Analysis of iron status after initiation of elexacaftor/tezacaftor/ivacaftor in people with cystic fibrosis.

BACKGROUND: Iron deficiency is highly prevalent in people with cystic fibrosis (PwCF). While elexacaftor/tezacaftor/ivacaftor (ETI) has shown remarkable improvements in respiratory symptoms in PwCF, the effect of ETI on iron status remains unknown. This study aims to identify the effect of ETI on iron status in PwCF. METHODS: A single-center retrospective cohort study of 127 adult PwCF was conducted to assess the impact of ETI on iron, ferritin, transferrin levels, and percent saturation of transferrin (PSAT). Data were collected from the electronic medical record from January 2017 to September 2022, encompassing 2 years before and after ETI initiation. The primary outcome was serum iron parameters: iron, ferritin, transferrin, and PSAT levels following ETI treatment. Secondary outcomes analyzed iron supplementation. Univariate and multivariate mixed-effects models were used for the analysis of ETI. RESULTS: After adjusting for covariates, following ETI initiation, the mean iron level increased by 20.24 µg/dL (p < .001), ferritin levels were 31.4% (p < .001) higher, PSAT showed a 5.09 percentage point increase (p < .001), and transferrin levels increased by 2.71 mg/dL (p = .439). Patients with and without iron supplementation experienced a significant increase in iron after ETI (p < .001). CONCLUSIONS: ETI is associated with a significant increase in iron, ferritin, and PSAT levels. Patients with and without iron supplementation demonstrated a significant increase in iron. This study shows the benefits of ETI on iron status in PwCF. However, further translational studies are required to understand the impact of ETI on iron absorption and metabolism in PwCF.

Changes in nutrition and growth status in young children in the first 12 weeks of ivacaftor therapy.

BACKGROUND: Highly effective CFTR modulators improve nutritional status and are of particular importance among younger children experiencing rapid growth. This study was designed to examine CFTR modulator associated changes in nutritional and other extrapulmonary outcomes in children 4-24 months of age with ivacaftor treatment over 12 weeks. METHODS: Children 4-24 months were recruited from US and Canadian CF Centers. Eligible children were ivacaftor naïve and approved to start therapy. Anthropometrics, diet, sleeping energy expenditure (SEE), nutrition biomarkers, pancreatic status, serum and fecal calprotectin, serum bile acids, plasma fatty acids were measured. Changes from baseline at 6 and 12 weeks were examined using mixed effects linear regression modeling. RESULTS: Fifteen participants enrolled (40% male). Weight-for-age z-scores increased at 6 (p = 0.03) and 12 weeks ivacaftor therapy (p<0.001) compared to baseline. Plasma docosatetraenoic acid (DTA), total saturated fatty acids increased at 6 weeks (p = 0.02) and 12 weeks (p = 0.009). At 12 weeks, serum CO2 concentration decreased (p = 0.002), serum urea nitrogen increased (p = 0.01) and fecal elastase increased (p = 0.02) compared to baseline. Bile acids, deoxycholic acid increased (p = 0.03) and ursodeoxycholic acid decreased (p = 0.02) after 12 weeks. Plasma total fatty acids, palmitic acid, mead, and docosatetraenoic acid (DTA) increased after 12 weeks (p = 0.02, p = 0.002 and p = 0.04, respectively). Plasma total saturated fatty acids increased at 6 weeks (p = 0.02) and 12 weeks (p = 0.009). Dietary intake (p = 0.04) and percent kcal from protein (p = 0.04) increased after 12 weeks compared to baseline. CONCLUSIONS: Overall, younger children experienced favorable changes in nutritional and growth status in the first 12 weeks of ivacaftor therapy.

Impact of highly effective CFTR modulator therapy on digital clubbing in patients with cystic fibrosis.

