Disposition of carumonam (AMA-1080/Ro 17-2301), a new N-sulfonated monocyclic beta-lactam, in rats and dogs

Monobactams: A Unique Natural Scaffold of Four-Membered Ring Skeleton, Recent Development to Clinically Overcome Infections by Multidrug- Resistant Microbes

Background:

Monobactam antibiotics have been testified to demonstrate significant antibacterial activity especially the treatment of infections by superbug microbes. Recently, research has been focused on the structural modifications, and new generation of this privileged natural scaffold.

Objective:

Efforts have been made to discover the structure-antibacterial relationship of monbactams in order to avoid the aimless work involving the ongoing generated analogues. This review aims to summarize the current knowledge and development of monobactams as a broad-spectrum antibacterial scaffolds. The recent structural modifications that expand the activity, especially in the infections by resistant-strains, combinational therapies and dosing, as well as the possibility of crosshypersensitivity/ reactivity/tolerability with penicillins and cephalosporins will also be summarized and inferred. Different approaches will be covered with emphasis on chemical methods and Structure- Activity Relationship (SAR), in addition to the proposed mechanisms of action. Clinical investigation of monobactams tackling various aspects will not be missed in this review.

Conclusion:

The conclusion includes the novels approaches, that could be followed to design new research projects and reduce the pitfalls in the future development of monobactams.

Comparison of the pharmacokinetics and pharmacodynamic profile of carumonam in cystic fibrosis patients and healthy volunteers

Our objectives were to compare the pharmacokinetics (PK) of carumonam, a monobactam, between cystic fibrosis (CF) patients and healthy volunteers and assess its pharmacodynamic profile. We studied 10 adult CF patients and 18 healthy volunteers of similar body size (dose: 2.166 g of carumonam as 15-min intravenous infusion). High performance liquid chromatography with ultraviolet detection (HPLC-UV) was used for drug analysis and NONMEM (ICON, Ellicot City, MD) for population PK and Monte Carlo simulation with targets between > or =20% and 100% free time above MIC (fT > MIC). Unscaled renal clearance was 24% higher in CF patients. Lean body mass and creatinine clearance explained the difference in average clearance and volume of distribution between both subject groups. For a daily dose of 6 g per 70 kg of total body weight, 15-min infusions q8h achieved robust (>90%) probabilities of target attainment (PTAs) (target, 60% fT > MIC) for MICs < or =3 mg/L in CF patients and < or =6 mg/L in healthy volunteers. At the same dose, 4-h infusions q8h achieved robust PTAs up to markedly higher MICs < or =8 to 12 mg/L in CF patients and < or =16 mg/L in healthy volunteers.

In Vitro Assessment of Plasma Protein Binding of 20(R)-Ginsenoside Rh2 by Equilibrium Dialysis and LC-MS Analysis: A Case of Species Differences

20(R)-Ginsenoside Rh2 is isolated from Chinese traditional ginsengs with main antitumor effects. To support its pharmacokinetic study which was essential for the pre-clinical research for new drug development, in this paper, 20(R)-Rh2 plasma protein binding was assessed in vitro at four concentration levels (50, 100, 200, 400 ng/ml) both in rat and human plasma using equilibrium dialysis and followed by LC-MS analysis. The method was optimized against some influencing factors during both experimental procedures. And it was validated to be specific, sensitive, accurate, precise and of satisfactory recovery. The results showed the binding fractions were about 70% for rats and 27% for human within four concentration levels. It exhibited a significant species difference between human and rats for the plasma protein binding of 20(R)-Rh2.

Pharmacokinetics of carumonam (AMA-1080) in patients with impaired renal function and in those undergoing hemodialysis

The pharmacokinetics of carumonam (AMA-1080) were studied after a single intravenous 1.0-g dose was given to 26 subjects grouped according to their renal functions. Creatinine clearance (CLCR) was above 85, 50 to 84, 10 to 49, and below 10 ml/min/1.73 m2 in groups 1, 2, 3, and 4, respectively. All of the six patients in groups 4 were receiving maintenance hemodialysis, and they were studied both during and between hemodialysis sessions. Carumonam obeyed two-compartment model kinetics in all four group. The volume of distribution based on the area under serum concentration-time curve (Varea) did not differ significantly among the four groups, the mean value being 0.309 +/- 0.084 liter/kg. The elimination-phase (beta) half-lives were 1.53 +/- 0.36, 2.00 +/- 0.64, 5.08 +/- 1.85, and 12.8 +/- 4.1 h in groups 1, 2, 3, and 4, respectively. The 0- to 24-h cumulative urinary recoveries of carumonam were 83 +/- 11, 76 +/- 20, 58 +/- 25, and 12 +/- 9% of the administered dose in groups 1, 2, 3, and 4, respectively. The systemic and the renal clearances of carumonam decreased according to the severity of renal dysfunction, and the nonrenal clearance, which was calculated as the difference between renal and systemic clearances also decreased as CLCR decreased. A significant positive correlation existed between beta and CLCR (r = 0.847, P less than 0.01), and the beta of carumonam could be predicted by the following equation: beta (h-1) = 0.00460 X CLCR (ml/min/1.73 m2) + 0.049. Hemodialysis shortened the elimination-phase half-lives from 12.8 +/- 4.1 to 2.66 +/- 1.49 h in the six subjects in group 4. A 5-h hemodialysis in a hypothetical anephric subject weighing 60 kg was estimated to remove 51.4% of the drug present in the body at the start of hemodialysis.

Mechanism of renal excretion of carumonam in rats, rabbits, dogs, and monkeys

The mechanism of the renal excretion of carumonam (CRMN) was investigated in rats, rabbits, dogs, and monkeys. Stop-flow analysis in dogs demonstrated that CRMN is exclusively excreted by glomerular filtration. There was no specific CRMN peak corresponding to the peak of p-aminohippuric acid (PAH) secretion or to the trough of Na+-K+ reabsorption in the stop-flow pattern. Although the PAH peak disappeared when probenecid was administered, the CRMN stop-flow pattern showed no change. In rabbits, however, the CRMN concentration peak corresponding with the PAH peak was detected in the stop-flow pattern; the CRMN peak disappeared when probenecid was administered. The pharmacokinetic parameters in plasma, such as the area under the concentration-time curve, the half-life, and the clearance rate, were affected by probenecid in rats, rabbits, and monkeys, but not in dogs. The results suggest that the renal excretion of CRMN in dogs takes place exclusively through glomerular filtration. In rats, rabbits, and monkeys, however, CRMN is excreted through both glomerular filtration and renal tubular secretion.