Myofilament Ca²⁺ sensitivity (EC₅₀ for positive inotropic effect: >16 μM in dog, 9.0 μM in rabbit, 9.2 μM in guinea pig) [1]
Phosphodiesterase III (PDE III): IC₅₀ = 64.9 μM (95% CI: 43.3–97.0 μM) [1]
Delayed rectifier K⁺ channels (no IC₅₀ provided; prolongs action potential duration) [1]
Na⁺,K⁺-ATPase: no inhibition up to 100 μM [1]
β-adrenoceptors: no agonist activity (positive inotropic effect not blocked by β-blockers) [1]

SCH00013 elicits a positive inotropic effect mainly through an increase in myofilament Ca2+ sensitivity without increasing the heart rate. Lack of a positive chronotropic effect may be an important benefit because tachycardia causes an excessive energy consumption and drives the negative force-frequency relationship in severe CHF patients. In addition, SCH00013 possesses class III antiarrhythmic action. While the major potential disadvantage of Ca2+ sensitizers is postulated to be aggravation of the diastolic dysfunction in a failing heart, the effect of SCH00013 on diastolic function was much less than that induced by EMD 57033 in rabbit ventricular myocytes.

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SCH00013 (CAS#: 217963-18-3) in vitro: In isolated dog, rabbit, and guinea pig ventricular muscles, SCH00013 produced a concentration-dependent positive inotropic effect, with maximum effects at 100 μM of 43.3%, 29.4%, and 57.4% of isoproterenol maximal response, respectively. EC₅₀ values: >16 μM (dog), 9.0 μM (rabbit), 9.2 μM (guinea pig). The effect was not blocked by β-adrenoceptor antagonists (buparolol, propranolol). Carbachol (3-10 μM) partially inhibited but did not abolish the positive inotropic effect, suggesting a major Ca²⁺ sensitizing component. [1]
In rabbit ventricular cardiomyocytes loaded with indo-1, SCH00013 (100 μM) increased cell shortening to 152.1% of control without a significant change in systolic indo-1 fluorescence ratio (Ca²⁺ transient), indicating Ca²⁺ sensitization. EMD 57033 (3 μM) increased cell shortening to 233.7% with no change in Ca²⁺ transient. SCH00013 did not affect the time course of Ca²⁺ transients or cell shortening, and had minimal effect on diastolic cell length. [1]
SCH00013 (up to 100 μM) did not inhibit Na⁺,K⁺-ATPase from guinea pig heart. [1]
SCH00013 inhibited PDE III from guinea pig heart with IC₅₀ = 64.9 μM, but had no effect on PDE I, II, or IV (IC₅₀ >300 μM). The relationship between PDE III inhibition and contractile force increase was shifted leftward compared to milrinone and vesnarinone, indicating that PDE III inhibition plays a minor role in its inotropic effect. [1]
SCH00013 (10-100 μM) concentration-dependently prolonged action potential duration and effective refractory period in guinea pig papillary muscles, with little change in resting membrane potential, amplitude, or upstroke velocity. [1]
In guinea pig thoracic aorta helical strips precontracted with norepinephrine (10 μM), SCH00013 produced concentration-dependent relaxation (vasodilation), with potency similar to vesnarinone but less than milrinone. [1]
In spontaneously beating rabbit and guinea pig right atria, SCH00013 (up to 10 μM) did not increase but slightly decreased the spontaneous rate, showing no positive chronotropic effect. [1]