BACKGROUND: The association of certain disease processes with digital clubbing is well documented. Digital clubbing is often reversible after successful treatment of the underlying pathology, for example, after lung transplantation in patients with cystic fibrosis (CF). We examined the effect of highly effective Cystic Fibrosis Transmembrane Regulator (CFTR) modulators, defined for the purposes of this study as ivacaftor or the combination of ivacaftor, tezacaftor, and elexacaftor (ETI), on digital clubbing. MATERIALS AND METHODS: Clubbing index was measured on plaster of Paris casts of right index fingers obtained from 15 patients with cystic fibrosis, before and after initiation of CFTR modulator therapy. Similar measurements were made on casts for 9 cystic fibrosis patients who underwent lung transplantation. Measurements were made on the most recent casts available before treatment and the first cast available at least 3 months after initiation of treatment. The Wilcoxon signed-rank text was used to detect any significant difference in the pre- and post-treatment casts for each individual. RESULTS: A significant decrease in the clubbing index was found after both lung transplantation and treatment with highly effective CFTR modulator therapy. CONCLUSIONS: These results add to the body of evidence demonstrating the efficacy of highly effective CFTR modulator therapy, the first agents that act directly at the dysfunctional chloride channel responsible for CF. By demonstrating that CFTR modulator therapy is capable of reversing digital clubbing, this study suggests a beneficial effect on lung pathology aside from air flow and gas transfer.

Impact of elexacaftor/tezacaftor/ivacaftor on vitamin D absorption in cystic fibrosis patients.

BACKGROUND: Cystic fibrosis (CF) is a multisystem disorder that results in the buildup of mucus in various organs. Ninety percent of CF patients are classified as pancreatic insufficient, leading to malabsorption of nutrients and fat-soluble vitamins without the assistance of exogenous pancreatic enzymes. This study was designed to determine if serum 25-hydroxyvitamin D concentrations were impacted by initiation of elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA). METHODS: Serum 25-hydroxyvitamin D concentrations were measured before and 1 year post-ELX/TEZ/IVA initiation. A Wilcoxon signed-rank test was used to compare values. RESULTS: Seventy-six patients were included in the final analysis. The average age of our population was 25.8 years (SD = 13.2 years) with a majority being male, homozygous F508del, pancreatic insufficient, and not modulator-naive. The median increase of serum vitamin D concentration after initiating ELX/TEZ/IVA was 5 ng/ml (interquartile range = -4, 13; p = .0035). CONCLUSIONS: We suggest that ELX/TEZ/IVA may improve fat-soluble vitamin absorption, specifically serum 25-hydroxyvitamin D. These results may lead to adjustments in vitamin supplementation in patients receiving cystic fibrosis transmembrane conductance regulator modulator therapy.

Emerging preclinical modulators developed for F508del-CFTR have the potential to be effective for ORKAMBI resistant processing mutants.

BACKGROUND: F508del is prototypical of Class 2 CFTR mutations associated with protein misprocessing and reduced function. Corrector compounds like lumacaftor partially rescue the processing defect of F508del-CFTR whereas potentiators like ivacaftor, enhance its channel activity once trafficked to the cell surface. We asked if emerging modulators developed for F508del-CFTR can rescue Class 2 mutations previously shown to be poorly responsive to lumacaftor and ivacaftor. METHODS: Rescue of mutant CFTRs by the correctors: AC1, AC2-1 or AC2-2 and the potentiator, AP2, was studied in HEK-293 cells and in primary human nasal epithelial (HNE) cultures, using a membrane potential assay and Ussing chamber, respectively. RESULTS: In HEK-293 cells, we found that a particular combination of corrector molecules (AC1 plus AC2-1) and a potentiator (AP2) was effective in rescuing both the misprocessing and reduced function of M1101K and G85E respectively. These findings were recapitulated in patient-derived nasal cultures, although another corrector combination, AC1 plus AC2-2 also improved misprocessing in these primary tissues. Interestingly, while this corrector combination only led to a modest increase in the abundance of mature N1303K-CFTR it did enable its functional expression in the presence of the potentiator, AP2, in part, because the nominal corrector, AC2-2 also exhibits potentiator activity. CONCLUSIONS: Strategic combinations of novel modulators can potentially rescue Class 2 mutants thought to be relatively unresponsive to lumacaftor and ivacaftor.

Ivacaftor Reverses Airway Mucus Abnormalities in a Rat Model Harboring a Humanized G551D-CFTR.

Rationale: Animal models have been highly informative for understanding the characteristics, onset, and progression of cystic fibrosis (CF) lung disease. In particular, the CFTR-/- rat has revealed insights into the airway mucus defect characteristic of CF but does not replicate a human-relevant CFTR (cystic fibrosis transmembrane conductance regulator) variant.Objectives: We hypothesized that a rat expressing a humanized version of CFTR and harboring the ivacaftor-sensitive variant G551D could be used to test the impact of CFTR modulators on pathophysiologic development and correction.Methods: In this study, we describe a humanized-CFTR rat expressing the G551D variant obtained by zinc finger nuclease editing of a human complementary DNA superexon, spanning exon 2-27, with a 5' insertion site into the rat gene just beyond intron 1. This targeted insertion takes advantage of the endogenous rat promoter, resulting in appropriate expression compared with wild-type animals.Measurements and Main Results: The bioelectric phenotype of the epithelia recapitulates the expected absence of CFTR activity, which was restored with ivacaftor. Large airway defects, including depleted airway surface liquid and periciliary layers, delayed mucus transport rates, and increased mucus viscosity, were normalized after the administration of ivacaftor.Conclusions: This model is useful to understand the mechanisms of disease and the extent of pathology reversal with CFTR modulators.

