Characterization of Pharmacogenetic Information in Food and Drug Administration Drug Labeling and the Table of Pharmacogenetic Associations.

BACKGROUND: The US Food and Drug Administration (FDA) recommends using only FDA-reviewed pharmacogenetic information to make prescribing decisions based on genetic test results. Such information is available in drug labeling and in the Table of Pharmacogenetic Associations ("Associations table"). OBJECTIVE: To compile a list of drug-gene pairs from drug labeling and the Associations table and categorize the pharmacogenetic information and clinical outcome associated with each drug-gene pair. METHODS: This was a cross-sectional analysis of pharmacogenetic information in the Associations table and individual drug labeling in March 2020. We used the Table of Pharmacogenomic Biomarkers in Drug Labeling to identify drug labels to review. We categorized the pharmacogenetic information for each drug-gene pair according to whether the purpose was to describe (1) polymorphisms affecting drug disposition (metabolism or transport), (2) polymorphisms affecting a direct drug target, (3) variants associated with adverse drug reaction (ADR) susceptibility, (4) variants associated with therapeutic failure, (5) a biomarker-defined indication, or (6) a biomarker-defined ADR. We also categorized the clinical outcome-efficacy, safety, or unknown-associated with each drug-gene pair. We reported counts and proportions of drug-gene pairs in each pharmacogenetic information and clinical outcome category. RESULTS: We identified 308 drug-gene pairs, of which 36% were associated with a biomarker-defined drug indication, 33% with polymorphic drug metabolism, and 28% with ADR susceptibility. Most drug-gene pairs (n = 267, 87%) were associated with an efficacy or safety-related outcome. CONCLUSION AND RELEVANCE: FDA-reviewed pharmacogenetic information is available for more than 300 drug-gene pairs and can help guide prescribing decisions.

Black box warning contraindicated comedications: concordance among three major drug interaction screening programs.

BACKGROUND: Black box warnings represent the strongest safety warning that the Food and Drug Administration can issue for a marketed prescription drug. Some black box warnings recommend against coadministration of specific medications due to an increased risk for serious, perhaps life-threatening, effects. OBJECTIVE: To determine the level of agreement in presence, clinical severity scores level of documentation ratings, and alert content among 3 leading drug interaction screening programs with regard to contraindicated comedications that are mentioned in black box warnings. METHODS: We reviewed the prescribing information for currently marketed prescription drugs with a black box warning that mentioned a contraindicated drug combination. We selected the drug interaction databases Facts & Comparisons 4.0, MICROMEDEX DRUG-REAX, and Lexi-Comp Lexi-Interact to evaluate the interactions. Discrepancies in the inclusion of interactions and level of agreement in clinical severity scores and level of documentation ratings for each interaction were assessed, using descriptive statistics, Spearman's correlation coefficient, Kendall-Stuart tau-c, and Cronbach's alpha. RESULTS: We identified 11 drugs with black box warnings that contained information on 59 unique contraindicated drug combinations, only 68% of which were covered by any source. Lexi-Comp detected the most interactions (n = 29) and DRUG-REAX the least (n = 18). Only 3 drug combinations were detected and rated as contraindicated or potentially life-threatening in all 3 databases. The severity scores and level of documentation ratings varied widely. CONCLUSIONS: There are discrepancies among major drug interaction screening programs in the inclusion, severity, and level of documentation of contraindicated drug combinations mentioned in black box warnings. Further studies could explore the implications of these inconsistencies, particularly with regard to the integration of black box warning information in clinical practice. Clinicians should consult multiple drug resources to maximize the potential for detecting a potentially severe drug interaction.

A review of three stand-alone topical thrombins for surgical hemostasis.

