Induced human cholera

Adsorption and Release of Sulfamethizole from Mesoporous Silica Nanoparticles Functionalised with Triethylenetetramine

Mesoporous silica nanoparticles (MSN) were synthesised and functionalised with triethylenetetramine (MSN-TETA). The samples were fully characterised (transmission electron microscopy, small angle X-ray scattering, Fourier transform infrared spectroscopy, thermogravimetric analysis, zeta potential and nitrogen adsorption/desorption isotherms) and used as carriers for the adsorption of the antimicrobial drug sulphamethizole (SMZ). SMZ loading, quantified by UV-Vis spectroscopy, was higher on MSN-TETA (345.8 mg g-1) compared with bare MSN (215.4 mg g-1) even in the presence of a lower surface area (671 vs. 942 m2 g-1). The kinetics of SMZ adsorption on MSN and MSN-TETA followed a pseudo-second-order model. The adsorption isotherm is described better by a Langmuir model rather than a Temkin or Freundlich model. Release kinetics showed a burst release of SMZ from bare MSN samples (k1 = 136 h-1) in contrast to a slower release found with MSN-TETA (k1 = 3.04 h-1), suggesting attractive intermolecular interactions slow down SMZ release from MSN-TETA. In summary, the MSN surface area did not influence SMZ adsorption and release. On the contrary, the design of an effective drug delivery system must consider the intermolecular interactions between the adsorbent and the adsorbate.

A Physiologically-Based Pharmacokinetic Model of Trimethoprim for MATE1, OCT1, OCT2, and CYP2C8 Drug-Drug-Gene Interaction Predictions

Trimethoprim is a frequently-prescribed antibiotic and therefore likely to be co-administered with other medications, but it is also a potent inhibitor of multidrug and toxin extrusion protein (MATE) and a weak inhibitor of cytochrome P450 (CYP) 2C8. The aim of this work was to develop a physiologically-based pharmacokinetic (PBPK) model of trimethoprim to investigate and predict its drug–drug interactions (DDIs). The model was developed in PK-Sim^®, using a large number of clinical studies (66 plasma concentration–time profiles with 36 corresponding fractions excreted in urine) to describe the trimethoprim pharmacokinetics over the entire published dosing range (40 to 960 mg). The key features of the model include intestinal efflux via P-glycoprotein (P-gp), metabolism by CYP3A4, an unspecific hepatic clearance process, and a renal clearance consisting of glomerular filtration and tubular secretion. The DDI performance of this new model was demonstrated by prediction of DDIs and drug–drug–gene interactions (DDGIs) of trimethoprim with metformin, repaglinide, pioglitazone, and rifampicin, with all predicted DDI and DDGI AUC_last and C_max ratios within 1.5-fold of the clinically-observed values. The model will be freely available in the Open Systems Pharmacology model repository, to support DDI studies during drug development.

Sulfamethoxazole-trimethoprim synergism for Neisseria gonorrhoeae

Sulfamethoxazole and trimethoprim are synergistic against many bacteria in sulfamethoxazole/trimethoprim concentrations of 20:1, but single-dose therapy of gonorrhea with the combination is disappointing. We used agar dilution techniques to determine minimal inhibitory concentrations of sulfamethoxazole and trimethoprim for 168 gonococci isolated from men with acute urethritis in Atlanta, Ga. The geometric mean minimal inhibitory concentrations were 5.6 microgram of sulfamethoxazole per ml and 24.3 microgram of trimethoprim per ml, a ratio of 1:4. The concentration of sulfamethoxazole inhibiting 50% of gonococcal strains dropped only from 4.7 microgram/ml to 2.9 microgram/ml with the addition of a 1/20 dilution of trimethoprim. We studied synergism with various ratios of sulfamethoxazole to trimethoprim against 20 random strains. A ratio of 1:1 was always synergistic and was the most synergistic ratio for 15 strains, whereas the 19:1 ratio was never the most syngergistic. The 19:1 ratio failed to show synergism against seven strains, but showed antagonism at this ratio with five of these seven. The sulfamethoxazole/trimethoprim ratio of 19:1 usually achieved in serum after oral administration is minimally syngergistic and is sometimes antagonistic for gonococci.

Pharmacokinetics and tolerance of a single twelve-tablet dose of trimethoprim (960 mg)-sulfamethoxazole (4,800 mg)

To evaluate the potential usefulness of a single large oral dose of trimethoprim-sulfamethoxazole (TMP-SMZ) for the treatment of uncomplicated genitourinary gonorrhea, the pharmacokinetics of a 12-tablet dose containing 960 mg of TMP and 4,800 mg of SMZ were studied in 15 male volunteers, and the tolerance of this regimen was compared to that of a placebo in a double-blind crossover study. Both TMP and SMZ were rapidly absorbed. Peak mean serum concentrations (+/- standard deviation) of TMP, total SMZ, and free SMZ were 9.2 +/- 2.2, 259.4 +/- 40.9, and 233.7 +/- 33.6 mug/ml, respectively. Elimination half-lives were 16.7, 14.6, and 12.9 h, respectively. When results were compared to data from similar studies after smaller doses, peak mean serum concentrations were proportional to dose, but elimination half-lives were longer after larger doses. Urinary concentrations of TMP, total SMZ, and free SMZ were many-fold higher than serum concentrations. Percents recovery (+/- standard deviation) in urine were 60.6 +/- 10.6, 80.2 +/- 7.8, and 37.4 +/- 6.5%, respectively, during the 48 h after administration. The incidence of severe headache and of objective transient oliguria was significantly higher after TMP-SMZ than after placebo. Although the observed serum concentrations of TMP and SMZ surpassed concentrations necessary to inhibit clinical isolates of Neisseria gonorrhoeae in vitro for longer than 24 h, the adverse reactions associated with a 12-tablet dose of TMP-SMZ would preclude the clinical usefulness of such a therapeutic regimen.