at both baseline and during treatment had > or =30% increase from baseline in serum creatinine during the study, either related or unrelated to tacrolimus, with 73 patients (8.4%) having creatinine levels exceeding the normal range. At end of treatment, 177 patients (20.3%) had a > or =30% increase from baseline in creatinine. Serum creatinine remained within the normal range throughout the trial in approximately 90% of patients. At the end of treatment, the ACR20, ACR50 and ACR70 response rates were 38.4%, 18.6% and 9.0% respectively. Over 26% of patients had at least a 70% improvement in both swollen and painful/tender joints. CONCLUSION: This study demonstrates that tacrolimus was safe and well-tolerated and provided clinical benefit over a period of at least 12 months.

Comparative tacrolimus pharmacokinetics: normal versus mildly hepatically impaired subjects.

Tacrolimus (FK506, Prograf), marketed for the prophylaxis of organ rejection following allogenic liver or kidney transplantation, is virtually completely metabolized. The major metabolic pathways are P450 3A4-mediated hydroxylation and demethylation. Since P450 hepatic drug-metabolizing enzymes may be impaired in hepatic dysfunction, a study was conducted to characterize oral and intravenous tacrolimus pharmacokinetics in 6 patients with mild hepatic dysfunction and compared with parameters to those from normal subjects obtained in a separate study. Patients received two treatments: a single 0.020 mg/kg ideal body weight (IBW) i.v. dose infused over 4 hours and approximately 0.12 mg/kg IBW orally; normal subjects were dosed at 0.02 mg/kg 4-hour i.v. and 5 mg (0.065 mg/kg) p.o. Mean blood pharmacokinetic parameters with mild hepatic dysfunction were as follows: clearance = 0.035 L/h/kg, terminal exponential volume of distribution = 2.59 L/kg, terminal exponential half-life = 60.6 hours (i.v.), p.o. maximum blood concentration = 48.2 ng/mL, time of p.o. maximum blood concentration = 1.5 hours, and absolute bioavailability = 22.3%. The respective parameters in normal subjects were as follows: 0.040 L/h/kg, 1.91 L/kg, 34.2 hours (i.v.), 29.7 ng/mL, 1.6 hours, and 17.8%. Inasmuch as clearance and bioavailability were not substantially different from that in normal subjects, patients with mild hepatic impairment may initially be treated with conventional tacrolimus doses, with subsequent dosage adjustments based on response, toxicity, and therapeutic drug monitoring.

Effect of time of meal consumption on bioavailability of a single oral 5 mg tacrolimus dose.

Tacrolimus (FK506, Prograf) is marketed for the prophylaxis of organ rejection following allogenic liver or kidney transplantation. This study investigated the effect of timing of a standardized breakfast meal on both the rate and extent of tacrolimus absorption following a single 5 mg oral dose. The protocol used a randomized, open-label, four-period, four-treatment, four-sequence crossover design in 16 healthy, nonsmoking, drug-free male subjects between the ages of 22 and 45 years who were within 15% of their ideal body weight. The four treatments were the following: (A) fasting for 10 hours, (B) ingestion 1 hour before breakfast, (C) ingestion immediately following consumption of the breakfast, and (D) ingestion 1.5 hours after beginning consumption of the breakfast. The breakfast, which was consumed over 15 minutes, contained 848 kcal, with 30%, 16%, and 54% of calories derived from fat, protein, and carbohydrate, respectively. Tacrolimus absorption in the fasting state provided the greatest relative bioavailability (p < 0.05 compared with all other three treatments). AUC(0-infinity)) averaged 312, 276, 205, and 203 ng x h/mL for treatments A, B, C and D, respectively. In contradistinction to taking the drug 1 hour prior to a meal, which had a relatively minor impact on the relative extent of absorption (approximately 12%) compared to the fasting state, ingestion of tacrolimus immediately after a meal (treatment C) or 1.5 hours subsequent to a meal (treatment D) had a more pronounced influence. Mean AUC(0-infinity) ratios (fasting to either postmeal treatments) were approximately 1.5, indicating that absorption extent was considerably reduced by ingesting tacrolimus capsules immediately after eating or 1.5 hours thereafter. Absorption was also prolonged following drug ingestion after a meal, as indicated by a mean tmax value in the fasting state of 1.84 hours, relative to 3.41 hours (immediately aftermeal, p = 0.0035) and 3.22 hours (1.5 hours postmeal, p = 0.0094). The only discernable difference in parameters between treatments C and D was with Cmax, with values of 7.19 and 9.04 ng/mL, respectively, but was not statistically significantly different (p = 0.231). Based on these results and those from a prior study, it is recommended that under therapeutic conditions, oral tacrolimus be administered in a consistent manner, both with respect to the type of meal as well as timing of ingestion relative to consumption of the meal.

