Pharmacodynamic and pharmacokinetic effects of TPA023, a GABA(A) alpha(2,3) subtype-selective agonist, compared to lorazepam and placebo in healthy volunteers

TPA023, a GABA(A) alpha2,3 alphasubtype-selective partial agonist, is expected to have comparable anxiolytic efficacy as benzodiazepines with reduced sedating effects. The compound lacks efficacy at the alpha1 subtype, which is believed to mediate these effects. This study investigated the effects of 0.5 and 1.5 mg TPA023 and compared them with placebo and lorazepam 2 mg (therapeutic anxiolytic dose). Twelve healthy male volunteers participated in this placebo-controlled, double-blind, double-dummy, four-way, cross-over study. Saccadic eye movements and visual analogue scales (VAS) were used to assess the sedative properties of TPA023. The effects on posturaL stability and cognition were assessed using body sway and a standardized battery of neurophysiological memory tests. Lorazepam caused a significant reduction in saccadic peak velocity, the VAS alertness score and impairment of memory and body sway. TPA023 had significant dose dependent effects on saccadic peak velocity (85 deg/sec maximum reduction at the higher dose) that approximated the effects of lorazepam. In contrast to lorazepam, TPA023 had no detectabLe effects on saccadic latency or inaccuracy. Also unlike lorazepam, TPA023 did not affect VAS alertness, memory or body sway. These results show that the effect profile of TPA023 differs markedly from that of lorazepam, at doses that were equipotent with regard to effects on saccadic peak veLocity. Contrary to lorazepam, TPA023 caused no detectable memory impairment or postural imbalance. These differences reflect the selectivity of TPA023 for different GABA(A) receptor subtypes.

Pharmacokinetics of ertapenem in healthy young volunteers

Ertapenem (INVANZ) is a new once-a-day parenteral beta-lactam antimicrobial shown to be effective as a single agent for treatment of various community-acquired and mixed infections. The single- and multiple-dose pharmacokinetics of ertapenem at doses up to 3 g were examined in healthy young men and women volunteers. Plasma and urine samples collected were analyzed using reversed-phase high-performance liquid chromatography with UV detection. Ertapenem is highly bound to plasma protein. The protein binding changes from approximately 95% bound at concentrations of <50 micro g/ml to approximately 92% bound at concentrations of 150 micro g/ml (concentration at the end of a 30-min infusion following the 1-g dose). The nonlinear protein binding of ertapenem resulted in a slightly less than dose proportional increase in the area under the curve from 0 h to infinity (AUC(0- infinity )) of total ertapenem. The single-dose AUC(0- infinity ) of unbound ertapenem was nearly dose proportional over the dose range of 0.5 to 2 g. The mean concentration of ertapenem in plasma ranged from approximately 145 to 175 micro g/ml at the end of a 30-min infusion, from approximately 30 to 34 micro g/ml at 6 h, and from approximately 9 to 11 micro g/ml at 12 h. The mean plasma t(1/2) ranged from 3.8 to 4.4 h. About 45% of the plasma clearance (CL(P)) was via renal clearance. The remainder of the CL(P) was primarily via the formation of the beta-lactam ring-opened metabolite that was excreted in urine. There were no clinically significant differences between the pharmacokinetics of ertapenem in men and women. Ertapenem does not accumulate after multiple once-daily dosing.

Enalapril in RAPIDISC (wafer formulation): pharmacokinetic evaluation of a novel, convenient formulation

BACKGROUND

Enalapril in RAPIDISC* (wafer), a new easy-to-administer formulation of enalapril, may improve the convenience of enalapril therapy, thereby helping patients adhere to antihypertensive treatment.

SUBJECTS AND METHODS

To determine whether 20 mg enalapril wafer is bioequivalent to the conventional 20 mg enalapril tablet, an open-label, two-period crossover study was performed in 16 healthy male volunteers. Cumulative urinary recovery of free enalaprilat (active metabolite of enalapril) and the serum maximum concentration of free enalaprilat (Cmax) were the primary pharmacokinetic parameters used to determine bioequivalence in this study. Bioequivalence was defined as the geometric mean ratio (wafer: tablet) falling within the equivalence limits of 0.80 to 1.25 for both parameters.

RESULTS

Cumulative urinary recovery of free enalaprilat (0 - 72 hours) was similar between the wafer and conventional tablet formulations (arithmetic mean 5.13 vs. 5.03 mg, about 36% of dose). The geometric mean ratio of the urinary recovery of free enalaprilat (wafer: tablet) was 1.03 (90% CI: 0.93, 1.15). Cmax of serum enalaprilat was also similar between the wafer and conventional tablet formulations (arithmetic mean 85.7 vs. 76.3 ng/ml). The geometric mean Cmax ratio (wafer: tablet) was 1. 10 (90% CI: 1.00, 1.22). Both enalapril formulations were well tolerated.

