A Novel, Optimized Method to Accelerate the Preparation of Injectable Poly-L-Lactic Acid by Sonication

Current consensus for preparing injectable poly-L-lactic acid (PLLA) suggests adequate hydration (less than equal to 2-24 hours of reconstitution) of the lyophilized particles before injection, but the volume of reconstitution and the duration of hydration time varies. This study established a method to evaluate the distribution of PLLA particles after hydration and found that longer hydration time increased the effective portion (particles less than 60 μm) of PLLA products. Further investigation of the feasibility of reconstitution with sonication revealed that 2-hour hydration of PLLA powders with additional 5-minute-sonication could yield a comparable particle distribution with 48-hour-hydration of PLLA. Moreover, adding lidocaine into the diluent did not alter the distribution of PLLA particles. We proposed a new, feasible and efficient method of preparing PLLA injectable products: 2-hour hydration of the powders, sonication of the bottle or vial containing PLLA products for at least 5 minutes, and finalization with 1-2 mL of lidocaine immediately before injection. J Drugs Dermatol. 2018;17(8):894-898.

Polymeric complexes of lidocaine hydrochloride with poly(acrylic acid) and poly(2-hydroxyethyl vinyl ether)

The specific interactions of local anesthetic lidocaine hydrochloride with poly(acrylic acid) and poly(2-hydroxyethyl vinyl ether), as well as in a triple system composed of the drug and both polymers, have been studied in aqueous solutions by viscometric, turbidimetric, potentiometric, and FTIR spectroscopic methods. The mechanism of the drug binding to the polymers and the structures of the polycomplexes formed are clarified.

Bioreversible quaternary N-acyloxymethyl derivatives of the tertiary amines bupivacaine and lidocaine—synthesis, aqueous solubility and stability in buffer, human plasma and simulated intestinal fluid

Design of water-soluble prodrugs may constitute a means to improve the oral bioavailability of drugs suffering from dissolution rate-limited absorption. The model drug bupivacaine containing a tertiary amine function has been converted into bioreversible quaternary N-acyloxymethyl derivatives. The pH-independent solubility of the N-butanoyloxymethyl derivate exceeded 1000 mg ml-1 corresponding approximately to a 10,000-fold increase in water solubility compared to that of bupivacaine base. The kinetics of hydrolysis of the prodrugs was studied in the pH range 0.1-9.8 (37 degrees C). Decomposition was found to follow first-order kinetics and U-shaped pH-rate profiles were constructed. The observed differences between the hydrolytic lability of the derivatives might most likely be ascribed to steric effects. In most cases, the prodrugs were quantitatively converted into bupivacaine. However, for the hydrolysis of the N-butanoyloxymethyl derivative at neutral to slightly alkaline pH parallel formation of bupivacaine (approximately 80%) and an unknown compound X (approximately 20%) was observed. LC-MS analysis of the latter compound suggests that an aromatic imide structure has been formed from an intramolecular acyl transfer reaction involving a nucleophilic attack of the amide nitrogen atom on the ester carbonyl carbon atom. Whereas the derivatives were poor substrates for plasma enzymes; they were hydrolyzed rapidly to parent bupivacaine in the presence of pancreatic enzymes (simulated intestinal fluid) at 37 degrees C. The data indicate that such prodrugs possess sufficient stability in the acidic environment of the stomach to reach the small intestine in intact form where they can be cleaved efficiently by action of pancreatic enzymes prior to drug absorption. Thus, the N-acyloxymethyl approach might be of potential utility to enhance oral bioavailability of tertiary amines exhibiting pKa values below approximately 6 and intrinsic solubilities in the low microM range.