Effect of low- and high-fat meals on tacrolimus absorption following 5 mg single oral doses to healthy human subjects.

Tacrolimus (FK506, Prograf) is a macrolide lactone antibiotic widely used by the oral route for the prophylaxis of organ rejection in patients who have received allogenic liver or kidney transplants. This study investigated the influence of a high- versus a low-fat meal, relative to the fasting state (three treatments total), on the rate and extent of tacrolimus absorption following a single 5 mg oral dose. The protocol employed a three-period, randomized, crossover design employing 5 x 1 mg capsules in 15 healthy male nonsmoking, drug-free volunteers, 20 to 45 years of age, who were within 15% of their ideal body weight. Food had a clinically significant effect in reducing relative bioavailability, as well as slowing absorption, but did not affect terminal exponential half-life (approximately 34 hours). Mean maximum tacrolimus blood concentration (Cmax) values were 25.6, 5.88, and 9.03 ng/mL for the fasting, high-fat, and low-fat treatments, respectively; mean area under the blood concentration-time curve (AUC(0-infinity) values were 272, 181, and 201 (ng/mL)-h, respectively; and mean time of Cmax (tmax) values were 1.37, 6.47, and 3.20 hours, respectively. Differences in parameters between the fasting and each fed treatment were statistically significantly different (p < 0.05). Statistically significant differences also existed in tmax between the two meals. Results also indicated the safety of single 5 mg oral tacrolimus doses administered to healthy volunteers.

Coadministration of tacrolimus and mycophenolate mofetil in stable kidney transplant patients: pharmacokinetics and tolerability.

The tolerance and pharmacokinetics (PK) of tacrolimus (T) by the addition of mycophenolate mofetil (MMF) in stable kidney transplant patients (6/group) on long-term tacrolimus-based therapy were investigated. Patients received combination T and MMF therapy at three MMF doses: 1, 1.5, and 2 g/day administered twice daily. A 12-hour blood PK profile for T was obtained prior to MMF dosing; concomitant 12-hour profiles for T, mycophenolic acid (MPA), and mycophenolic acid glucuronide (MPAG) were obtained after 2 weeks of administration. Tolerance was monitored through 3 months. The intra- and intergroup PK of T were variable. The mean AUC0-12 of T for each group was increased after 2 weeks of concomitant MMF administration, but the increase was not statistically significant. Both drugs were well tolerated. Gastrointestinal events were of interest as such have been attributed to both T and MMF. Events reported were diarrhea, nausea, dyspepsia, and vomiting. Other common adverse events were headache, hypomagnesemia, and tremors. Most were mild, although a few were considered to be moderate. There was no apparent relationship between the incidence of any adverse event and MMF treatment group. In the present study, the coadministration of T and MMF did not significantly alter T pharmacokinetics.

Bioequivalence of 1 and 5 mg tacrolimus capsules using a replicate study design.