SCH00013 had little effect on the rate of cardiac relaxation, an indication that the aggravation of diastolic dysfunction may not be a serious complication compared with other Ca2+ sensitizers such as EMD 57033. SCH00013 has a high oral bioavailability in dogs and a high safety margin in rats
SCH00013 (CAS#: 217963-18-3) in vivo: In anesthetized dogs, intravenous SCH00013 (0.3–10 mg/kg) dose-dependently increased left ventricular dP/dtmax (maximum rate of rise of left ventricular pressure), with peak effect within 1 min and duration >30 min. Heart rate was not significantly changed. At ≥3 mg/kg, moderate biphasic decreases in systolic and diastolic blood pressure were observed. [1]
In conscious dogs, oral SCH00013 (1–10 mg/kg) dose-dependently increased LVP dP/dtmax with threshold at 3 mg/kg; at 10 mg/kg, effect lasted ~4 h. Heart rate did not significantly change. [1]
In adrenaline-induced arrhythmia model, intravenous SCH00013 at 3 mg/kg induced ventricular fibrillation (VF) in 2 out of 3 dogs; at 1 mg/kg, no VF occurred. Vesnarinone at 1 mg/kg induced VF in all dogs. [1]
In digitalis-induced arrhythmia model, SCH00013 (3 mg/kg i.v.) showed a tendency to suppress arrhythmia (lowered arrhythmic ratio). Vesnarinone (3 mg/kg) did not improve it. [1]
In two-stage coronary ligation-induced arrhythmia, SCH00013 (1 and 3 mg/kg i.v.) tended to improve arrhythmia at 48 h (1 mg/kg) and 24 h (3 mg/kg), but differences were not statistically significant. Vesnarinone aggravated arrhythmia. [1]
In hereditary cardiomyopathy hamsters (BIO 14.6 strain), SCH00013 administered in drinking water (1 or 10 mg/kg/day) prolonged survival. Median survival times: control 169 days; 1 mg/kg 173 days; 10 mg/kg 222 days. The 10 mg/kg group showed a significant increase in survival rate compared to control (log-rank test, p<0.01). [1]

PDE III enzyme assay (from [1]): PDE I, II, III, and IV were isolated from guinea pig heart homogenates. Enzyme activity was measured using [³H]cAMP or [³H]cGMP as substrates. The IC₅₀ values were determined by incubating the enzyme with various concentrations of SCH00013, milrinone, or vesnarinone. The final concentration of DMSO in the assay was 1.0%, which inhibited PDE activity by about 7%. [1]
Na⁺,K⁺-ATPase assay: Enzyme was prepared from guinea pig heart. Activity was measured by the release of inorganic phosphate. SCH00013 was tested up to 100 μM; ouabain was used as a positive control. [1]

Rabbit ventricular cardiomyocyte isolation and indo-1 loading (from [1]): Single ventricular myocytes were isolated from rabbit hearts. Cells were loaded with the Ca²⁺ indicator indo-1 AM (5 μM) for 20 min at 37°C. Simultaneous measurements of indo-1 fluorescence ratio (excitation 365 nm, emission at 405 and 495 nm) and cell shortening (via video edge detection) were performed during electrical stimulation (0.5–1 Hz). SCH00013 (1–100 μM) was added cumulatively. Data were analyzed as percentage change from control. [1]
Isolated cardiac muscle preparations: Right ventricular papillary muscles or trabeculae from dog, rabbit, and guinea pig were mounted in organ baths containing Tyrode or Krebs-Henseleit solution (37°C, gassed with 95% O₂/5% CO₂), stimulated at 0.5–1 Hz. Isometric force was recorded. Concentration-response curves for SCH00013 (0.1–100 μM) were constructed; in some experiments, carbachol (3–10 μM) or β-blockers were added. [1]
Spontaneously beating right atria: Isolated rabbit or guinea pig right atria were mounted and allowed to beat spontaneously; rate was recorded. [1]
Vascular smooth muscle: Helical strips of guinea pig thoracic aorta were precontracted with norepinephrine (10 μM). Cumulative concentrations of SCH00013, milrinone, or vesnarinone were added, and relaxation was expressed as percentage of papaverine (100 μM)-induced maximal relaxation. [1]

Animal protocols (from [1]): Anesthetized dogs: Beagle dogs (both sexes) were anesthetized with pentobarbital sodium (30 mg/kg i.v.). Left ventricular pressure, dP/dt, systemic blood pressure, and ECG were recorded. SCH00013 (0.3–10 mg/kg) was administered intravenously (bolus) and effects monitored for 30 min. n=5 per dose. [1]
Conscious dogs: Beagle dogs with chronically implanted pressure transducers in the left ventricle received oral SCH00013 (1, 3, 10 mg/kg) via gavage. LVP dP/dt, heart rate, and blood pressure were recorded for up to 6 h. n=3-5 per dose. [1]
Adrenaline-induced arrhythmia: Anesthetized dogs received continuous intravenous infusion of epinephrine (0.5 μg/kg/min). After stable arrhythmia, SCH00013 or vesnarinone was given i.v. (0.3–3 mg/kg). Incidence of ventricular fibrillation was recorded. [1]
Digitalis-induced arrhythmia: Dogs were given digitoxin (0.07–0.09 mg/kg i.v.) to induce ventricular arrhythmia. Then SCH00013 or vesnarinone (3 mg/kg i.v.) was administered, and the arrhythmic ratio (number of ventricular ectopic beats/total heart beats ×100) was measured over time. [1]
Two-stage coronary ligation: Dogs underwent two-stage ligation of the left anterior descending coronary artery. At 24 h and 48 h after ligation, SCH00013 (1 or 3 mg/kg i.v.) was given, and heart rate, blood pressure, and arrhythmias (total heart rate, conducted beats, atrial rate) were recorded for 60 min. [1]
Cardiomyopathy hamster: Male BIO 14.6 strain hamsters (aged 223 days) were given SCH00013 in drinking water at doses of 1 or 10 mg/kg/day (based on water consumption). Control received tap water. Survival was monitored daily; median survival time was calculated. n=23 per group. [1]