Italian and North American dietary intake after ivacaftor treatment for Cystic Fibrosis Gating Mutations.

BACKGROUND: In patients with cystic fibrosis (CF), ivacaftor treatment results in significant weight gain and the impact on diet has not been explored. METHODS: A study in 22 subjects (6.1-61.6 years) compared diet, energy balance, weight gain, and body composition, before and after three months of treatment in Italians and North Americans with CFTR gating mutations. RESULTS: With no differences between groups in energy or macronutrient intake at baseline, fat intake increased in all subjects, and both fat and energy intake increased in Italians. Height, weight, BMI, lean and fat mass, and % body fat increased and resting energy expenditure decreased after treatment. Weight gain was associated with energy and fat intake. CONCLUSIONS: Fat intake increased with treatment, possibly due to the recommendation to take ivacaftor with high fat meals. Increased energy and fat intake correlated with weight gain. Regional dietary patterns differed.

Cost-Effectiveness and Budget Impact of Lumacaftor/Ivacaftor in the Treatment of Cystic Fibrosis.

BACKGROUND: Cystic fibrosis (CF) is a chronic, progressive, genetic disease affecting more than 30,000 people in the United States and 70,000 people globally. The goals of treatment are to slow disease progression, reduce pulmonary exacerbations, relieve chronic symptoms, and improve the patient's quality of life. Lumacaftor/ivacaftor is a new therapy for CF that has demonstrated good clinical outcomes, including improved absolute percentage predicted forced expiratory volume in 1 second (FEV1%). However, given the high cost of therapy, there is a need to evaluate the overall value of lumacaftor/ivacaftor in CF management. OBJECTIVES: To (a) conduct a cost-effectiveness analysis (CEA) of lumacaftor/ivacaftor to understand the overall effectiveness of the drug compared with its costs and (b) conduct a budget impact analysis (BIA) to understand the potential financial effect of introducing a new drug in a health plan. METHODS: Two static decision models were developed using Microsoft Excel to evaluate the cost-effectiveness and budget impact of lumacaftor/ivacaftor over a 1-year time frame from a payer perspective. Model inputs included drug costs (wholesale acquisition costs), drug monitoring schedules (package inserts), drug monitoring costs (Centers for Medicare & Medicaid physician fee schedule and published literature), FEV1% predicted and pulmonary exacerbation values (clinical trials), and cost to treat pulmonary exacerbations (published literature). The outcomes in the CEA included total cost of therapy; average cost-effectiveness ratio (ACER), defined as cost per FEV1% predicted; and incremental cost-effectiveness ratio (ICER), defined as the difference in the ratio of cost per FEV1% predicted of lumacaftor/ivacaftor and placebo. Outcomes in the BIA included total budget impact; cost per member per month (PMPM), defined as total budget impact per hypothetical plan population; and cost per treated member per month (PTMPM), defined as total budget impact per target CF population. All costs were adjusted to 2016 dollars, and one-way sensitivity analyses were conducted to test the model robustness given uncertainty in model inputs and study assumptions. RESULTS: The annual cost of therapy per patient for lumacaftor/ivacaftor was $379,780. The ACER for lumacaftor/ivacaftor was $151,912, while the ICER for lumacaftor/ivacaftor compared with placebo was $95,016 per FEV1% predicted. The annual total budget impact due to the inclusion of lumacaftor/ivacaftor on the health plan formulary was $266,046. The PMPM cost was $0.02 and the PTMPM cost was $6.21. CONCLUSIONS: In patients with CF, lumacaftor/ivacaftor has demonstrated better clinical effectiveness compared with placebo alongside an increased drug acquisition cost. However, the therapy may be a viable alternative to existing standard therapy over a short time horizon. Health care payers, both private and public, need to evaluate the cost-effectiveness and the financial effect when considering expansion of new drug coverage in CF management. DISCLOSURES: No outside funding supported this study. Covvey and Kamal have received research funding from Novartis Pharmaceuticals. Covvey, Giannetti, and Kamal have received research funding from the College of Psychiatric and Neurologic Pharmacists. Kamal serves as a consultant to the Lynx Group (Cranbury, NJ) and Manticore Consulting Group (Scottsdale, AZ). Mukherjee has nothing to disclose. A related poster abstract was presented at the AMCP Managed Care & Specialty Pharmacy Annual Meeting; March 27-30, 2017; Denver, CO.

