New antiarrhythmic agents. 7. 2,3-Diaminopropionanilides.

A series of 2,3-diaminopropionanilides was synthesized by acylation of mono- and disubstituted aniline derivatives with 2,3-dibromopropionyl chloride and subsequent amination with the appropriate secondary amines. The target compounds were evaluated in mice for antiarrhythmic efficacy against chloroform-induced tachycardia and for central nervous system toxicity. Several of the active agents were found to have much higher antiarrhythmic potencies than lidocaine, but they were also toxic. Evaluation of the target compounds for local anesthetic activity in the form of sciatic nerve block in rats showed that most compounds had durations of block similar to that of lidocaine; none exhibited the long duration of block seen with etidocaine.

New antiarrhythmic agents. 6. Quantitative structure-activity relationships of aminoxylidides.

The synthesis and pharmacological evaluation of primary and tertiary aminoxylidides with the amino group in the 2-7 position of the acyl chain are described. 2,6-Xylidine was acylated with haloacyl halides and converted to the target compounds by direct amination or by the Gabriel procedure. Alternatively, 2,6-xylidine was coupled with keto acids, and the ketoxylidides were converted to the amines by reductive amination. The target compounds were evaluated in mice both for antiarrhythmic efficacy against chloroform-induced tachycardia and for central nervous system toxicity. Experimentally determined values of partition coefficients and pKa values were used for quantitative structure-activity analyses. While the antiarrhythmic activity could be described as a function of log P alone, the CNS toxicity was best described as a function of both log P and pKa. The results suggest that antiarrhythmic potency can be increased by increasing lipophilicity, while the therapeutic index can be improved by increasing the pKa.

Synthesis of alkylaminoalkylamides of substituted 2-aminopyrroles as potential local anesthetic and antiarrhythmic agents. II: beta-Amines.

The synthesis, local anesthetic and antiarrhythmic properties, and CNS toxicity of 14 2-(3-alkylaminoalkylamido)-pyrroles are described. Most of the compounds exhibited local anesthetic activity by the guinea pig wheal test, with seven showing comparable or greater activity than lidocaine. Most compounds also exhibited antiarrhythmic activity; three compounds had more potent activity than lidocaine. All compounds exhibiting antiarrhythmic activity also were toxic to the CNS. However, two of the three compounds having greater activity than lidocaine possessed more desirable therapeutic indexes.

Synthesis of alkylaminoalkylamides of substituted 2-aminopyrroles as potential local anesthetic and antiarrhythmic agents I: alpha-Amines.

The synthesis, local anesthetic and antiarrhythmic properties, and CNS toxicity of 19 2-(2-alkylaminoalkylamido)pyrroles are described. Most of the compounds exhibited local anesthetic activity by the guinea pig wheal test, and four showed activity comparable to or greater than that of lidocaine. Most compounds also exhibited antiarrhythmic activity; five compounds had activity comparable to that of lidocaine, and one was more potent. All compounds exhibiting antiarrhythmic activity also were toxic to the central nervous system.

New antiarrhythmic agents. 4. 1'-(Aminoalkyl)-1,2,3,4-tetrahydronaphthalene-1-spiro-3'-pyrrolidine-2',5'-dione derivatives.

A series of 33 1'-(Aminoalkyl)-1,2,3,4-tetrahydronaphthalene-1-spiro-3'-pyrrolidine-2',5'-dione derivatives was tested for antiarrhythmic and toxic effects in mice and dogs. In mice, 31 compounds produced some protection against chloroform-induced tachyarrhythmias at subcutaneous doses of 100 mg/kg, and 6 compounds produced no detectable toxicity at doses protecting 80% or more of the animals. Seven of the more potent and nontoxic derivatives were tested in dogs with surgically induced myocardial infarctions. All produced distinct antiarrhythmic effects at doses considerably lower than doses of lidocaine or tocainide producing comparable effects. The principal toxic effects observed in dogs were convulsion and depression of intracardiac conduction; they occurred generally at higher doses than those leading to antiarrhythmic effect. Several compounds also suppressed digitalis-induced arrhythmias in anesthetized dogs. Half-lives and total body clearance in dogs were determined for three compounds; two had half-lives comparable to that of tocainide, a long-acting, orally active antiarrhythmic agent, in clinical trials.

New antiarrhythmic agents. 5. alpha-Aminoaceto-2,6-xylidides with functionalized amide alkyl substituents.