CONCLUSION

This study demonstrates that 20 mg enalapril in RAPIDISC is bioequivalent to 20 mg enalapril conventional tablet.

Single-dose pharmacokinetics of indinavir and the effect of food

Indinavir sulfate is a human immunodeficiency virus type 1 (HIV-1) protease inhibitor indicated for treatment of HIV infection and AIDS in adults. The purpose of this report is to summarize single-dose studies which characterized the pharmacokinetics of the drug and the effect of food in healthy volunteers. Indinavir concentrations in plasma and urine were obtained by high-pressure liquid chromatography and UV detection assay methods. The results indicate that indinavir was rapidly absorbed in the fasting state, with the time to the maximum concentration in plasma occurring at approximately 0.8 h for all doses studied. Over the 40- to 1,000-mg dose range studied, concentrations in plasma and urinary excretion of unchanged drug increased greater than dose proportionally. The nonlinear pharmacokinetics were attributed to the dose-dependent oxidative metabolism of first-pass metabolism as well as to metabolism in the systemic circulation. Renal clearance slightly exceeded the glomerular filtration rate, suggesting a net tubular secretion component. At high concentrations in plasma, tubular secretion appeared to be lowered because there was a trend for a decreased renal clearance. Administration of 400 mg of indinavir sulfate following a high-fat breakfast resulted in a blunted and decreased absorption (areas under the concentration-time curves [AUCs], 6.86 microM.h in the fasted state versus 1.54 microM.h in the fed state; n = 10). However, two types of low-fat meals were found to have no significant effect on the absorption of 800 mg of indinavir sulfate (AUCs, 23.15 microM.h in the fasted state versus 22.71 and 21.36 microM.h, respectively, in the fed state; n = 11). Immediately following dosing, the concentrations of indinavir in urine often exceeded its intrinsic solubility. To reduce the risk of nephrolithiasis, it is recommended that indinavir sulfate be administered with water.

Expanded clinical evaluation of lovastatin (EXCEL) study results: III. Efficacy in modifying lipoproteins and implications for managing patients with moderate hypercholesterolemia

In the multicenter, double-blind EXCEL (Expanded Clinical Evaluation of Lovastatin) study the efficacy of lovastatin in modifying plasma lipids and lipoproteins in 8,245 participants with moderate primary hypercholesterolemia was evaluated. Patients were randomly assigned to 48 weeks of treatment with diet and placebo or diet and lovastatin 20 or 40 mg once a day, or 20 or 40 mg twice a day. At all of these dosages, lovastatin produced substantial dose-dependent reductions in low-density-lipoprotein (LDL)-cholesterol levels, averaging 24% (20 mg/day) to 40% (80 mg/day). The magnitude of the effect of this lipoprotein was further reflected by the percentage of patients who achieved National Cholesterol Education Program (NCEP) goals. In the absence of coronary artery disease (CAD) or two other CAD risk factors, the LDL-cholesterol goal of 4.14 mmol/L (160 mg/dL) was attained by 22% of patients in the placebo group and between 81% (20 mg/day) and 96% (80 mg/day) of those treated with lovastatin. For those with CAD or at least two other CAD risk factors, the LDL-cholesterol goal of 3.36 mmol/L (130 mg/dL) was attained by 4% of placebo patients and between 38% (20 mg/day) and 83% (80 mg/day) of those treated with lovastatin. Lovastatin also increased high-density-lipoprotein cholesterol (7-10%) and decreased triglycerides (10-19%) in a dose-dependent manner. Thus, when used as an adjunct to a prudent diet, lovastatin produces favorable changes in the entire lipoprotein profile and is a highly effective agent for managing patients with primary hypercholesterolemia.

Expanded Clinical Evaluation of Lovastatin (EXCEL) study results. I. Efficacy in modifying plasma lipoproteins and adverse event profile in 8245 patients with moderate hypercholesterolemia