Impact of a cystic fibrosis transmembrane conductance regulator (CFTR) modulator on high-dose ibuprofen therapy in pediatric cystic fibrosis patients.

BACKGROUND: This study was undertaken to determine if a clinically relevant drug-drug interaction occurred between ibuprofen and lumacaftor/ivacaftor. METHODS: Peak ibuprofen plasma concentrations were measured prior to and after lumacaftor/ivacaftor initiation. A Wilcoxon signed rank sum test was used to compare the values. RESULTS: Nine patients were included in the final analysis. Peak ibuprofen plasma concentrations decreased an average of 36.4 mcg/mL after initiation of lumacaftor/ivacaftor with a relative reduction of 41.7%. The average peak plasma concentration was 84.2 mcg/mL (SD = 10.9) prior to lumacaftor/ivacaftor initiation and 47.9 mcg/mL (SD = 16.4) following initiation (P = 0.0039). Peak concentrations occurred at an average of 100 min (SD = 30) and 107 min (SD = 40) prior to and following lumacaftor/ivacaftor initiation, respectively. CONCLUSIONS: We suggest a clinically relevant drug-drug interaction exists between ibuprofen and lumacaftor/ivacaftor. Lumacaftor may cause subtherapeutic ibuprofen plasma concentrations due to the induction of CYP enzymes and increased metabolism of ibuprofen. Based on this analysis, we have modified our use of ibuprofen in several patients after evaluation of this drug-drug interaction.

Adherence to therapies in cystic fibrosis: a targeted literature review.

INTRODUCTION: Cystic fibrosis (CF) is a life-shortening condition with no cure. Available therapies relieving the symptoms of CF are complex and time-consuming. A comprehensive review assessing adherence to different CF therapies, association of adherence with outcomes, and factors influencing adherence could inform optimal patient management strategies. Areas covered: A targeted literature review of studies published from 2010-2016 assessed adherence to CF therapies. Nineteen studies qualified for inclusion. Adherence to CF therapies was sub-optimal, and varied by treatment, mode of treatment administration, age, season, time and method of adherence measurement. Adherence to ivacaftor and inhaled antibiotics were reported higher than dornase alfa or hypertonic saline, oral pancreatic enzyme and vitamin supplements, and airway clearance therapy. Several patient, healthcare provider and treatment related factors influenced adherence. Sub-optimal adherence was shown to impact clinical and economic burden of the disease. Expert commentary: Higher adherence to CF therapies can lower disease burden, and improve patient outcomes. Healthcare providers and policy makers should devise patient-centered and caregiver-enabled interventions to improve adherence. Research on long-term adherence and outcomes associated with promising oral treatments such as CFTR modulators is needed. Identifying ways to overcome key barriers to adherence can positively affect outcomes associated with CF.

Advancing clinical development pathways for new CFTR modulators in cystic fibrosis.

Cystic fibrosis (CF) is a life-shortening genetic disease affecting approximately 70,000 individuals worldwide. Until recently, drug development efforts have emphasised therapies treating downstream signs and symptoms resulting from the underlying CF biological defect: reduced function of the CF transmembrane conductance regulator (CFTR) protein. The current CF drug development landscape has expanded to include therapies that enhance CFTR function by either restoring wild-type CFTR protein expression or increasing (modulating) the function of mutant CFTR proteins in cells. To date, two systemic small-molecule CFTR modulators have been evaluated in pivotal clinical trials in individuals with CF and specific mutant CFTR genotypes that have led to regulatory review and/or approval. Advances in the discovery of CFTR modulators as a promising new class of therapies have been impressive, yet work remains to develop highly effective, disease-modifying modulators for individuals of all CF genotypes. The objectives of this review are to outline the challenges and opportunities in drug development created by systemic genotype-specific CFTR modulators, highlight the advantages of sweat chloride as an established biomarker of CFTR activity to streamline early-phase development and summarise options for later phase clinical trial designs that respond to the adoption of approved genotype-specific modulators into standard of care. An optimal development framework will be needed to move the most promising therapies efficiently through the drug development pipeline and ultimately deliver efficacious and safe therapies to all individuals with CF.

