A Review on Current COVID-19 Vaccines and Evaluation of Particulate Vaccine Delivery Systems

First detected in Wuhan, China, a highly contagious coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), also known as COVID-19, spread globally in December of 2019. As of 19 September 2021, approximately 4.5 million people have died globally, and 215 million active cases have been reported. To date, six vaccines have been developed and approved for human use. However, current production and supply capabilities are unable to meet global demands to immunize the entire world population. Only a few countries have been able to successfully vaccinate many of their residents. Therefore, an alternative vaccine that can be prepared in an easy and cost-effective manner is urgently needed. A vaccine that could be prepared in this manner, as well as can be preserved and transported at room temperature, would be of great benefit to public health. It is possible to develop such an alternative vaccine by using nano- or microparticle platforms. These platforms address most of the existing vaccine limitations as they are stable at room temperature, are inexpensive to produce and distribute, can be administered orally, and do not require cold chain storage for transportation or preservation. Particulate vaccines can be administered as either oral solutions or in sublingual or buccal film dosage forms. Besides improved patient compliance, the major advantage of oral, sublingual, and buccal routes of administration is that they can elicit mucosal immunity. Mucosal immunity, along with systemic immunity, can be a strong defense against SARS-CoV-2 as the virus enters the system through inhalation or saliva. This review discusses the possibility to produce a particulate COVID vaccine by using nano- or microparticles as platforms for oral administration or in sublingual or buccal film dosage forms in order to accelerate global vaccination.

Sublingual Diffusion of Epinephrine Microcrystals from Rapidly Disintegrating Tablets for the Potential First-Aid Treatment of Anaphylaxis: In Vitro and Ex Vivo Study

For the first-aid treatment of anaphylaxis, epinephrine (Epi) 0.3 mg intramuscular (IM) injection in the thigh is the drug of choice. Epi auto-injectors are widely recommended for anaphylaxis treatment in community settings but not necessarily carried or used as prescribed when anaphylaxis occurs. We therefore developed rapidly disintegrating sublingual tablets (RDSTs) as an alternative noninvasive dosage form. Our objective in this study was to evaluate the effect of reducing Epi particle size on its in vitro and ex vivo diffusion, with the goal of enhancing Epi sublingual absorption from Epi RDSTs. Epi particle size was reduced by top-bottom technique using a microfluidizer for one pass at 30,000 Psi. The micronized Epi crystals (Epi-MC) were characterized using Zetasizer, Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Epi RDSTs were formulated and manufactured using our previously developed method. In vitro and ex vivo diffusion of Epi 10, 20, and 40 mg RDSTs and Epi-MC 10 and 20 mg RDSTs (n = 4) were evaluated using Franz cells. Epi 10 mg solution was used as a control. Mean (±standard deviation (SD)) Epi particle size was successfully reduced from 131.8 ± 10.5 to 2.5 ± 0.4 μm. Cumulative Epi diffused and influx from 40 mg Epi RDSTs and 20 mg Epi-MC RDSTs were not significantly different from each other in vitro and ex vivo (p > 0.05). Also, Epi permeability from 20 mg Epi-MC RDSTs was significantly higher than from the rest (p < 0.05). Epi-MC RDSTs improved Epi diffusion twofold and might have the potential to reduce the Epi dose needed in RDSTs by 50%.

Effect of lipid viscosity and high-pressure homogenization on the physical stability of "Vitamin E" enriched emulsion

Recently there has been a growing interest in vitamin E for its potential use in cancer therapy. The objective of this work was therefore to formulate a physically stable parenteral lipid emulsion to deliver higher doses of vitamin E than commonly used in commercial products. Specifically, the objectives were to study the effects of homogenization pressure, number of homogenizing cycles, viscosity of the oil phase, and oil content on the physical stability of emulsions fortified with high doses of vitamin E (up to 20% by weight). This was done by the use of a 27-run, 4-factor, 3-level Box-Behnken statistical design. Viscosity, homogenization pressure, and number of cycles were found to have a significant effect on particle size, which ranged from 213 to 633 nm, and on the percentage of vitamin E remaining emulsified after storage, which ranged from 17 to 100%. Increasing oil content from 10 to 20% had insignificant effect on the responses. Based on the results it was concluded that stable vitamin E rich emulsions could be prepared by repeated homogenization at higher pressures and by lowering the viscosity of the oil phase, which could be adjusted by blending the viscous vitamin E with medium-chain triglycerides (MCT).

Fast-Disintegrating Sublingual Epinephrine Tablets: Effect of Tablet Dimensions on Tablet Characteristics

