Dosing Colistimethate Every 8 h Results in Higher Plasma Concentrations of Active Colistin Than Every 12-Hourly Dosing without Increase in Nephrotoxicity: A Phase 1 Pharmacokinetics Trial in Healthy Adult Volunteers.

Despite its use for decades, pharmacokinetic (PK) and safety studies on colistin are limited. We conducted a phase l, open-label trial to evaluate the safety and PK of multiple doses of intravenous (IV) and aerosolized colistimethate sodium (CMS) administered separately and in combination. In total, 31 healthy adults were enrolled into three cohorts of 9, 10, and 12 participants, respectively. Each cohort received increasing doses of CMS over three dosing periods as follows: Period 1 (IV only), 2.5 mg/kg every 12 h (q12h) to 3.3 mg/kg every 8 h (q8h); Period 2 (aerosolized only), 75 mg 2-4 doses, and Period 3 (combined IV aerosolized), in which was Periods 1 and 2 combined. Safety assessments, serum and lung concentrations of colistin analytes (colistin A, colistin B, CMS A, and CMS B), and kidney biomarkers were measured at specified time points. Increasing the CMS dose from 2.5 mg/kg q12h to q8h resulted in a 33% increase in serum colistin A concentrations from 3.9 µg/mL to 5.3 µg/mL-well above the accepted target of 2 µg/mL for 6 h after dosing, without evidence of nephrotoxicity. However, there was an increase in neurotoxicity, primarily perioral and lingual paresthesias, and self-limited ataxia. IV administration did not increase the lung concentrations of colistin.

A two-part phase 1 study to establish and compare the safety and local tolerability of two nasal formulations of XF-73 for decolonisation of Staphylococcus aureus: A previously investigated 0.5mg/g viscosified gel formulation versus a modified formulation.

OBJECTIVES: Successful decolonisation of nasal Staphylococcus aureus (SA) carriage by mupirocin is limited by increasing drug resistance. This randomised, open-label, phase 1 study compared the safety and local tolerability of two nasal formulations of XF-73, a novel porphyrinic antibacterial with rapid intrinsic activity against SA. METHODS: The study was performed in 60 healthy adults. In Part 1, eight non-SA carriers were randomised to groups of four subjects each and were treated with XF-73 concentrations of 0.5mg/g 2% gel or 2.0mg/g 2% gel. In Part 2, 52 persistent SA carriers were randomised to groups of 13 subjects each and were treated with XF-73 concentrations of 0.5mg/g 2% gel, 2.0mg/g 2% gel, 0.5mg/g 4% gel or 4% viscosified placebo gel. Plasma pharmacokinetic and pharmacodynamic studies were performed. Antistaphylococcal activity was assessed as the presence/absence of SA and by quantification of colonisation using a semiquantitative scale (SA score). RESULTS: 56 subjects (8/8 from Part 1 and 48/52 from Part 2) completed the study, with 47/60 comprising the pharmacokinetic population and 48/60 the pharmacodynamic population. There was no measurable systemic absorption of XF-73. XF-73 treatment was associated with rapid reduction in SA score in all subjects. The most common treatment-emergent adverse events (TEAEs) were rhinorrhoea and nasal dryness (15.5% each in Parts 1 and 2). TEAEs were mild and resolved spontaneously. CONCLUSION: XF-73 was well tolerated with minimal side effects at doses of 0.5mg/g 2% gel and 2.0mg/g 2% gel. These findings support further development of XF-73.

Development and validation of an LC-MS/MS method for the simultaneous determination of bedaquiline and rifabutin in human plasma.

This article describes the simultaneous determination of bedaquiline fumarate (TMC-207) and rifabutin in human plasma by stable isotope dilution tandem mass spectrometry. The methodology was developed for an investigation of potential drug-drug interactions of the two anti-tuberculosis drugs when given together to healthy human volunteers. Use of the two drugs in combination to treat disease caused by Mycobacterium tuberculosis is contemplated as the bacterium becomes resistant to many currently available drugs.

Effects of Rifamycin Coadministration on Bedaquiline Desmethylation in Healthy Adult Volunteers.

