The hydrolysis kinetics of monobasic and dibasic aminoalkyl esters of ketorolac

Prodrugs of NSAIDs: A Review

INTORODUCTION

Prodrug approach deals with chemical biotransformation or enzymatic conversion or involves inactive or less active bio-reversible derivatives of active drug molecules. They have to pass through enzymatic or chemical biotransformation before eliciting their pharmacological action.

METHODS & MATERIALS

The two different pharmacophores combine to give synergistic activity or may help in targeting the active drug to its target. Prodrug super seeds the problems of prodrug designing, for example solubility enhancement, bioavailability enhancement, chemical stability improvement, presystemic metabolism, site specific delivery, toxicity masking, improving patient acceptance, or eradicating undesirable adverse effects.

RESULTS

As an outcome the search for a prodrug or mutual prodrug with reduced toxicity has continued during recent years. This present review emphasizes the common help to revamp physiochemical, pharmaceutical and therapeutic effectiveness of drugs.

CONCLUSION

This gives the researcher a common platform where they can find prodrugs of commonly used NSAIDs to overcome the gastrointestinal toxicity (irritation, ulcergenocity and bleeding).

Equilibria, kinetics and mechanism for the degradation of the cytotoxic compound L-NG-nitroarginine

L-N^G-nitroarginine (LNNA), an analog of L-arginine, is a competitive inhibitor of nitric oxide synthase which causes the selective reduction of blood flow to tumor cells. Despite the potential of LNNA to function as an adjuvant in cancer therapies, its poor solubility and stability have hindered the development of an injectable formulation of LNNA that is suitable for human administration. This work, for the first time, details a systematic study on the determination of equilibrium K_a constants and the rate law of LNNA degradation. The four K_a values of LNNA were determined to be 1.03, 1.10 × 10^-2, 2.51 × 10^-10, and 1.33 × 10^-13 M. From the kinetic and equilibrium studies, we have shown that the deprotonated form of LNNA is the main form of LNNA that undergoes degradation in aqueous media at room temperature. The rate law of LNNA degradation was found to be first order with respect to OH^- concentration and first order with respect to LNNA^- concentration. The rate constant at 25 °C and 1 atm was determined to be 0.04453 M^-1min^-1. A base catalyzed mechanism of LNNA degradation was proposed based on the kinetic study. The mechanism was found to be very useful in explaining the discrepancies and changes of the rate law at different pH values. It is thus recommended that LNNA should be formulated as a concentrated solution in acidic conditions for maximum chemical stability during storage and be diluted with a basic solution to near physiological pH just before administration.

Stability of penethamate, a benzylpenicillin ester prodrug, in oily vehicles

Penethamate (PNT) is an ester prodrug of benzylpenicillin which is marketed as dry powder for reconstitution with aqueous vehicle prior to injection. The purpose of this paper was to investigate the chemical stability of PNT in oily formulations to provide a basis for a ready-to-use (RTU) oil-based PNT formulation. The chemical stability of PNT solutions and suspensions in light liquid paraffin (LP), medium chain triglyceride (MIG), ethyl oleate (EO) and sunflower oil (SO) was investigated at 30 °C. Solid state stability of PNT powder and stability of PNT in EO suspensions with different moisture contents were also evaluated. The solubility of PNT in the oils was in order SO > EO > MIG > LP. Degradation of PNT was rapid in oily solutions and less than 10% remained after 7-15 days. Stability of PNT decreased with increase in moisture content in ethyl oleate suspensions. PNT was stable over four weeks in the solid state. Hydrolysis, due to moisture in the oil formulation is not the only degradation mechanism. PNT stability (% drug remaining) in oily suspensions after 3.5 months was in the order LP (96.2%) > MIG (95.4%) > EO (94.1%) > SO (86%). A shelf-life of up to 5.5 years at 30 °C may be achieved for PNT suspension in these oils.