Dog pharmacokinetics (from [1]): SCH00013 was administered intravenously (3 mg/kg) or orally (3 mg/kg) to beagle dogs (n=3 for IV, n=4 for oral). Plasma concentrations were determined by high-performance liquid chromatography (HPLC). Pharmacokinetic parameters (mean ± SEM): IV: AUC₀-₂₄h = 15.3 ± 2.0 μg·h/mL, t₁/₂ = 13.2 ± 4.4 h. Oral: AUC₀-₂₄h = 16.5 ± 2.1 μg·h/mL, t₁/₂ = 12.7 ± 2.1 h, Tmax = 1.69 ± 0.31 h, Cmax = 1.16 ± 0.17 μg/mL. Bioavailability was high (oral AUC similar to IV). [1]

Acute toxicity in rats: Oral administration of SCH00013: minimum lethal dose estimated between 178 and 267 mg/kg (1/5 died at 267 mg/kg, 2/5 at 400 mg/kg). Intravenous administration: minimum lethal dose between 86 and 95 mg/kg (1/5 died at 95 mg/kg, 5/5 at 112 mg/kg). [1]
Repeated oral toxicity (28 days) in rats: Doses of 20, 60, and 180 mg/kg/day (n=6 each). No deaths occurred at any dose. At 60 and 180 mg/kg, suppression of body weight gain and food intake was observed. At 180 mg/kg, elevations of GOT (AST), GPT (ALT), and BUN, and slight spermatid injury in testis were seen. All changes recovered after 14-day withdrawal. No adverse effect level was estimated at 20 mg/kg. [1]
Mutagenicity: SCH00013 was not mutagenic in the Ames test (bacterial reverse mutation) using S. typhimurium TA1535, TA100, TA1537, TA1538, TA98 and E. coli WP2uvrA, with or without S9 mix, at concentrations up to 5000 μg/plate. Chromosomal aberration test in Chinese hamster lung V79 cells (25–100 mg/mL) was negative. Mouse micronucleus test (oral doses 30, 100, 300 μg/kg) was negative. [1]

:Cardiovasc Drug Rev. 2001 Winter;19(4):345-66.;J Pharmacol Sci. 2005 Jan;97(1):53-60.

SCH00013 is a racemic mixture with an asymmetric carbon; both enantiomers ((+)- and (-)-SCH00013) showed essentially equivalent pharmacological activities (Ca²⁺ sensitization, inotropic effect, PDE III inhibition, electrophysiological effects) and similar toxicity profiles. The compound has high oral bioavailability in dogs, a favorable safety margin, and no mutagenic potential. Its unique profile—positive inotropy without positive chronotropy, combined with mild vasodilation and class III antiarrhythmic action—makes it a promising candidate for treatment of congestive heart failure. [1]

C18H20N4O2

324.3770

324.158

217963-18-3

9818684

Light yellow to yellow solid powder

1.3±0.1 g/cm3

1.659

0.15

2

5

4

24

581

0

O([H])C([H])(C1C([H])=C([H])C(C#N)=C([H])C=1[H])C([H])([H])N1C([H])([H])C([H])=C(C2C([H])([H])C([H])([H])C(N([H])N=2)=O)C([H])([H])C1([H])[H]

BPEKLIDKLJZYOX-UHFFFAOYSA-N

InChI=1S/C18H20N4O2/c19-11-13-1-3-15(4-2-13)17(23)12-22-9-7-14(8-10-22)16-5-6-18(24)21-20-16/h1-4,7,17,23H,5-6,8-10,12H2,(H,21,24)

4-[1-hydroxy-2-[4-(6-oxo-4,5-dihydro-1H-pyridazin-3-yl)-3,6-dihydro-2H-pyridin-1-yl]ethyl]benzonitrile

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)