Higher methadone dose at time of release from prison predicts linkage to maintenance treatment for people with HIV and opioid use disorder transitioning to the community in Malaysia

BACKGROUND

Incarcerated people with HIV and opioid-dependence often experience poor post-release outcomes in the absence of methadone maintenance treatment (MMT). In a prospective trial, we assessed the impact of methadone dose achieved within prison on linkage to MMT after release.

METHODS

From 2010 to 2014, men with HIV (N = 212) and opioid dependence before incarceration were enrolled in MMT within 6 months of release from Malaysia's largest prison and followed for 12-months post-release. As a prospective trial, allocation to MMT was at random and later by preference design (predictive nonetheless). MMT dosing was individually targeted to minimally achieve 80 mg/day. Time-to-event analyses were conducted to model linkage to MMT after release.

FINDINGS

Of the 212 participants allocated to MMT, 98 (46 %) were prescribed higher dosages (≥80 mg/day) before release. Linkage to MMT after release occurred in 77 (36 %) participants and significantly higher for those prescribed higher dosages (46% vs 28 %; p = 0.011). Factors associated with higher MMT dosages were being married, on antiretroviral therapy, longer incarceration periods, having higher levels of depression, and methadone preference compared to randomization. After controlling for other variables, being prescribed higher methadone dosage (aHR: 2.53, 95 %CI: 1.42-4.49) was the only independent predictor of linkage to methadone after release.

INTERPRETATION

Higher doses of methadone prescribed before release increased the likelihood of linkage to MMT after release. Methadone dosing should be introduced into international guidelines for treatment of opioid use disorder in prisons and further post-release benefits should be explored.

FUNDING

National Institute of Drug Abuse (NIDA).

Computing optimal drug dosing with OptiDose: implementation in NONMEM

Determining a drug dosing recommendation with a PKPD model can be a laborious and complex task. Recently, an optimal dosing algorithm (OptiDose) was developed to compute the optimal doses for any pharmacometrics/PKPD model for a given dosing scenario. In the present work, we reformulate the underlying optimal control problem and elaborate how to solve it with standard commands in the software NONMEM. To demonstrate the potential of the OptiDose implementation in NONMEM, four relevant but substantially different optimal dosing tasks are solved. In addition, the impact of different dosing scenarios as well as the choice of the therapeutic goal on the computed optimal doses are discussed.

Evaluation of the pharmacokinetic drug-drug interaction potential of iohexol, a renal filtration marker

PURPOSE

Carboplatin dose is calculated based on kidney function, commonly estimated with imperfect creatinine-based formulae. Iohexol is used to measure glomerular filtration rate (GFR) and allows calculation of a more appropriate carboplatin dose. To address potential concerns that iohexol administered during a course of chemotherapy impacts that therapy, we performed in vitro and in vivo pharmacokinetic drug-drug interaction evaluations of iohexol.

METHODS

Carboplatin was administered IV to female mice at 60 mg/kg with or without iohexol at 300 mg/kg. Plasma ultrafiltrate, kidney and bone marrow platinum was quantitated by atomic absorption spectrophotometry. Paclitaxel microsomal and gemcitabine cytosolic metabolism as well as metabolism of CYP and UGT probes was assessed with and without iohexol at 300 µg/mL by LC-MS/MS.

RESULTS

In vivo carboplatin exposure was not significantly affected by iohexol co-administration (platinum AUC combination vs alone: plasma ultrafiltrate 1,791 vs 1920 µg/mL min; kidney 8367 vs 9757 µg/g min; bone marrow 12.7 vs 12.7 µg/mg-protein min). Paclitaxel microsomal metabolism was not impacted (combination vs alone: 6-α-OH-paclitaxel 38.3 versus 39.4 ng/mL/60 min; 3-p-OH-paclitaxel 26.2 versus 27.7 ng/mL/60 min). Gemcitabine human cytosolic elimination was not impacted (AUC combination vs gemcitabine alone: dFdU 24.1 versus 23.7 µg/mL/30 min). Iohexol displayed no relevant inhibition of the CYP and UGT enzymes in human liver microsomes.

CONCLUSIONS

Iohexol is unlikely to affect the clinical pharmacokinetics of carboplatin, paclitaxel, gemcitabine, or other agents used in combination with carboplatin treatment. Measuring GFR with iohexol to better dose carboplatin is unlikely to alter the safety or efficacy of chemotherapy through pharmacokinetic drug-drug interactions.

What the Clinical Microbiologist Should Know About Pharmacokinetics/Pharmacodynamics in the Era of Emerging Multidrug Resistance: Focusing on β-Lactam/β-Lactamase Inhibitor Combinations

As a class, β-lactamase inhibitors have proved successful in extending the clinical utility of β-lactam antibiotics by circumventing β-lactamase-mediated resistance. However, the rapid evolution of these β-lactamases calls for a critical reevaluation of the relationships between susceptibility, drug exposures, and bacterial response. The existing paradigm for in vitro susceptibility testing and development of β-lactam/β-lactamase inhibitor combinations may not optimally facilitate clinical use. Thus, alternative approaches for pairing these combinations and evaluating in vitro susceptibility are needed to provide better guidance to clinicians.