Switching patterns of immediate-release forms of generic mixed amphetamine salts products among privately and publicly insured individuals aged 15-64 years in the United States, 2013-2019.

PURPOSE: Immediate-release forms of generic mixed amphetamine salts (MAS) have been the subject of passive surveillance reports signaling lack of effectiveness. We examined switching patterns that might suggest whether long-term users of specific MAS are more likely to switch away or switch back after use of the MAS of interest in the FDA's Sentinel Distributed Database. METHODS: We required at least 60-day continuous supply of selected MAS grouped by Abbreviated New Drug Application (ANDA) to describe patterns of switching away from and to generics approved under the ANDAs of interest among individuals ages 15-64 years with attention deficit hyperactivity disorder or narcolepsy during 2013-2019. RESULTS: We observed the greatest number of treatment episodes for ANDA 040422 (n = 525 771), followed by ANDA 202424 (n = 181 693), ANDA 040439 (n = 62 363), ANDA 040440 (n = 21 143), and ANDA 040480 (n = 8792). Of those with switches away from their original ANDA, episodes initiated on generic products under ANDA 040422 (48.6%) and ANDA 202424 (43.0%) were most likely to switch back, while those initiated on generic product under ANDA 040480 were least likely (24.1%). Of those episodes with switches to a generic under an ANDA of interest, about one-third (range 27.1% to 37.0%) switched back to the same product. These switches back had a median time to switch of about 30 days. CONCLUSIONS: These descriptive analyses, although subject to limitations, did not suggest increased switching away or switching back after use of the generics of interest. Continued post-marketing surveillance is warranted.

Drug Information Association Pharmacovigilance and Risk Management Strategies 2017: Overview of the Generic Drug Program and Surveillance.

The US Food and Drug Administration's (FDA's) generic drug program has dramatically increased the availability of affordable, high quality generic drugs. The foundation of generic drug approvals is a two-tiered regulatory framework of pharmaceutical equivalence and bioequivalence. Intrinsic to both of these is consideration of the clinical relevance of formulation and bioequivalence data to support an inference of therapeutic equivalence, based on clear evidence that there are no significant differences between the generic drug and the brand name drug. These analyses allow FDA to determine that the generic drug will perform in the patient in the same way, with the same safety and efficacy profiles, as the brand name drug. Allowable differences and the precise definition of what is meant by equivalence are critical to maintaining the quality, efficacy, and safety of generic drugs. The FDA Office of Generic Drugs' (OGD's) Clinical Safety Surveillance Staff (CSSS) has developed investigative processes that complement the broader FDA safety efforts that focus on the potential impact of allowable differences and equivalence determinations for generic drugs. Two recent examples of the CSSS's processes include a clonidine transdermal system and lansoprazole oral disintegrating tablet. Ongoing efforts of the CSSS result in improvements to the FDA's review processes and the quality of generic drugs in the US market.

New Opioid Analgesic Approvals and Outpatient Utilization of Opioid Analgesics in the United States, 1997 through 2015.

BACKGROUND: The opioid epidemic, driven in part by increased prescribing, is a public health emergency. This study examines dispensed prescription patterns and approvals of new opioid analgesic products to investigate whether the introduction of these new drugs increases prescribing. METHODS: Prescribing patterns based on dispensed prescription claims from the U.S. retail setting were assessed with new brand and generic opioid analgesic products approved in the United States from 1997 through 2015. RESULTS: From 1997 through 2015, the U.S. Food and Drug Administration (Silver Spring, Maryland) approved 263 opioid analgesic products, including 33 brand products. Dispensed prescriptions initially increased 80% from 145 million prescriptions in 1997 to a peak of 260 million prescriptions in 2012 before decreasing by 12% to 228 million prescriptions in 2015. Morphine milligram equivalents dispensed per prescription increased from 486 in 1997 to a peak of 950 in 2010, before decreasing to 905 in 2015. In 2015, generic products accounted for 96% (218/228 million prescriptions) of all opioid analgesic prescriptions dispensed. The remaining prescriptions were dispensed for brand products, of which nearly half were dispensed for one brand product (OxyContin, Purdue, USA). CONCLUSIONS: There has been a dramatic increase in prescriptions dispensed for opioid analgesics since 1997 and an increasing number of opioid analgesic approvals; however, the number of prescriptions dispensed has declined since 2012 despite an increasing number of approvals. Examination of dispensed prescriptions shows a shifting and complex market where multiple factors likely influence prescribing; the approval of new products alone may not be sufficient to be a primary driver of increased prescribing. VISUAL ABSTRACT: An online visual overview is available for this article at http://links.lww.com/ALN/B705.

Comparative Risk Assessment of Formulation Changes in Generic Drug Products: A Pharmacology/Toxicology Perspective.

This review highlights general toxicology concerns caused by formulation differences between generic and innovator drugs. It underscores the importance of a scientific, clinically oriented, evidence-based comparative safety evaluation procedure for generic drugs and discusses representative case studies from a pharmacology-toxicology perspective. For consideration by generic drug industry stakeholders, this article provides an overview of comparative risk assessments for generic drug products.

Palmitoylation regulates regulator of G-protein signaling (RGS) 16 function. II. Palmitoylation of a cysteine residue in the RGS box is critical for RGS16 GTPase accelerating activity and regulation of Gi-coupled signalling.