There is an urgent need to identify safe and effective combination treatments for multidrug-resistant (MDR) Mycobacterium tuberculosis infection (TB). Bedaquiline, a new diarylquinoline, is approved for the treatment of MDR pulmonary TB in combination with other drugs, which could include rifabutin, which is also used to treat drug-resistant TB. Both rifabutin and bedaquiline are metabolized via cytochrome P450 3A4, and rifabutin is an inducer of this enzyme. Bedaquiline is metabolized into its primary N-monodesmethyl metabolite, M2, and further desmethylated into an N-didesmethyl metabolite, M3. Both metabolites are cytotoxic and induce phospholipidosis. The effect of rifabutin on the generation and disposition of the 2 metabolites was investigated in healthy adult volunteers coadministered bedaquiline and either rifabutin or rifampin. Subjects received single oral doses (400 mg) of bedaquiline on days 1 and 29. Oral rifabutin (300 mg) or rifampin (600 mg) were given daily on days 20-41. In the rifabutin group maximum M2 concentrations (Cmax ) increased significantly (P < .001) from 47.59 to 79.53 ng/mL, and clearance slowed slightly (P = .01). This resulted in significantly (P < .001) increased overall exposure (area under the concentration-time curve [AUC0-τ ]). Peak concentrations of M3 increased approximately 3-fold with little decline thereafter. In rifampin recipients M2 Cmax doubled (48.44 to 101.52 ng/mL), but M2 clearance and time to Cmax significantly (P < .001) increased, and AUC0-∞ and mean residence time significantly decreased (P < .001). Peak M3 concentrations increased 4-fold and rapidly declined. Although both rifamycins accelerate desmethylation of bedaquiline and M2, differences in clearance resulted in sustained elevations of both metabolites during rifabutin, but not rifampin, treatment.

Impact of Rifabutin or Rifampin on Bedaquiline Safety, Tolerability, and Pharmacokinetics Assessed in a Randomized Clinical Trial with Healthy Adult Volunteers.

Bedaquiline is a diarylquinoline that specifically inhibits mycobacterial ATP synthase. Bedaquiline has been used to effectively treat tuberculosis (TB) caused by drug-susceptible and drug-resistant Mycobacterium tuberculosis Rifamycins are a cornerstone of combination drug regimens for the treatment of TB. This phase 1, open-label, randomized, controlled trial evaluated the effect of steady-state dosing of rifabutin or rifampin on the safety, tolerability, and pharmacokinetics of bedaquiline given as a single dose. Thirty-three healthy subjects were enrolled to receive a 400-mg single oral dose of bedaquiline at two time points, on study days 1 and 29. Subjects were randomly assigned to once daily oral doses of rifabutin (300 mg/day, n = 17) or rifampin (600 mg/day, n = 16) during period 2 from days 20 to 41. Serial blood sampling for bedaquiline measurement occurred on days 1 and 29 through 336 h after bedaquiline administration. The day 29 bedaquiline pharmacokinetic parameter estimates were compared to the corresponding day 1 estimates for each rifamycin group. Steady-state rifampin reduced bedaquiline AUC0-336 approximately 45%, from 47.69 h·µg/ml in period 1 to 26.33 h·µg/ml in period 2. Bedaquiline apparent clearance accelerated 24% in rifampin-treated subjects from 6.59 liters/h in period 1 to 8.19 liters/h in period 2. Steady-state rifabutin resulted in little quantitative impact on bedaquiline exposure but was associated with grade 3 and 4 adverse events before and after the day 29 bedaquiline dose. Dosage adjustments may therefore be necessary to ensure that bedaquiline plasma concentrations reach therapeutic levels safely when combining bedaquiline and rifamycins in TB treatment regimens. (This single-site, randomized, open-label, prospective study in healthy adult volunteers was registered at Clinicaltrials.gov under registration no. NCT01341184.).

Developmental neurotoxicity and autism: A potential link between indoor neuroactive pollutants and the curious birth order risk factor.

Epidemiological and demographic studies find an increased risk of autism among first-borns. Toxicological studies show that some semi-volatile substances found in infant products produce adverse effects in neural and endocrine systems of animals, including behavioral and developmental effects. Several factors elevate the exposure of human infants to these chemicals. The highest exposures found in infants are comparable to the exposures that induce neural toxicity in animals. A review of these literatures suggests a linking hypothesis that could bridge the epidemiological and toxicological lines of evidence: an infant's exposure to neuroactive compounds emitted by infant products is increased by product newness and abundance; exposure is likely maximized for first-born children in families that can afford new products. Exposure is reduced for subsequently-born children who reuse these now neuroactive-depleted products. The presence of neuroactive chemical emissions from infant products has implications for birth-order effects and for other curious risk factors in autism, including gender, socioeconomic status, and season-of-birth risk factors.