The synthesis of aminoaceto-2',6'-xylidides substituted on the amide nitrogen with 2-(diethylamino)ethyl, 2-aminoethyl, 2-hydroxyethyl, and 2-ethoxyethyl groups is described. The 2-aminoethyl derivatives were prepared by treatment of N-(2-phthalimidoethyl)-2',6'-xylidine with chloroacetyl chloride, followed by treatment with either potassium phthalmide or diethylamine. Hydrazinolysis of the phthalimides liberated the free amines. The remaining target compounds were produced by alkylation of lidocaine or of 2-phthalimidoaceto-2',6'-xylidide with the appropriate halide and sodium hydride, followed by hydrazinolysis where necessary. All target compounds were evaluated for antiarrhythmic efficacy against chloroform-induced ventricular tachycardia, as well as for acute CNS toxicity in mice. Most of the target compounds were more potent than the corresponding secondary amides and had improved therapeutic margins toward CNS toxicity. The diamines N-(2-aminoethyl)-2-aminoaceto-2',6'-xylidide (13) and N-(2-aminoethyl)--2-(diethylamino)aceto-2',6'-xylidide (29) are especially promising in this respect. Several compounds were tested as spinal anesthetics.

Tocainide conjugation in humans: novel biotransformation pathway for a primary amine.

The metabolism of tocainide, an experimental antiarrhythmic drug, was studied in humans. Urinary excretion of unchanged drug was 28-55% in 24 hr after oral dosing. Urine hydrolysis with hydrochloric acid or beta-glucuronidase increased tocainide recovery to 55-79%. Saccharo-1,4-lactone inhibited the beta-glucuronidase-mediated tocainide recovery increase. Adjustment of urine to pH 13 produced a compound identified as 3-(2,6-xylyl)-5-methylhydantoin. Evidence suggests that it was derived from the same metabolite that formed the additional tocainide after acid or beta-glucuronidase treatment. Tocainide carbamoyl O-beta-D-glucuronide is the structure proposed for the metabolite. The suggested pathway for its formation involves the addition of carbon dioxide to the amino nitrogen of tocainide followed by uridine diphosphate-glucuronic acid conjugation.

New antiarrhythmic agents. 1. Primary alpha-amino anilides.

Thirty-two alpha-amino anilides with various substituents in the aromatic ring and in the alpha position are described. Their abilities to protect mice against chloroform-induced fibrillation and to elicit toxicity were determined. Substitution of an alkyl or aryl group in the alpha position enhanced the antifibrillatory activity. In most cases, increased potency was accompanied by increased toxicity. Eleven compounds were tested in dogs with surgically induced myocardial infarction; most showed antiarrhythmic activity. 2-Aminopropiono-2',6'-xylidide, tocainide, was chosen for clinical investigation.

New antiarrhythmic agents. 2. Amide alkyl alpha-amino xylidides.

The synthesis of a series of N-alkyl 2-amino 2',6'-xylidides is described. The method involved coupling of the N-alkyl-2',6'-xylidine with the appropriate 2-haloacyl halide, followed by ammonolysis. Alternatively, alkylation of the 2-phthalimido 2',6'-xylidide with NaH and the alkyl halide followed by hydrazinolysis was used. All compounds were evaluated for their ability to protect mice against chloroform-induced ventricular fibrillation. The compounds were generally more potent antifibrillatory agents than the corresponding secondary amides. All were more potent than tocainide and several showed less CNS toxicity. Five compounds were further evaluated in dogs with ventricular arrhythmias resulting from myocardial infarction. N-Ethyl-2-aminoaceto-4'-propoxy-2',6'-xylidide was as potent as lidocaine and produced less CNS toxicity.

New antiarrhythmic agents. 3. Primary beta-amino anilides.

The synthesis and pharmacologic evaluation of primary beta-amino anilides, as well as comparisons with tocainide, lidocaine, and its beta homologue, are described. Substituted anilines were acylated with 3-bromoacyl chlorides and converted to the title compounds by direct amination or via 3-phthalimido anilides and subsequent hydrazinolysis. Alternatively, anilines were acylated with substituted acryloyl chlorides and the amines prepared by addition of ammonia to the double bond. The target compounds were evaluated for their ability to protect against chloroform-induced fibrillation in mice. All were found to have some antifibrillatory activity; several were more potent than tocainide, a compound in clinical trials as an oral antiarrhythmic drug. Four compounds were tested for their effects against ventricular arrhythmias in dogs with myocardial infarction. 3-Amino-2',6'-butyroxylidide (38) was found to be more potent and less CNS toxic than tocainide.