Tacrolimus (FK506, Prograf) is marketed for the prophylaxis of organ rejection following allogenic liver or kidney transplantation. A previously conducted, randomized, 24-subject, crossover bioavailability study of 1 and 5 mg capsules (one period each) failed to demonstrate bioequivalence. A single-dose, four-period, four-sequence, randomized, crossover, replicate study (N = 32) was therefore used to evaluate the bioequivalence of the marketed 1 and 5 mg capsules in healthy volunteers. Tacrolimus blood concentrations were measured serially over 72 hours using a commercially available ELISA assay. Noncompartmental pharmacokinetic parameters were determined. Ninety percent CIs of log-transformed parameter ratios were 90.5-101.9, 87.1-101.7, and 89.7-103.8 for Cmax, AUC0-t, and AUC0-infinity, respectively. Since all values were within 80% to 125%, the capsules are bioequivalent. Based on %CVs, intersubject variability was approximately two to three times greater than intrasubject variability. The safety of single 5 mg oral tacrolimus doses administered to healthy volunteers at 7-day intervals was also ascertained.

Dose linearity after oral administration of tacrolimus 1-mg capsules at doses of 3, 7, and 10 mg.

Tacrolimus is an immunosuppressant drug used for the prophylaxis of organ rejection in patients who receive allogenic liver or kidney transplants. This study investigated the relationship between tacrolimus blood concentration-time profiles after 3-, 7-, and 10-mg single oral doses were given to 18 healthy, drug-free, nonsmoking, institutionalized male volunteers. The protocol used a single-dose, 3-period, 3-treatment, nonmasked, randomized-block, complete crossover design. The 90% CIs of the ratios of dose-adjusted, mean, log-transformed values of maximum blood concentration, area under the tacrolimus blood concentration-time curve (0 to the last measurable concentration; lower limit of quantitation = 0.5 ng/mL), and area under the blood concentration-time curve (0 to 0) fell within the range of 125%, indicating dose proportionality for these parameters under experimental conditions. Power to detect a 20% difference for the 3 doses tested was 82.2%, 66.7%, and 72.8%, respectively.

Tacrolimus oral bioavailability doubles with coadministration of ketoconazole.

OBJECTIVE: To quantitate the effect of ketoconazole, an azole antifungal agent and potent inhibitor of CYP3A4 and P-glycoprotein, on the bioavailability of tacrolimus, a substrate of the CYP3A system and of P-glycoprotein. SUBJECTS AND METHODS: The pharmacokinetics of tacrolimus were studied in six healthy volunteers (two women and four men) in a four-dose study after each received single doses of tacrolimus alone (0.1 mg/kg orally and 0.025 mg/kg intravenously) and with coadministered ketoconazole (200 mg orally at bedtime for 12 days). The dose of tacrolimus was reduced during the ketoconazole phase (0.04 mg/kg orally; 0.01 mg/kg intravenously). Ketoconazole and tacrolimus doses were separated by approximately 10 hours. Whole blood tacrolimus concentrations were determined by enzyme-linked immunosorbent assay. Estimated pharmacokinetic parameters in whole blood (mean +/- SD) before and with ketoconazole were calculated with noncompartmental techniques. RESULTS: Coadministration of ketoconazole did not consistently affect tacrolimus clearance (55.6 +/- 16.7 ml/hr/kg versus 42.5 +/- 7.6 ml/hr/kg), and steady-state volume of distribution was unchanged (0.99 +/- 0.26 L/kg versus 0.93 +/- 0.25 L/kg). However, a significant increase in tacrolimus bioavailability (14% +/- 5% versus 30% +/- 8%; p < 0.01) was observed with coadministered ketoconazole. Hepatic bioavailability was unchanged by the presence of ketoconazole (96% +/- 1% versus 97% +/- 1%). CONCLUSIONS: Because ketoconazole did not alter hepatic bioavailability and because 10 hours separated administration times of the drugs, it appears that the marked increase in tacrolimus bioavailability can be explained by ketoconazole having a local inhibitory effect on tacrolimus gut metabolism or on intestinal P-glycoprotein activity.

Plasma concentrations and disposition of clonidine following a constant 14-day epidural infusion in cancer patients.