Characterization of cellulosic hot-melt extruded films containing lidocaine

Hot-melt extrusion technology was used to produce thin films containing a model drug, lidocaine, and the cellulosic polymers hydroxypropyl cellulose (HPC) and hydroxypropyl methyl cellulose (HPMC). Two film formulations were extruded and compared, one containing only HPC and the other containing HPC:HPMC (80:20). Thermal analysis of the films using differential scanning calorimetry (DSC) suggested that the drug existed in the amorphous condition, which was confirmed by wide angle X-ray diffractometry. Sustained release of the drug was observed from both of the polymer matrices. Dissolution profiles suggested that HPMC retarded the drug release from HPC:HPMC (80:20) films. However, the mechanism of drug release from both of the films was predominantly diffusion of the drug through the polymer matrices. Incorporation of HPMC also increased both adhesive strength and work of adhesion as compared to the HPC-only films.

Synthesis, structure and pharmacology of acyl-2,6-xylidines

L-2-perhydroheterocyclicalkyl acids were condensed with 2,6-xylidine. 8 new optically active acyl-2,6-xylidines were obtained. Absolute configuration of acyl-2,6-xylidines were selected for pharmacological examinations.

Solid-Phase Synthesis of Lidocaine and Procainamide Analogues Using Backbone Amide Linker (BAL) Anchoring

New solid-phase strategies have been developed for the synthesis of lidocaine (1) and procainamide (2) analogues, using backbone amide linker (BAL) anchoring. Both sets were prepared starting from a common resin-bound intermediate, followed by four general steps: (i) attachment of a primary aliphatic or aromatic amine to the solid support via reductive amination (as monitored by a novel test involving reaction of 2,4-dinitrophenylhydrazine with residual aldehyde groups); (ii) acylation of the resultant secondary amine; (iii) displacement of halide with an amine; and (iv) trifluoroacetic acid-mediated release from the support. A manual parallel strategy was followed to provide 60 novel compounds, of which two dozen have not been previously described. In most cases, initial crude purities were >80%, and overall isolated yields were in the 40-88% range.

Development of polymer film dosage forms of lidocaine for buccal administration: II. Comparison of preparation methods

In previous studies, we prepared film dosage forms of lidocaine (LC) with hydroxypropylcellulose (HPC) as a film base using the solvent evaporation (SE) method. However, from the viewpoint of environmental issues, a reduction in organic solvent use in pharmaceutical and other industries is required. In this study, we prepared the LC films by direct compression of the physical mixture (DCPM method) and direct compression of the spray dried powder (DCSD method). Magnesium stearate, which was required as a lubricant for direct compression, showed no effect on the LC release rate. The LC release rate (%/h) was independent of the compression pressure, but a higher pressure was preferable to easily remove the film from the punches. An increase in the film weight decreased the LC release rate expressed in %/h, whereas no significant effect of film weight was observed on the LC release rate from unit surface area expressed in mg/h/cm(2). The LC release rate (%/h) was independent of the LC content, suggesting that the LC release rate (mg/h) can be quantitatively controlled by changing the LC content in the formulation. The LC release rate and penetration rate were affected by the preparation method; that is, DCPM method < DCSD method < SE method. The LC penetration rates through excised hamster oral mucosa were linearly correlated to the release rate of un-ionized LC, which was estimated by the LC release rate multiplied by the un-ionized fraction of LC for the HPC film dosage form.

Studies on sulfation of synthesized metabolites from the local anesthetics ropivacaine and lidocaine using human cloned sulfotransferases