BACKGROUND: Topical thrombins are active hemostatic agents that can be used to minimize blood loss during surgery. Before 2007, the only topical thrombins available were derived from bovine plasma. Antibody formation to bovine thrombin and/or factor V, with subsequent risk of cross-reactivity with human factor V, and hemorrhagic complications associated with human factor-V deficiencies have been described in case reports of surgeries in which bovine thrombins were used. This risk is now included in the boxed warning section of the bovine thrombin prescribing information. In 2007 and 2008, 2 new topical thrombins from nonbovine sources received approval for use from the US Food and Drug Administration. The 3 active topical thrombins that are currently marketed are bovine plasma-derived thrombin, human plasma-derived thrombin, and human recombinant thrombin. OBJECTIVE: The purpose of this review was to evaluate the literature on the efficacy and safety of topical thrombins and discuss the pharmacoeconomic considerations associated with their use. METHODS: PubMed, EMBASE, and International Pharmaceutical Abstracts were searched for relevant papers published in English through October 10,2008, using the terms thrombin, human recombinant thrombin, bovine thrombin, plasma derived thrombin, and topical thrombin. Manufacturer-provided materials were also reviewed. Abstracts and unpublished data, as well as evaluations of sealants, adhesives, glues, and other hemostats that contain thrombin mixed with fibrinogen and other clotting factors, were excluded. RESULTS: Four randomized, double-blind studies involving the active, stand-alone topical thrombins were found. The bovine thrombin involved in these studies was the predecessor to the currently marketed, highly purified bovine formulation. No studies comparing the human products, studies involving the highly purified bovine preparation, or placebo-controlled studies involving bovine thrombin were found. In a Phase III comparison of human recombinant thrombin and bovine thrombin, the percentages of patients who achieved hemostasis within 10 minutes of topical thrombin application were 95.4% and 95.1%, respectively (95% CI, -3.7 to 5.0). The incidence of hemostasis within 10 minutes was also similar in a Phase III comparison of human plasma-derived thrombin and bovine thrombin (both, 97.4% [95% CI, 0.96 to 1.05]). In the study that compared human recombinant and bovine thrombin, the incidence of antiproduct antibody formation was 21.5% (43/200) in the bovine thrombin group and 1.5% (3/198) in the human recombinant thrombin group (P < 0.001); patients with antibodies to bovine thrombin had numerically higher incidences of bleeding or thromboembolic events than did patients without these antibodies (19% vs 13%; P value not reported). Human plasma-derived thrombin is available as a frozen sterile solution that must be thawed before application, whereas the human recombinant and bovine plasma-derived products are supplied as unrefrigerated sterile powders that must be reconstituted before use. The human thrombins are more costly than bovine thrombin on a per-vial basis. The average wholesale prices (US $, 2008) for 5000-IU vials of bovine thrombin and human recombinant thrombin were $87.85 and $103.20, respectively; the average wholesale price for a 4000- to 6000-IU vial of human plasma-derived thrombin was $96.00. CONCLUSIONS: Topical thrombins vary in the ways in which they are manufactured and their safety profiles, storage requirements, and costs. Human recombinant thrombin and human plasma-derived thrombin have each been shown to have hemostatic efficacy comparable to that of bovine thrombin. Bovine thrombin carries the risk of formation of cross-reactive antibodies to bovine thrombin, factor V, and other impurities that may be present in these formulations. Immunogenicity data for the currently marketed, highly purified bovine thrombin relative to older formulations of bovine thrombin could not be found. Whether the potential safety advantage justifies the added cost of the human products remains to be established.

Using drug knowledgebase information to distinguish between look-alike-sound-alike drugs.

Objective: To extract drug indications from a commercial drug knowledgebase and determine to what extent drug indications can discriminate between look-alike-sound-alike (LASA) drugs. Methods: We extracted drug indications disease concepts from the MedKnowledge Indications module from First Databank Inc. (South San Francisco, CA) and associated them with drugs on the Institute for Safe Medication Practices (ISMP) list of commonly confused drug names. We used high-level concepts (rather than granular concepts) to represent the general indications for each drug. Two pharmacists reviewed each drug's association with its high-level indications concepts for accuracy and clinical relevance. We compared the high-level indications for each commonly confused drug pair and categorized each pair as having a complete overlap, partial overlap or no overlap in high-level indications. Results: Of 278 LASA drug pairs, 165 (59%) had no overlap and 58 (21%) had partial overlap in high-level indications. Fifty-five pairs (20%) had complete overlap in high-level indications; nearly half of these were comprised of drugs with the same active ingredient and route of administration (e.g., Adderall, Adderall XR). Conclusions: Drug indications data from a drug knowledgebase can discriminate between many LASA drugs.

Bevacizumab for neovascular ocular diseases.