In the Expanded Clinical Evaluation of Lovastatin (EXCEL) Study, a multicenter, double-blind, diet- and placebo-controlled trial, we evaluated the efficacy and safety of lovastatin in 8245 patients with moderate hypercholesterolemia. Patients were randomly assigned to receive placebo or lovastatin at a dosage of 20 mg once daily, 40 mg once daily, 20 mg twice daily, or 40 mg twice daily for 48 weeks. Lovastatin produced sustained, dose-related (P less than .001) changes as follows (for dosages of 20 to 80 mg/d): decreased low-density lipoprotein-cholesterol level (24% to 40%), increased high-density lipoprotein-cholesterol level (6.6% to 9.5%), decreased total cholesterol level (17% to 29%), and decreased triglyceride level (10% to 19%). The National Cholesterol Education Program's low-density lipoprotein-cholesterol level goal of less than 4.14 mmol/L (160 mg/dL) was achieved by 80% to 96% of patients, while the less than 3.36 mmol/L (130 mg/dL) goal was achieved by 38% to 83% of patients. The difference between lovastatin and placebo in the incidence of clinical adverse experiences requiring discontinuation was small, ranging from 1.2% at 20 mg twice daily to 1.9% at 80 mg/d. Successive transaminase level elevations greater than three times the upper limit of normal were observed in 0.1% of patients receiving placebo and 20 mg/d of lovastatin, increasing to 0.9% in those receiving 40 mg/d and 1.5% in those receiving 80 mg/d of lovastatin (P less than .001 for trend). Myopathy, defined as muscle symptoms with a creatine kinase elevation greater than 10 times the upper limit of normal, was found in only one patient (0.1%) receiving 40 mg once daily and four patients (0.2%) receiving 80 mg/d of lovastatin. Thus, lovastatin, when added after an adequate trial of a prudent diet, is a highly effective and generally well-tolerated treatment for patients with moderate hypercholesterolemia.

Expanded clinical evaluation of lovastatin (EXCEL) study: design and patient characteristics of a double-blind, placebo-controlled study in patients with moderate hypercholesterolemia

The randomized, double-blind, placebo-controlled trial described in this report was undertaken to clarify the dose-response relation of lovastatin therapy to lipid-modifying efficacy (lipid/lipoprotein modification) and drug-related adverse events in a population with moderately elevated fasting plasma total cholesterol (240 to 300 mg/dl) and low-density lipoprotein cholesterol (greater than or equal to 160 mg/dl). Men or women (postmenopausal or surgically sterile), aged 18 to 70 years, were entered into the trial with minimal exclusion criteria. After 4 to 6 weeks of an American Heart Association phase I diet or a more stringent diet, 8,245 patients from 362 sites were randomized to 1 of 5 parallel diet and drug treatment groups: placebo (n = 1,663) or lovastatin, 20 mg (n = 1,642) and 40 mg (n = 1,645) with the evening meal, and 20 mg (n = 1,646) or 40 mg twice daily (n = 1,649). The regimen of diet and lovastatin (or placebo) was followed for 48 weeks. The 5 treatment groups were similar at baseline. The total cohort had the following characteristics: 59% were men (mean age 56 years); 92% were white; 59% had completed at least 1 year of education beyond high school; 57% had a history of cardiovascular and associated disease; 40% had a history of hypertension; and 29% had coronary artery disease. Health habits were similar among groups, with 18% of patients reporting cigarette smoking, 14% reporting that they consume greater than 1 alcoholic beverage daily and 67% reporting no strenous exercise. Mean lipid/lipoprotein levels were also similar among groups, with the following average levels: total cholesterol (258 mg/dl), low-density lipoprotein cholesterol (180 mg/dl), high-density lipoprotein cholesterol (45 mg/dl) and triglycerides (median = 155 mg/dl). The large size of this trial, its placebo-controlled, double-blind design and the similarity of treatment groups at baseline should allow clear documentation of the long-term effects of lovastatin treatment and generalization of the results to a substantial portion of patients who may be candidates for lipid-modifying therapy.

Norfloxacin versus trimethoprim-sulfamethoxazole in the treatment of urinary tract infections

In a controlled, randomized trial of 133 patients with proven urinary tract infections (UTIs), significantly more pathogens were found to be susceptible to norfloxacin than to trimethoprim-sulfamethoxazole (TMP-SMZ) (p less than 0.01). Among patients with pathogens susceptible to both drugs, more of those treated with norfloxacin were cured or improved (p = 0.06). When at least one patient variable, i.e., prior history of therapy, was corrected for, this difference became significant (p = 0.03). Norfloxacin eradicated 11 of 13 infections due to Pseudomonas aeruginosa and 6 of 7 due to enterococci. Five patients treated with norfloxacin and two treated with TMP-SMZ had relapses within 6 weeks. Significantly fewer adverse experiences occurred in patients receiving norfloxacin (p less than 0.01).

A multiclinic randomized study of the comparative efficacy, safety and tolerance of imipenem/cilastatin and moxalactam

The efficacy, safety and tolerance of imipenem/cilastatin and moxalactam were compared in a randomized trial in the United States involving 19 centers and 441 patients. Significantly more organisms were susceptible to imipenem than moxalactam. Although the bacteriological outcomes were similar, the clinical outcome was significantly better in the imipenem/cilastatin treatment group. The incidence of colonization and superinfection was similar in both groups. Moxalactam was less irritating at the site of injection than imipenem/cilastatin. The safety profiles were similar except for bleeding episodes in the moxalactam group.