The metabolism of the local anesthetics lidocaine and ropivacaine (ropi) involves several steps in humans. Lidocaine is mainly hydrolyzed and hydroxylated to 4-OH-2,6-xylidine (4-OH-xyl). The metabolism of ropi, involving dealkylation and hydroxylation, gives rise to 3-OH-ropi, 4-OH-ropi, 3-OH-2'6'-pipecoloxylidide (3-OH-PPX), and 2-OH-methyl-ropi. Because the metabolites are hydroxylated, they are particularly prone to subsequent Phase II conjugation reactions such as sulfation and glucuronidation. This study focused on the in vitro sulfation of these metabolites as well as another suspected metabolite of ropi, 2-carboxyl-ropi. All the metabolites were synthesized for the subsequent enzymatic studies. Five cloned human sulfotransferases (STs) were used in this study, namely, the phenol-sulfating form of ST (P-PST-1), the monoamine-sulfating form of ST (M-PST), estrogen-ST (EST), ST1B2, and dehydroepiandrosterone-ST (DHEA-ST), all of which are expressed in human liver. The results demonstrate that all of the metabolites except 2-OH-methyl-ropi and 2-carboxyl-ropi can be sulfated. It was also found that all of the STs can conjugate the remaining hydroxylated metabolites except DHEA-ST. However, there are large differences in the capacity of the individual human ST isoforms to conjugate the different metabolites. P-PST-1 sulfates 3-OH-PPX, 3-OH-ropi, and 4-OH-xyl; M-PST and EST conjugate 3-OH-PPX, 3-OH-ropi, and 4-OH-ropi whereas ST1B2 sulfates only 4-OH-xyl. The most extensively sulfated ropi metabolite is 3-OH-PPX. In conclusion, all of the hydroxylated metabolites of lidocaine and ropi can be sulfated if the hydroxyl group is attached to the aromatic ring in the metabolites. The human ST enzymes that are considered to be responsible for the sulfation of these metabolites in vivo are P-PST-1, M-PST, EST, and ST1B2. These enzymes are also found in the liver; this is the most important tissue for the metabolism of ropi in humans, demonstrated by.

Pharmacophore and pseudoreceptor modelling of class Ib antiarrhythmic and local anaesthetic lidocaine analogues

A molecular modelling study was carried out in order to investigate the molecular binding behaviour of antiarrhythmically and local anaesthetically active aminoacylanilide derivatives from the lidocaine type at their specific sodium channel binding site. An examination of relevant X-ray structures and of results derived from systematic and random search conformational analyses yielded information about the spatial requirements of these sodium channel blocking compounds. Common structural elements in combination with their non-covalent interaction potentials were used to generate a rational pharmacophore model. To further support and refine this model an atomistic pseudoreceptor of the Na+ channel binding site was constructed using a training set of eight well-defined lidocaine homologues. With the final pseudoreceptor, composed of tyrosine, phenylalanine, serine, valine and three isoleucine residues, it was possible to correlate experimental versus calculated dissociation constants of the training set with a correlation coefficient of 0.98. To test the accuracy of this model, the affinities of three additional compounds, not used for pseudoreceptor modelling, were predicted. After free relaxation within the binding cavity using a Monte-Carlo minimization the test set yielded a RMS error in the prediction of 0.039 kcal/mol corresponding to an uncertainty factor of 1.06. In addition, this hypothetical receptor model provides evidence for an exceptional binding mode of the lidocaine metabolite glycinexylidide (GX) which could explain its low binding affinity and thereby possibly the minor physiological effects with respect to lidocaine.

New antiarrhythmic agents. N-aryl-8-pyrrolizidinealkanamides

The synthesis and antiarrhythmic activity of N-aryl-8-pyrrolizidinealkanamides are described. The target compounds were evaluated for their ability to protect against chloroform-induced fibrillation in mice. Many of them were found to have antifibrillatory activity comparable to that of lidocaine; several are more potent than lidocaine. N-(2,6-Dimethylphenyl)-8-pyrrolizidineacetamide which was found to be more potent and less toxic (LD50) than lidocaine, also showed a long duration of action in dogs with ventricular arrhythmias after oral administration.

Synthesis and vasodepressor screen of a series of 2-(2-alkylaminoalkylamido)-3-carbamyl-4-methyl-5-benzylpyrroles

A series of 2-(2-alkylaminoalkylamido)-3-carbamyl-4-methyl-5-benzylpyrroles was synthesized and screened for vasoactivity. The compounds were administered intraperitoneally as a suspension to approximate the oral route of administration and intravenously when solubilization could be affected with suitable solvents. The most active compound following intravenous or intraperitoneal administration lowered blood pressure 73 and 35.5 mm Hg at doses of 4 mg/kg iv and 100mg/kg ip, respectively. It also exhibited the longest duration of vasodepressor activity (25 min). Several other compounds exhibited vasodepressor activity following intraperitoneal administration. Several hydrochloride salts appeared to be more potent vasoactive agents than the corresponding bases.

