Deterioration of nitroglycerin tablets

Inhibiting Sublimation of Thymol by Cocrystallization

A thymol:4,4'-dipyridyl (2:1) cocrystal (Form I) is reported to suppress thymol sublimation. The cocrystal was prepared via solution-mediated phase transformation and its structure is sustained by O-H (phenol) ··· N (pyridyl) hydrogen bonds between two individual components. A cocrystal polymorph (Form II) was formed via solid state transformation or via vapor phase upon heating. Using gravimetry analysis, it was demonstrated that cocrystal Form I decreased the sublimation rate of thymol by 38-fold. This study demonstrates that cocrystallization is an effective approach to reduce vapor pressure and sublimation of solids, thus achieving odor-masking.

Open-Label Study of the Stability of Sublingual Nitroglycerin Tablets in Simulated Real-Life Conditions

Contemporary practice favors refilling sublingual nitroglycerin (SL NTG) every 3 to 6 months. This recommendation is based on antiquated data that does not consider the reformulated tablet and the improved manufacturing process. Our objective was to investigate the stability of SL NTG over time using simulated real-life scenarios in comparison to controlled storage conditions. This was an open-label study of 100- and 25-count commercial SL NTG bottles stored in either controlled temperature and relative humidity conditions, or carried in a pocket or purse. SL NTG potency (chemical stability) was assessed using high performance liquid chromatography and physical stability was assessed by changes in tablet weights over time through the labeled expiration date. Both chemical and physical stability of SL NTG were affected by environmental and physical factors. High temperature storage resulted in the most rapid loss of potency. Tablets carried in a pant pocket lost potency faster than those carried in a purse. Potency was also dependent on headspace of the bottle. Tablets stored in the original bottle in a temperate environment could be expected to maintained potency for more than 2 years when carried in a purse, irrespective of package size. When carried in a pant pocket, potency of a 25-count bottle was maintained for 2 years, whereas potency of a 100-count bottle fell below acceptable limits at 12 months. In conclusion, since potency is dependent on temperature, headspace, and carrying practices, frequency of SL NTG refills should be based on individual patient behavior.

Environmental temperature variations cause degradations in epinephrine concentration and biological activity

This study determined the biological consequence of temperature induced epinephrine degradation. Two different epinephrine preparations (1:1,000 and 1:10,000) were exposed to either cold (5 degrees C) or hot (70 degrees C) temperature. The exposure occurred for 8-hour periods each day in 4-, 8-, and 12-week intervals. Samples and identical controls were then chemically evaluated using high-pressure liquid chromatography (HPLC), and biological activity of samples showing chemical degradation was assessed in conscious rats. Epinephrine (1:10,000) underwent a significant degradation and a loss of concentration of the parent compound after 8 weeks of heat treatment. By 12 weeks, 64% of the epinephrine was degraded. A smaller (30%) but significant loss of cardiovascular potency was determined by blood pressure and heart rate responses in conscious rats. The degradation of epinephrine (1:1,000) was not statistically significant even after 12 weeks of heat exposure. No change was noted from control in either epinephrine concentration when exposed to cold temperatures. In conclusion, epinephrine (1:10,000) deteriorates in the presence of elevated temperature and should be protected from high temperatures when carried by EMS providers. The degradation products may possess biological activity.

Sublingual nitroglycerin. I. Comparative evaluation of the physical stability of commercially available tablets

The physical stability of one type of stabilized molded and three types of compressed nitroglycerin tablets was studied. The evaporation rate of nitroglycerin was controlled by its vapour pressure and by the matrix effect of the dosage forms. The four products showed different vapour pressures and matrix effects. In time nitroglycerin escapes from the outmost layers of the tablets; the dosage form in which the drug showed the lowest vapour pressure (the stabilized molded tablet) was found to be the most stable one. However, from the time when the drug had escaped from the outmost layers of the dosage form, the matrix effect became dominant. When nitroglycerin tablets were stored in tightly closed containers at room temperature potency loss was minimal. Even when the bottles were opened regularly this did not result in a significant loss of the drug. Measures are suggested to minimize drug evaporation.

The stability of glyceryl trinitrate tablets during patient use

The stability of glyceryl trinitrate (GTN) tablets stored in ways commonly used by patients was investigated to enable pharmacists and physicians to give better advice about tablet storage. Analysis of 43 samples of tablets collected from hospital patients showed that the GTN content of these samples differed significantly from that of fresh tablets. Tablets kept in the manufacturer's bottle contained significantly more GTN than those transferred to other airtight vials (p less than 0.05) or pill boxes (p less than 0.005). The content of GTN was also significantly lower in tablets stored in pill boxes compared with other vials (p less than 0.01). Similar trends were found when tablets were stored in glass or plastic vials, pill boxes or were left exposed to air in the laboratory. These results emphasize that the best way to store GTN tablets is in the manufacturer's container. However, since many patients find that this bottle is awkward and inconvenient, a suitable alternative would be to carry a few tablets in a small airtight container (preferably glass). The unused tablets should be discarded every two weeks and nothing else should be added to the container. The use of pill boxes should be strongly discouraged.