Novel resveratrol analogues attenuate renal ischemic injury in rats.

BACKGROUND: Renal ischemia-reperfusion (I/R) is a severe clinical complication with no specific treatment. Resveratrol has been shown as a promising experimental agent in renal I/R due to its effect on cellular energy metabolism, oxidative stress, and inflammation. Recently, we identified two biologically active resveratrol analogues (RSVAs), RSVA405 and RSVA314. We hypothesized that both RSAVs would attenuate I/R-induced renal injury. METHODS: Adult male rats were subjected to renal I/R through bilateral renal pedicle clamping for 60 min, followed by reperfusion. RSVA405 (3 mg/kg Body Weight), RSVA314 (3 mg/kg Body Weight), or vehicle (10% dimethyl sulfoxide and 33% Solutol in phosphate buffered saline) were administered by intraperitoneal injection 1 h before ischemia. Blood and renal tissues were collected 24 h after I/R for evaluation. RESULTS: Administration of RSVA405 and RSVA314 significantly reduced the serum levels of renal dysfunction and injury markers, including creatinine, blood urea nitrogen, aspartate aminotransferase, and lactate dehydrogenase, compared with vehicle. The protective effect of RSVA405 and RSVA314 was also reflected on histologic evaluation. Both RSVAs reduced the number of apoptotic cells by more than 60% as determined by transferase dUTP nick end labeling assay, compared with vehicle. The renal adenosine triphosphate levels of the vehicle group was decreased to 52.4% of control, whereas those of the RSVA405 and RSVA314 groups were restored to 72.3% and 79.6% of control, respectively. Both RSVAs significantly reduced the protein expression of inducible nitric oxide synthase and nitrotyrosine and the messenger RNA levels of tumor necrosis factor-α, interleukin-6, and interleukin-1ß. CONCLUSIONS: RSVA405 and RSVA314 attenuate I/R-induced renal injury through the modulation of energy metabolism, oxidative stress, and inflammation.

Inhibiting glycogen synthase kinase-3 mitigates the hematopoietic acute radiation syndrome in mice.

Exposure to a nuclear accident or radiological attack can cause death from acute radiation syndrome (ARS), which results from radiation injury to vital organs such as the hematopoietic system. However, the U.S. Food and Drug Administration (FDA) has not approved any medical countermeasures for this specific purpose. With growing concern over nuclear terrorism, there is an urgent need to develop small molecule deliverables that mitigate mortality from ARS. One emerging modulator of hematopoietic stem/progenitor cell (HSPC) activity is glycogen synthase kinase-3 (GSK-3). The inhibition of GSK-3 has been shown to augment hematopoietic repopulation in mouse models of bone marrow transplantation. In this study, we performed an in vitro screen using irradiated bone marrow mononuclear cells (BM-MNCs) to test the effects of four GSK-3 inhibitors: CHIR99021; 6-Bromoindirubin-3'-oxime (BIO); SB415286; and SB216763. This screen showed that SB216763 significantly increased the frequency of c-Kit(+) Lin(-) Sca1(+) (KLS) cells and hematopoietic colony-forming cells in irradiated BM-MNCs. Importantly, administration of a single dose of SB216763 to C57BL/6J mice by subcutaneous injection 24 h after total-body irradiation significantly improved hematopoietic recovery and mitigated hematopoietic ARS. Collectively, our results demonstrate that the GSK-3 inhibitor SB216763 is an effective medical countermeasure against acute radiation injury of the hematopoietic system.

Therapies for musculoskeletal disease: can we treat two birds with one stone?

Musculoskeletal diseases are highly prevalent with staggering annual health care costs across the globe. The combined wasting of muscle (sarcopenia) and bone (osteoporosis)-both in normal aging and pathologic states-can lead to vastly compounded risk for fracture in patients. Until now, our therapeutic approach to the prevention of such fractures has focused solely on bone, but our increasing understanding of the interconnected biology of muscle and bone has begun to shift our treatment paradigm for musculoskeletal disease. Targeting pathways that centrally regulate both bone and muscle (eg, GH/IGF-1, sex steroids, etc.) and newly emerging pathways that might facilitate communication between these 2 tissues (eg, activin/myostatin) might allow a greater therapeutic benefit and/or previously unanticipated means by which to treat these frail patients and prevent fracture. In this review, we will discuss a number of therapies currently under development that aim to treat musculoskeletal disease in precisely such a holistic fashion.