OBJECTIVE: To review the efficacy and safety of off-label use of bevacizumab for neovascular ocular diseases. DATA SOURCES: A PubMed (1966-January 2007) search was conducted using the terms human, intravitreal, bevacizumab, macular, and retinopathy. Meeting abstracts from the American Academy of Ophthalmology, Retina Society, Macula Society, and Association for Research in Vision and Ophthalmology were reviewed. STUDY SELECTION AND DATA EXTRACTION: Controlled studies, unpublished reports involving 100 or more subjects, and published reports describing 5 or more subjects were reviewed. Only English-language articles were considered. DATA SYNTHESIS: Intravitreal bevacizumab has been evaluated in 133 patients in unpublished controlled studies. Over 3500 patients have been evaluated in open-label studies with duration of follow-up ranging from 3 months to 1 year. The most common use was neovascular age-related macular degeneration (AMD). Other conditions studied included diabetic retinopathy, pathological myopia, neovascular glaucoma, and macular edema due to diabetes, retinal vein occlusion, or uveitis. Statistically significant improvements in visual acuity, as well as decreases in retinal thickness and the extent of choroidal neovascularization, were noted. Intravitreal bevacizumab was well tolerated over the short term. In a registry compiling adverse experiences of 7113 intravitreal injections, rates of adverse events were less than or equal to 0.21%. CONCLUSIONS: Uncontrolled studies support a benefit of intravitreal bevacizumab in neovascular AMD for 3 months to 1 year. Low cost is a significant advantage of bevacizumab. Patients should discuss the potential risks and benefits of intravitreal bevacizumab and other available therapies with their physicians before receiving treatment. Controlled trials are needed to characterize the safety and efficacy of intravitreal bevacizumab and determine the optimal treatment regimen.

Unlabeled uses of botulinum toxins: a review, part 1.

PURPOSE: Efficacy and safety data regarding the unlabeled uses of botulinum toxins are reviewed, and the pharmacology, adverse effects, and characteristics of commercially available botulinum toxins are discussed. SUMMARY: More than 300 articles have been published on the use of botulinum toxins, particularly botulinum toxin type A, to treat conditions characterized by excessive smooth or skeletal muscle spasticity. Botulinum toxins are synthesized by Clostridium botulinum and cause temporary local paralysis of the injected muscle by inhibiting acetylcholine release at the neuromuscular junction. While botulinum toxins have Food and Drug Administration-approved labeling to treat a limited number of spasticity disorders, including cervical dystonia and blepharospasm, the toxins have more than 50 reported therapeutic uses. Among these uses, the most rigorously studied indications include achalasia, essential tremors, palmar hyperhidrosis, chronic anal fissures, headache prophylaxis, and limb spasticity. The main adverse effects of the toxins are pain and erythema at the injection site, although unintended paralysis of muscles adjacent to the site of toxin injection may also occur. CONCLUSION: Clinical studies support the use of botulinum toxins for certain conditions, although more studies are needed to establish the role of the drug relative to conventional therapies and to determine patient predictors of response. Although botulinum toxins are generally well tolerated, a patient-specific risk-benefit assessment should precede any decision to use them for unlabeled indications.

Unlabeled uses of botulinum toxins: a review, part 2.

PURPOSE: Efficacy and safety data regarding the unlabeled uses of botulinum toxins are reviewed, and the pharmacology, adverse effects, and characteristics of commercially available botulinum toxins are discussed. SUMMARY: More than 300 articles have been published on the use of botulinum toxins, particularly botulinum toxin type A, to treat conditions characterized by excessive smooth or skeletal muscle spasticity. Botulinum toxins are synthesized by Clostridium botulinum and cause temporary local paralysis of the injected muscle by inhibiting acetylcholine release at the neuromuscular junction. While botulinum toxins have Food and Drug Administration-approved labeling to treat a limited number of spasticity disorders, including cervical dystonia and blepharospasm, the toxins have more than 50 reported therapeutic uses. Among these uses, the most rigorously studied indications include achalasia, essential tremors, palmar hyperhidrosis, chronic anal fissures, headache prophylaxis, and limb spasticity. The main adverse effects of the toxins are pain and erythema at the injection site, although unintended paralysis of muscles adjacent to the site of toxin injection may also occur. CONCLUSION: Clinical studies support the use of botulinum toxins for certain conditions, although more studies are needed to establish the role of the drug relative to conventional therapies and to determine patient predictors of response. Although botulinum toxins are generally well tolerated, a patient-specific risk-benefit assessment should precede any decision to use them for unlabeled indications.