Pharmaceutical considerations of nitroglycerin

During the past few years, there have been rapid changes in the pharmaceutical uses of nitroglycerin. New dosage forms and new delivery systems have become available, which have resulted in potential confusion to all concerned with the proper use of these systems. The goal of this review is to prevent confusion and to bring all the relevant information together. The various analytical techniques available for quality control of the dosage forms and for the study of the pharmacokinetics are reviewed, with the intent of enabling the reader to identify pertinent references rapidly. The interaction of nitroglycerin with packaging and plastic delivery devices is also reviewed so that the reader can make informed choices. Finally, the clinical pharmacy and pharmacokinetics are reviewed so as to bring the reader up to date in that area. After reading this article, the areas of nitroglycerin research that still need to be explored should be apparent.

Stability of intravenous nitroglycerin solutions

The stability of intravenous nitroglycerin solutions prepared from either sublingual tablets or a 10% nitroglycerin-lactose adsorbate (powder) was examined under various conditions. Nitroglycerin concentration was measured by high-pressure liquid chromatography. Nitroglycerin stock solutions (0.8-1.0 mg/ml) prepared from tablets or powder in either 0.9% saline were stored upright in refrigerated multidose vials for 6 months without a significant decrease in concentration. Storage of the solutions at room temperature resulted in a 20% loss after 3 months. Intravenous nitroglycerin solutions (0.2 mg/ml) prepared from tablets or powder in 0.9% saline or 5% dextrose in water were stored in glass intravenous bottles at temperatures between 6 and 38 degrees for 24 hr with a maximum loss of 18%. Stability was not affected by light. Solutions in contact with rubber stoppers, plastic intravenous bags, or plastic administration sets exhibited decreased nitroglycerin concentration characteristic of sorption. Nitroglycerin concentrations decreased to a greater extent when the administration sets were equipped with plastic burets. Brief contact of nitroglycerin solutions with a plastic syringe did not result in decreased concentration. The stability of intravenous nitroglycerin solutions packaged in glass was not dependent on light, the vehicle, or the source of nitroglycerin. Contact with rubber or plastic surfaces should be minimized.

Loss of nitroglycerin from aqueous solution into plastic intravenous delivery systems

The mechanism of potential loss of nitroglycerin stored in plastic and glass containers was studied from an equilibrium and kinetic approach. Plastic strips equilibrated with dilute aqueous solutions of neat nitroglycerin showed that the drug was lost by absorption. Drug loss was followed by an electron-capture GLC assay. The same assay of control solutions in glass showed no drug loss in 48 hr at pH 5.7. The kinetics of nitroglycerin absorption and desorption were determined using synthesized 14C-labeled drug. Absorption can be quantified using a diffusion model, where the concentration in the aqueous phase falls with time. Curve fitting yielded an average diffusion coefficient in plastic of 2.05 x 10(-9) cm2/sec and a partition coefficient of 104 (plastic-water) at 30 degrees. Temperature-dependence studies of absorption showed that the diffusion coefficient followed an Arrhenius relationship with an energy requirement of 19.6 kcal/mole, whereas effects on the partition coefficient were negligible. Nitroglycerin desorption from plastic disks under sink conditions into water can be quantified by assuming a diffusion model where the concentration at the surface of a plane sheet remains constant. Nonlinear least-squares curve fitting generated a diffusion coefficient of 1.14 x 10(-9) cm2/sec for the desorption process at 30 degrees.

Polymer sorption of nitroglycerin and stability of molded nitroglycerin tablets in unit-dose packaging

The sorption of nitroglycerin by thermoplastic polymers and the stability of molded nitroglycerin tablets in strip packaging were studied. The polymers investigated varied greatly in their affinity for nitroglycerin, the order of decreasing affinity being: vinyls greater than low density polyethylene greater than ionomers greater than high density polyethylene. With the proper choice of packaging, molded nitroglycerin tablets stabilized with povidone maintained acceptable potency for up to 2 years at 26 degrees when strip packaged in unit doses. Chemical decomposition (hydrolysis) of nitroglycerin also was investigated. Povidone accelerated the decomposition of nitroglycerin; at high temperature, decomposition was a significant factor in tablet stability for tablets containing povidone.