Synthesis of substituted 2-aminopyrrole analogs of lidocaine II

The synthesis and local anesthetic and antiarrhythmic properties of eight substituted 2-diethylaminoacetamido-3-carbamyl-4-methylpyrroles are described. Three compounds showed significant local anesthetic activity by the guinea pig wheal test, and four showed antiarrhythmic activity against chloroform-induced ventricular arrhythmias in mice.

Synthesis of substituted 2-aminopyrrole analogs of lidocaine I

The synthesis, local anesthetic, and antiarrhythmic properties of nine 2-diethylaminoacetamido-3-cyano-4-methyl-5-substituted pyrroles are described. All compounds showed local anesthetic activity by the guinea pig wheal test and antiarrhythmic activity for chloroform-induced ventricular arrhythmias in mice.

Improved synthesis of N-(2,6-dimethylphenylcarbamoylmethyl) iminodiacetic acid and analogs

A new synthesis of N-(2,6-dimethylphenylcarbamoyl-methyl)iminodiacetic acid directly from nitrilotriacetic acid was developed. Six analogs also were synthesized. Their technetium Tc 99m complexes were prepared and characterized. Electrophoresis and chromatography were used to determine the radiochemical purity of each complex.

N-Hydroxyamide metabolites of lidocaine. Synthesis, characterization, quantitation, and mutagenic potential

Two possible N-hydroxyamide metabolites of lidocaine were synthesized and characterized. A combined technique utilizing chemical-ionization mass spectrometry and stable isotope labeling demonstrated that these potentially carcinogenic N-hydroxyamides were neither present in human urine after oral lidocaine administration nor during intravenous infusion of lidocaine for the treatment of ventricular arrhythmias. However, small amounts of 2,6-dimethylphenylhydroxylamine were detected in the urine of all subjects. Mutagenesis assays using the Ames test showed that neither the N-hydroxyamides nor the N-hydroxyarylamine produced revertant colonies above background levels using the Salmonella tester strain TA-1538.

99MTc-HIDA, a gallbladder imaging agent: experimental aspects

The molecule N-(2,6-dimethyl-phenyl-carbamoyl-methyl)-iminodiacetic acid (HIDA), capable of chelating reduced 99mTc, was synthesized, characterized, labeled with 99mTc, and studied in experimental animals. The results indicated that the new 99mTc-radiopharmaceutical is rapidly cleared from the blood to the liver, then rapidly removed to the gallbladder and excreted into the duodenum through the common bile duct. A comparative kinetic study of 99mTc-HIDA and 131I-Rose Bengal performed in rabbits demonstrated that both radiopharmaceuticals had a similar blood clearance rate, but cleared at a different rate from liver to gallbladder. 99mTc-HIDA showed a faster accumulation in the gallbladder than 131I-Rose Bengal. These findings, combined with the advantage of the low acute toxicity of HIDA, were promising enough to encourage a further evaluation and clinical investigation of this new Tc-99m hepatobiliary agent.

Tissue distribution of technetium-99m and carbon-14 labeled N-(2,6-dimethylphenylcarbamoylmethyl)iminodiacetic acid

The synthesis, radiochemical labeling, and tissue distribution characteristics of N-(2,6-dimethylphenylcarbamoylmethyl)iminodiacetic acid are described. The radiopharmaceutical prepared by labeling with 99mTc was rapidly eliminated through the hepato-biliary system of mice. Parent 14C compound was eliminated primarily through the kidney. The 99mTc ion appears to have a greater influence than the organic carrier molecule on the distribution of the radiopharmaceutical.