Prevalence and Therapeutic Classifications of FDA-Approved Prescription Drugs With Boxed Warnings.

PURPOSE: To characterize and determine the prevalence of drugs with boxed warnings (BXWs) based on a review of structured product labels (SPLs) available on the National Library of Medicine (NLM) DailyMed website. METHODS: A cross-sectional review was conducted of SPLs with BXWs for human prescription drugs on the NLM DailyMed website in July 2012. The presence of a BXW in the DailyMed version of the SPL was validated by cross-referencing a corresponding label on the FDA website. The SPLs were organized into drug groups, and descriptive statistics were used to determine the proportion of SPLs and drug groups associated with a validated BXW. The top therapeutic classes of drugs with BXWs were determined as well as the percentage of the top 100 BXW-associated drugs used in US hospitals and retail settings in 2012. RESULTS: Findings revealed that 35% (n = 4940/14,264) of drug labels on DailyMed and 35% (n = 650/1848) of the drug groups created were associated with a validated BXW. Central nervous system agents, antineoplastic agents, and cardiovascular drugs were the most common therapeutic classes. In 2012, 39% of the top 100 drugs were associated with a BXW.

Boxed warning inconsistencies between drug information resources and the prescribing information.

PURPOSE: Inconsistencies in boxed warnings between drug information resources and the manufacturer's prescribing information (PI) were evaluated. METHODS: This study was a cross-sectional evaluation of boxed warnings in Black-BoxRx, DrugDex, Facts and Comparisons, Epocrates, Lexicomp, and PDR.net conducted in June 2010. New molecular entities with boxed warnings and PI that conformed to current Food and Drug Administration labeling requirements were included. Each resource was reviewed for warnings that appeared verbatim with the full boxed warning in the PI. Two drug information pharmacists independently reviewed the remaining nonverbatim boxed warnings to determine concordance with the boxed warning summary in the "highlights" section of the PI. Tests of proportions were used to examine differences among resources in the proportion of warnings concordant with the PI. Interrater reliability was assessed with the kappa statistic. RESULTS: A total of 71 drugs with unique boxed warnings were included in the evaluation. Resources revealed varying degrees of discordances with the boxed warning in the PI. The resource with the lowest number of verbatim warnings contained a significantly higher percentage of warnings with discordant information when compared with all other resources (p < 0.0001 for all paired comparisons). Interrater reliability was excellent (kappa = 0.86). CONCLUSION: Boxed warning information presented in major drug information resources may be missing key elements of the official boxed warning in the current PI. The current PI may be the most reliable approach to accessing the complete, up-to-date boxed warning for a given drug.

Systematic review of medication safety assessment methods.

PURPOSE: The accuracy, efficiency, and efficacy of four commonly recommended medication safety assessment methodologies were systematically reviewed. METHODS: Medical literature databases were systematically searched for any comparative study conducted between January 2000 and October 2009 in which at least two of the four methodologies-incident report review, direct observation, chart review, and trigger tool-were compared with one another. Any study that compared two or more methodologies for quantitative accuracy (adequacy of the assessment of medication errors and adverse drug events) efficiency (effort and cost), and efficacy and that provided numerical data was included in the analysis. RESULTS: Twenty-eight studies were included in this review. Of these, 22 compared two of the methodologies, and 6 compared three methods. Direct observation identified the greatest number of reports of drug-related problems (DRPs), while incident report review identified the fewest. However, incident report review generally showed a higher specificity compared to the other methods and most effectively captured severe DRPs. In contrast, the sensitivity of incident report review was lower when compared with trigger tool. While trigger tool was the least labor-intensive of the four methodologies, incident report review appeared to be the least expensive, but only when linked with concomitant automated reporting systems and targeted follow-up. CONCLUSION: All four medication safety assessment techniques-incident report review, chart review, direct observation, and trigger tool-have different strengths and weaknesses. Overlap between different methods in identifying DRPs is minimal. While trigger tool appeared to be the most effective and labor-efficient method, incident report review best identified high-severity DRPs.