Palmitoylation is a reversible post-translational modification used by cells to regulate protein activity. The regulator of G-protein signaling (RGS) proteins RGS4 and RGS16 share conserved cysteine (Cys) residues that undergo palmitoylation. In the accompanying article (Hiol, A., Davey, P. C., Osterhout, J. L., Waheed, A. A., Fischer, E. R., Chen, C. K., Milligan, G., Druey, K. M., and Jones, T. L. Z. (2003) J. Biol. Chem. 278, 19301-19308), we determined that mutation of NH2-terminal cysteine residues in RGS16 (Cys-2 and Cys-12) reduced GTPase accelerating (GAP) activity toward a 5-hydroxytryptamine (5-HT1A)/G alpha o1 receptor fusion protein in cell membranes. NH2-terminal acylation also permitted palmitoylation of a cysteine residue in the RGS box of RGS16 (Cys-98). Here we investigated the role of internal palmitoylation in RGS16 localization and GAP activity. Mutation of RGS16 Cys-98 or RGS4 Cys-95 to alanine reduced GAP activity on the 5-HT1A/G alpha o1 fusion protein and regulation of adenylyl cyclase inhibition. The C98A mutation had no effect on RGS16 localization or GAP activity toward purified G-protein alpha subunits. Enzymatic palmitoylation of RGS16 resulted in internal palmitoylation on residue Cys-98. Palmitoylated RGS16 or RGS4 WT but not C98A or C95A preincubated with membranes expressing 5-HT1a/G alpha o1 displayed increased GAP activity over time. These results suggest that palmitoylation of a Cys residue in the RGS box is critical for RGS16 and RGS4 GAP activity and their ability to regulate Gi-coupled signaling in mammalian cells.

Palmitoylation regulates regulators of G-protein signaling (RGS) 16 function. I. Mutation of amino-terminal cysteine residues on RGS16 prevents its targeting to lipid rafts and palmitoylation of an internal cysteine residue.

Regulators of G-protein signaling (RGS) proteins down-regulate signaling by heterotrimeric G-proteins by accelerating GTP hydrolysis on the G alpha subunits. Palmitoylation, the reversible addition of palmitate to cysteine residues, occurs on several RGS proteins and is critical for their activity. For RGS16, mutation of Cys-2 and Cys-12 blocks its incorporation of [3H]palmitate and ability to turn-off Gi and Gq signaling and significantly inhibited its GTPase activating protein activity toward aG alpha subunit fused to the 5-hydroxytryptamine receptor 1A, but did not reduce its plasma membrane localization based on cell fractionation studies and immunoelectron microscopy. Palmitoylation can target proteins, including many signaling proteins, to membrane microdomains, called lipid rafts. A subpopulation of endogenous RGS16 in rat liver membranes and overexpressed RGS16 in COS cells, but not the nonpalmitoylated cysteine mutant of RGS16, localized to lipid rafts. However, disruption of lipid rafts by treatment with methyl-beta-cyclodextrin did not decrease the GTPase activating protein activity of RGS16. The lipid raft fractions were enriched in protein acyltransferase activity, and RGS16 incorporated [3H]palmitate into a peptide fragment containing Cys-98, a highly conserved cysteine within the RGS box. These results suggest that the amino-terminal palmitoylation of an RGS protein promotes its lipid raft targeting that allows palmitoylation of a poorly accessible cysteine residue that we show in the accompanying article (Osterhout, J. L., Waheed, A. A., Hiol, A., Ward, R. J., Davey, P. C., Nini, L., Wang, J., Milligan, G., Jones, T. L. Z., and Druey, K. M. (2003) J. Biol. Chem. 278, 19309-19316) was critical for RGS16 and RGS4 GAP activity.

Src-mediated RGS16 tyrosine phosphorylation promotes RGS16 stability.

The amplitude of signaling evoked by stimulation of G protein-coupled receptors may be controlled in part by the GTPase accelerating activity of the regulator of G protein signaling (RGS) proteins. In turn, subcellular targeting, protein-protein interactions, or post-translational modifications such as phosphorylation may shape RGS activity and specificity. We found previously that RGS16 undergoes tyrosine phosphorylation on conserved tyrosine residues in the RGS box. Phosphorylation on Tyr(168) was mediated by the epidermal growth factor receptor (EGFR). We show here that endogenous RGS16 is phosphorylated after epidermal growth factor stimulation of MCF-7 cells. In addition, p60-Src or Lyn kinase phosphorylated recombinant RGS16 in vitro, and RGS16 underwent phosphorylation in the presence of constitutively active Src (Y529F) in EGFR(-) CHO-K1 cells. Blockade of endogenous Src activity by selective inhibitors attenuated RGS16 phosphorylation induced by pervanadate or receptor stimulation. Furthermore, the rate of RGS16 degradation was reduced in cells expressing active Src or treated with pervanadate or a G protein-coupled receptor ligand (CXCL12). Induction of RGS16 tyrosine phosphorylation was associated with increased RGS16 protein levels and enhanced GAP activity in cell membranes. These results suggest that Src mediates RGS16 tyrosine phosphorylation, which may promote RGS16 stability.