Calcium entry inhibition during resuscitation from shock attenuates inflammatory lung injury.

Trauma and hemorrhagic shock (T/HS) induce a systemic inflammatory response syndrome (SIRS). Neutrophils (polymorphonuclear leukocytes [PMN]) and other cells involved in acute lung injury (ALI) are activated by Ca2+ entry. Thus, inhibiting Ca2+ entry might attenuate post-traumatic lung injury. Inhibiting voltage-operated (L-type) Ca2+ channels during shock could cause cardiovascular collapse, but PMN are "nonexcitable" cells, lack L-type channels, and mobilize Ca2+ via nonspecific channels. We previously showed that PMN Ca2+ entry requires sphingosine 1-phosphate synthesis by sphingosine kinase and that both sphingosine kinase inhibition and blockade of nonspecific channels attenuate ALI when begun before shock. Pretreatment for clinical injuries, however, is impractical. Therefore, we now studied whether Ca2+ entry inhibition that begun during resuscitation from T/HS could attenuate SIRS and ALI without causing hemodynamic compromise. Male Sprague-Dawley rats underwent laparotomy and fixed-pressure shock (mean arterial pressure, 35 +/- 5 mmHg; 90 min). Sphingosine kinase inhibition or nonspecific Ca2+ channel inhibition was begun after resuscitation with 10% of shed blood. We then studied in vivo PMN activation and associated lung injury in the presence or absence of Ca2+ entry inhibition. Neither treatment worsened shock. Each treatment decreased CD11b expression, respiratory burst, PMN p38 MAP-kinase phosphorylation, PMN sequestration, and lung capillary leak in vivo. The similar results seen with two different forms of inhibition strengthen the conclusion that the biological effects seen were specific for calcium entry inhibition. Ca2+ entry inhibition is a candidate therapy for management of lung injury after shock.

Toxicity evaluation of two treatment regimens for cyanide poisoning.

Toxicological evaluation of two recently reported treatment protocols for cyanide--SN (sodium nitrite) + DMAP (4-dimethylaminophenol) and SN + HA (hydroxylamine)--was carried out in male rats. Both treatments produced transient hyperammonaemia and decreased mean arterial pressure. Heart rate decreased and respiratory rate increased, but these changes reached the level of significance only after SN + HA. Histopathological lesions in lung, liver (SN+HA) and kidney (SN+DMAP) were predominantly in the vicinity of blood vessels. The results indicate toxic effects in both treatment groups at a dose known to induce methaemoglobin concentration to the level of antidotal efficiency in cyanide intoxication.

[Cyanide poisoning]. / Cyanid-Intoxikation.

Acute cyanide poisoning is a rare but usually fatal intoxication. Rapid diagnosis and immediate initiation of therapy are important, since a number of effective and potentially life-saving antidotes are available. Pathophysiology, signs, symptoms, course and therapy are discussed, and three personal observations are presented.

Circulation, respiration, and blood homeostasis in cyanide-poisoned dogs after treatment with 4-dimethylaminophenol or cobalt compounds.

The effects of intravenously injected 4-dimethylaminophenol-HCl (DMAP), Co2EDTA, and Co(histidine)2 on the survival rate and several physiological parameters were studied on dogs after acute intravenous poisoning with the double lethal dose of potassium cyanide. All dogs survived when the antidotes were administered 1 min after poisoning. When the therapy began 4 min after poisoning more dogs were rescued in the DMAP group than in the cobalt groups. DMAP, Co2EDTA, and Co(histidine)2 restored circulation and respiration of the surviving animals in a similar manner. The increase in the plasma concentrations of glucose and lactate was much higher in the Co2EDTA group than in the DMAP group. The injection of Co2EDTA produced a sharp rise in the lactate-to-pyruvate ratio. The lactate-to-pyruvate ratio stayed unchanged for some 15 min after injection of DMAP before also rising. The total dose of KCN (4 mg/kg) was bound to the ferrihemoglobin formed by DMAP. The arterial pO2 increase, caused by liberation of oxygen from oxyhemoglobin during the formation of ferrihemoglobin, was less when the cyanide could act on the tissues for a longer period of time before the therapy with DMAP began. DMAP is more appropriate for the therapy of cyanide poisoning than Co2EDTA, since the latter adds its inhibitory effects on the metabolism to those of cyanide.