PubMed · 14601290
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N Warhaft. 2003. Naltrexone implants.. https://pubmed.ncbi.nlm.nih.gov/14601290/
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An alternative to detoxification by oral therapy with the narcotic antagonist naltrexone is the subcutaneous implantation of naltrexone pellets. From detoxified patients with naltrexone implants (1g) 26 blood samples were collected up to 73 days after implantation. The assay for naltrexone and 6-beta-naltrexol in plasma was developed using automated mixed-mode solid-phase extraction, catalysed trimethylsilylation and gas chromatography-mass spectrometry in single ion monitoring mode with naloxone as internal standard. The analytical method was very sensitive with limits of detection of 0.1 ng/ml and was linear up to 60 ng/ml for naltrexone and 200 ng/ml for naltrexol. Intra-day precision for naltrexone and naltrexol were 24.3 and 22.9%, respectively, at the LLOQ (accuracy 1.4 and 0.4%, respectively) and less than 10% (2.0, 6.0 and 20.0 ng/ml, n = 6 each) above. Inter-day precision was 7.9% (accuracy -0.6%) for naltrexone and 10.9% (accuracy 1.6%) for naltrexol (20 ng/ml, n = 10). Extraction recoveries were 83% for both analytes (10 ng/ml, n = 6). The concentrations of naltrexone and naltrexol in the plasma samples were in the range of 0.7-13.7 and 0.9-17.0 ng/ml, respectively. The simple analytical procedure described provided good sensitivity for the assay of naltrexone and naltrexol in plasma after naltrexone pellet implantation.
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This paper describes the design and evaluation of an early stage drug release apparatus (ERA) to determine drug release from pellets at times less than 1 min. The apparatus comprises a stirred sample chamber in which the sample is retained by a BS150 mesh screen (0.106 mm), and a series of jacketed cups containing the medium (80 ml) which are raised and lowered in turn over the fixed sample chamber for specified periods. Three types of early release studies were used: single 60s study (single cup), 10s followed by 50s (two cups) and 10, 20, 30...60s multiple changeover differential release (six cups). The effects of stirrer speed, stirrer position and multiple changeover on drug release from standard paracetamol-alginate pellets were investigated. Drug release rates from non-disintegrating pellets were reproducibly determined. The three types of early release study schemes yielded reproducible drug release data over sampling times less than 1 min. Stirrer speed, and depth, and changeover motion of release cups affected drug release but yielded reproducible results. Release from the standard pellets used to study the apparatus took 3 days to stabilize and remained stable thereafter. The apparatus can be used for screening of pellet formulations of sparingly soluble drugs during their developmental stage and regular quality assurance studies of pellets (>150 mesh size). Along with early release studies of pellets, it could be easily modified to study other types of formulations and for automation.