| 1. |
- Svensson, Elin M., 1985-, et al.
(författare)
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The Potential for Treatment Shortening With Higher Rifampicin Doses : Relating Drug Exposure to Treatment Response in Patients With Pulmonary Tuberculosis
- 2018
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Ingår i: Clinical Infectious Diseases. - : OXFORD UNIV PRESS INC. - 1058-4838 .- 1537-6591. ; 67:1, s. 34-41
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Tidskriftsartikel (refereegranskat)abstract
- Background. Tuberculosis remains a huge public health problem and the prolonged treatment duration obstructs effective tuberculosis control. Higher rifampicin doses have been associated with better bactericidal activity, but optimal dosing is uncertain. This analysis aimed to characterize the relationship between rifampicin plasma exposure and treatment response over 6 months in a recent study investigating the potential for treatment shortening with high-dose rifampicin. Methods. Data were analyzed from 336 patients with pulmonary tuberculosis (97 with pharmacokinetic data) treated with rifampicin doses of 10, 20, or 35 mg/kg. The response measure was time to stable sputum culture conversion (TSCC). We derived individual exposure metrics with a previously developed population pharmacokinetic model of rifampicin. TSCC was modeled using a parametric time-to-event approach, and a sequential exposure-response analysis was performed. Results. Higher rifampicin exposures increased the probability of early culture conversion. No maximal limit of the effect was detected within the observed range. The expected proportion of patients with stable culture conversion on liquid medium at week 8 was predicted to increase from 39% (95% confidence interval, 37%-41%) to 55% (49%-61%), with the rifampicin area under the curve increasing from 20 to 175 mg/L.h (representative for 10 and 35 mg/kg, respectively). Other predictors of TSCC were baseline bacterial load, proportion of culture results unavailable, and substitution of ethambutol for either moxifloxacin or SQ109. Conclusions. Increasing rifampicin exposure shortened TSCC, and the effect did not plateau, indicating that doses >35 mg/kg could be yet more effective. Optimizing rifampicin dosage while preventing toxicity is a clinical priority.
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| 2. |
- Svensson, Robin J., et al.
(författare)
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A Population Pharmacokinetic Model Incorporating Saturable Pharmacokinetics and Autoinduction for High Rifampicin Doses
- 2018
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Ingår i: Clinical Pharmacology and Therapeutics. - : Wiley. - 0009-9236 .- 1532-6535. ; 103:4, s. 674-683
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Tidskriftsartikel (refereegranskat)abstract
- Accumulating evidence suggests that increasing doses of rifampicin may shorten tuberculosis treatment. The PanACEA HIGHRIF1 trial assessed safety, pharmacokinetics, and antimycobacterial activity of rifampicin at doses up to 40 mg/kg. Eighty-three pulmonary tuberculosis patients received 10, 20, 25, 30, 35, or 40 mg/kg rifampicin daily over 2 weeks, supplemented with standard doses of isoniazid, pyrazinamide, and ethambutol in the second week. This study aimed at characterizing rifampicin pharmacokinetics observed in HIGHRIF1 using nonlinear mixed effects modeling. The final population pharmacokinetic model included an enzyme turnover model accounting for time-dependent elimination due to autoinduction, concentration-dependent clearance, and dose-dependent bioavailability. The relationship between clearance and concentration was characterized by a Michaelis–Menten relationship. The relationship between bioavailability and dose was described using an Emax relationship. The model will be key in determining exposure–response relationships for rifampicin and should be considered when designing future trials and when treating future patients with high-dose rifampicin.
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| 3. |
- Svensson, Robin J., et al.
(författare)
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Greater Early Bactericidal Activity at Higher Rifampicin Doses Revealed by Modeling and Clinical Trial Simulations
- 2018
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Ingår i: Journal of Infectious Diseases. - : Oxford University Press (OUP). - 0022-1899 .- 1537-6613. ; 218:6, s. 991-999
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Tidskriftsartikel (refereegranskat)abstract
- Background. The currently recommended rifampicin dose (10 mg/kg) for treating tuberculosis is suboptimal. The PanACEA HIGHRIF1 trial evaluated the pharmacokinetics and early bactericidal activity of rifampicin doses of up to 40 mg/kg. Conventional statistical analyses revealed no significant exposure-response relationship. Our objectives were to explore the exposure-response relationship for high-dose rifampicin by using pharmacokinetic-pharmacodynamic modeling and to predict the early bactericidal activity of 50 mg/kg rifampicin.Methods. Data included time to Mycobacterium tuberculosis positivity of liquid cultures of sputum specimens from 83 patients with tuberculosis who were treated with 10 mg/kg rifampicin (n = 8; reference arm) or 20, 25, 30, 35, or 40 mg/kg rifampicin (n = 15/arm) for 7 days. We used a semimechanistic time-to-event approach to model the time-to-positivity data. Rifampicin exposure and baseline time to culture positivity were explored as covariates.Results. The baseline time to culture positivity was a significant covariate on the predicted initial bacterial load, and rifampicin exposure was a significant covariate on the bacterial kill rate in sputum resulting in increased early bactericidal activity. The 90% prediction interval for the predicted median day 7 increase in time to positivity for 50 mg/kg rifampicin was 7.25-10.3 days.Conclusions. A significant exposure-response relationship was found between rifampicin exposure and early bactericidal activity. Clinical trial simulations showed greater early bactericidal activity for 50 mg/kg rifampicin.
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| 4. |
- Svensson, Elin, 1985-, et al.
(författare)
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Relative bioavailability of bedaquiline tablets suspended in water : Implications for dosing in children
- 2018
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Ingår i: British Journal of Clinical Pharmacology. - : Wiley. - 0306-5251 .- 1365-2125. ; 84:10, s. 2384-2392
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Bedaquiline is an important novel drug for treatment of multidrug-resistant tuberculosis, but no paediatric formulation is yet available. This work aimed to explore the possibility of using the existing tablet formulation in children by evaluating the relative bioavailability, short-term safety, acceptability and palatability of suspended bedaquiline tablets compared to whole tablets.Methods: A randomized, open-label, two-period cross-over study was conducted in 24 healthy adult volunteers. Rich pharmacokinetic sampling over 48h was conducted at two occasions 14days apart in each participant after administration of 400mg bedaquiline (whole or suspended in water). The pharmacokinetic data were analysed with nonlinear mixed-effects modelling. A questionnaire was used to assess palatability and acceptability.Results: There was no statistically significant difference in the bioavailability of the suspended bedaquiline tables compared to whole. The nonparametric 95% confidence interval of the relative bioavailability of suspended bedaquiline tablets was 94-108% of that of whole bedaquiline tablets; hence, the predefined bioequivalence criteria were fulfilled. There were no Grade 3 or 4 or serious treatment emergent adverse events recorded in the study and no apparent differences between whole tablets and suspension regarding taste, texture or smell.Conclusions: The bioavailability of bedaquiline tablets suspended in water was the same as for tablets swallowed whole and the suspension was well tolerated. This suggests that the currently available bedaquiline formulation could be used to treat multidrug-resistant tuberculosis in children, to bridge the gap between when paediatric dosing regimens have been established and when a paediatric dispersible formulation is routinely available.
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