The FDA extended warning for intravenous haloperidol and torsades de pointes: how should institutions respond?

BACKGROUND: In September 2007, the Food and Drug Administration (FDA) strengthened label warnings for intravenous (IV) haloperidol regarding QT prolongation (QTP) and torsades de pointes (TdP) in response to adverse event reports. Considering the widespread use of IV haloperidol in the management of acute delirium, the specific FDA recommendation of continuous electrocardiogram (ECG) monitoring in this setting has been associated with some controversy. We reviewed the evidence for the FDA warning and provide a potential medical center response to this warning. METHODS: Cases of intravenous haloperidol-related QTP/TdP were identified by searching PubMed, EMBASE, and Scopus databases (January 1823 to April 2009) and all FDA MedWatch reports of haloperidol-associated adverse events (November 1997 to April 2008). RESULTS: A total of 70 of IV haloperidol-associated QTP and/or TdP were identified. There were 54 reports of TdP; 42 of these events were reportedly preceded by QTP. When post-event QTc data were reported, QTc was prolonged >450 msec in 96% of cases. Three patients experienced sudden cardiac arrest. Sixty-eight patients (97%) had additional risk factors for TdP/prolonged QT, most commonly receipt of concomitant proarrhythmic agents. Patients experiencing TdP received a cumulative dose of 5 mg to 645 mg, patients with QTP alone received a cumulative dose of 2 mg to 1540 mg. CONCLUSIONS: While administration of IV haloperidol can be associated with QTP/TdP, this complication most often took place in the setting of concomitant risk factors. Importantly, the available data suggest that a total cumulative dose of IV haloperidol of <2 mg can safely be administered without ongoing electrocardiographic monitoring in patients without concomitant risk factors.

Cosmetic use of botulinum toxin type A in the elderly.

Botulinum toxin type A injections are one of the most popular cosmetic procedures for diminishing the appearance of facial lines caused by habitual facial muscle contractions. Although the manufacturer's labeling recommends botulinum toxin only for the treatment of glabellar lines among adults younger than 65 years of age, there is widespread use of the toxin for other cosmetic purposes and for patients who may be older than 65. Evidence-based safety and efficacy data on botulinum toxin use in elderly patients is limited. However, given the age-related skin changes and multifactorial causes of wrinkles in the elderly, as well as the higher risk for potential side effects due to concomitant diseases and medications, a careful risk-benefit assessment should precede the decision to use botulinum toxin in the elderly patient.

Intrathecal ziconotide for refractory chronic pain.

OBJECTIVE: To describe the pharmacology, efficacy, and safety of ziconotide for treatment of severe chronic pain in patients who are candidates for intrathecal therapy. DATA SOURCES: A PubMed/MEDLINE search (1966-June 2006) was conducted using the terms ziconotide, Prialt, and SNX-111. Manufacturer-provided data, the Food and Drug Administration medical review of ziconotide, and abstracts presented at American Pain Society meetings (2001-2006) were also reviewed. STUDY SELECTION AND DATA EXTRACTION: Human studies evaluating the efficacy and safety of ziconotide for the treatment of chronic pain were considered. Animal data were excluded. DATA SYNTHESIS: Ziconotide is the first and only neuronal-type (N-type) calcium-channel blocker. Ziconotide must be administered intrathecally via continuous infusion. A programmable implanted variable-rate microinfusion device, or an external microinfusion device and catheter must be utilized. In double-blind, placebo-controlled studies, ziconotide significantly improved patient perception of pain from baseline to the end of the study periods, which ranged from 11 to 21 days. Patients enrolled in clinical trials were intolerant of or refractory to other treatment modalities. There have been no studies that directly compared ziconotide with other intrathecal or systemic analgesics. Key ziconotide-related adverse events are neuropsychiatric, including depression, cognitive impairment, and hallucinations; depressed levels of consciousness; and elevation of creatine kinase levels. Ziconotide is also associated with a risk of meningitis due to possible contamination of the microinfusion device. CONCLUSIONS: Ziconotide is a therapeutic option for treatment of severe chronic pain in patients who have exhausted all other agents, including intrathecal morphine, and for whom the potential benefit outweighs the risks of serious neuropsychiatric adverse effects and of having an implanted device. Further studies are needed to determine the comparative efficacy of ziconotide and other pain therapies.