Epidural administration of clonidine, a partial alpha 2-adrenergic agonist, provides effective relief for patients with intractable cancer pain. However, clonidine's long plasma elimination half-life suggests a potential for plasma accumulation following repeated doses or constant infusion. Adult male and female cancer patients experiencing severe, intractable pain were administered a continuous epidural infusion (30 micrograms/h) of clonidine hydrochloride for 14 days. Plasma clonidine concentrations were determined for 31 patients using a radioimmunoassay with a limit of quantitation of 0.062 ng/mL. Mean (+/- SD) plasma clonidine concentration and calculated total body clearance after 7 days of infusion (respectively, 2.19 +/- 1.17 ng/mL, n = 24; 279 +/- 184 mL/min, n = 27) were comparable to those following 14 days of infusion (2.50 +/- 1.51 ng/mL, n = 19; 272 +/- 163 mL/min, n = 21). Clonidine does not appear to accumulate in the plasma compartment during prolonged (14-day) continuous epidural infusion in cancer patients.

Pharmacokinetics of tacrolimus in liver transplant patients.

OBJECTIVE: To characterize the pharmacokinetics of the immunosuppressive agent tacrolimus (FK 506) in liver transplant patients. METHODS: Patients (n = 16) were assessed during and after 1- to 3-day intravenous infusions followed by a 2-week course of oral dose therapy. Plasma and whole blood data were fitted simultaneously with equations accounting for nonlinear drug binding by red blood cells to generate clearance (CL) and volume of distribution (V). RESULTS: The maximum blood/plasma ratio of tacrolimus was 55.5 +/- 26.8 (SD) and half-life averaged 12.1 +/- 4.7 hours. The CL and V were relatively high based on plasma concentrations (CL, 1.7 L/hr/kg; V, 30 L/kg) and low based on whole blood (CL, 54 ml/hr/kg; V, 0.9 L/kg), with moderate variability (coefficient of variation, 34% to 49%) among the patients. Correlations of plasma CL and V with maximum blood/plasma ratios (ranging from 13 to 114) were strong (r = 0.65 and r = 0.73). Blood binding affects the disposition of tacrolimus, and plasma concentrations are indirectly and inversely related to red cell binding. The oral dose data for tacrolimus yielded a brief absorption lag time (tlag, 0.39 hour), a variable first-order absorption rate constant (ka, 4.5 +/- 3.0 hr-1), and consistent bioavailability (F, 25% +/- 10%). The area under the concentration-time curve versus 12-hour minimum concentration relationships for both whole blood and plasma were nearly linear, confirming the utility of trough values for monitoring drug exposure. CONCLUSION: This study provides pharmacokinetic guidelines for the use of tacrolimus in patients undergoing hepatic transplantation. Nonlinear blood binding is a major source of interpatient variation in the disposition of tacrolimus.

Dopamine-2 receptor blockade does not affect the ocular hypotensive action of timolol.

We have shown that metoclopramide, a dopamine-2 antagonist, failed to antagonise the ocular hypotensive action of timolol. The practical implication of combining dopamine agonists with beta-adrenoceptor antagonists in the treatment of glaucoma is discussed.

Effect of cicloprolol in intraocular pressure in healthy volunteers.

Two oral doses of cicloprolol (50 mg and 100 mg), a beta 1-adrenoceptor partial agonist, were administered to nine healthy volunteers in a double-blind placebo-controlled study. Intraocular pressure (IOP) and exercise heart rate were reduced while the resting heart rate and blood pressure remained unchanged. The responses to the two different doses of cicloprolol were similar.

Stimulation of dopamine receptors (type 2) lowers human intraocular pressure.

The interaction between bromocriptine and metoclopramide on intraocular pressure (IOP), pupil diameter, and other parameters were studied in healthy volunteers. Pupil diameter was not affected by both treatments and only bromocriptine lowered IOP. Prior treatment with metoclopramide blocked the IOP-lowering effect of bromocriptine. It is concluded that bromocriptine lowers IOP by stimulation of dopamine-2 receptors.