The purpose of this study was to evaluate the effect of changing dimensions on the hardness (H), disintegration time (DT), and wetting time (WT) of fast-disintegrating epinephrine tablets for sublingual administration as potential first aid treatment for anaphylaxis. Tablet formulations I and II, containing 0% and 10% epinephrine bitartrate, respectively, and weighing 150 mg were prepared by direct compression. Formulations were compressed at a range of forces using an 8/32'' die with concave punches (CP); a 10/32'' and an 11/32'' die with CP and flat punches (FP). Tablet weight variation, content uniformity, thickness, H, DT, and WT were measured. The 8/32'', 10/32'', and 11/32'' dies resulted in tablet thickness of ranges 0.25-0.19'', 0.17-0.1'', and 0.16-0.08'', respectively. The DT and WT using the 8/32'' die were<or=10 and<or=30 sec, respectively, at H<or=5.4+/-0.2 kg for formulation I, and H<or=5.4+/-0.3 kg for formulation II. The DT and WT were<or=10 and<or=30 sec, respectively, using 10/32'' die/CP, 10/32'' die/FP, 11/32'' die/CP, and 11/32'' die/FP at H<or=6.2+/-0.6 kg, <or=6.8+/-0.4 kg, <or=4.9+/-0.1 kg, and<or=7.2+/-0.3 kg, respectively, for formulation I. For formulation II, the DT and WT were<or=10 sec and<or=30 sec, respectively, when H<4 kg. No difference in DT and WT was observed between concave and flat tablets. The 11/32'' and 10/32'' dies resulted in more ideal tablet dimensions for sublingual administration, but H must be maintained<4 kg to ensure rapid DT and WT.

Fast-disintegrating sublingual tablets: effect of epinephrine load on tablet characteristics

The aim of this study was to evaluate the effect of increasing epinephrine load on the characteristics of fast-disintegrating sublingual tablets for the potential emergency treatment of anaphylaxis. Four tablet formulations, A, B, C, and D, containing 0%, 6%, 12%, and 24% of epinephrine bitartrate, respectively, and microcrystalline cellulose:low-substituted hydroxypropyl cellulose (9:1), were prepared by direct compression, at a range of compression forces. Tablet weight variation, content uniformity, hardness, disintegration time, wetting time, and friability were measured for each formulation at each compression force. All 4 tablet formulations at each compression force were within the United States Pharmacopeia (USP) limits for weight variation and content uniformity. A linear increase in compression force resulted in an exponential increase in hardness for all formulations, a linear increase in disintegration and wetting times of A, and an exponential increase in disintegration and wetting times of B, C, and D. At a mean +/- SD hardness of > or = 2.3 +/- 0.2 kg, all tablet formulations passed the USP friability test. At a mean +/- SD hardness of < or = 3.1 +/- 0.2 kg, all tablet formulations resulted in disintegration and wetting times of <10 seconds and <30 seconds, respectively. Tablets with drug loads from 0% to 24% epinephrine can be formulated with hardness, disintegration times, and wetting times suitable for sublingual administration.

Sublingual epinephrine tablets versus intramuscular injection of epinephrine: Dose equivalence for potential treatment of anaphylaxis

BACKGROUND

Epinephrine autoinjectors are underused in the emergency treatment of anaphylaxis in the community, perhaps in part because of fear of needles.

OBJECTIVES

To determine the sublingual epinephrine dose from a novel fast-disintegrating tablet required to achieve epinephrine plasma concentrations (EPPCs) similar to those obtained after epinephrine 0.3 mg intramuscular injection.

METHODS

In a prospective 5-way crossover study, sublingual tablets containing epinephrine 0, 10, 20, and 40 mg, and epinephrine 0.3 mg intramuscular in the thigh (EpiPen) were compared in a validated rabbit model. Blood samples were collected before dosing and 5, 10, 15, 20, 30, 40, 60, 90, 120, 150, and 180 minutes afterward. EPPCs were measured by using high-performance liquid chromatography-electrochemical detection. Pharmacokinetic parameters were calculated by using WinNonlin.

RESULTS

The area under the curve (AUC), maximum concentration (C(max)), and time at which C(max) was achieved (T(max)) did not differ significantly (P > .05) after epinephrine 40 mg (AUC = 1861 +/- 537 ng/mL/min, C(max) = 31.0 +/- 13.1 ng/mL, and T(max) = 9 +/- 2 minutes) and epinephrine 0.3 mg intramuscular (AUC = 2431 +/- 386 ng/mL/min, C(max) = 50.3 +/- 17.1 ng/mL, and T(max) = 21 +/- 5 minutes). The AUC after tablets containing epinephrine 0 mg (AUC = 472 +/- 126 ng/mL/min), epinephrine 10 mg (AUC = 335 +/- 152 ng/mL/min), and epinephrine 20 mg (AUC = 801 +/- 160 ng/mL/min) did not differ significantly from each other, but were significantly lower (P < .05) than the AUC after epinephrine 0.3 mg intramuscularly.

CONCLUSION

Sublingual administration of epinephrine 40 mg from this tablet formulation resulted in EPPCs similar to those obtained after epinephrine 0.3 mg intramuscular injection in the thigh.

CLINICAL IMPLICATIONS

For treatment of anaphylaxis in the community, self-injectable epinephrine is underused. This novel, fast-disintegrating epinephrine tablet formulation for sublingual administration is a feasible alternative that warrants further development.

Epinephrine for the treatment of anaphylaxis: do all 40 mg sublingual epinephrine tablet formulations with similarin vitro characteristics have the same bioavailability?

Epinephrine autoinjectors are underutilized in the first aid emergency treatment of anaphylaxis in the community; so non-invasive sublingual epinephrine administration is being proposed. In order to determine the effect of changing excipients on the bioavailability of sublingual epinephrine, four distinct fast-disintegrating epinephrine 40 mg tablet formulations, A, B, C and D, were manufactured using direct compression. All formulations were evaluated for tablet hardness (H), disintegration time (DT) and wetting time (WT). In a prospective 5-way crossover study, four sublingual formulations and epinephrine 0.3 mg i.m. as a control were tested sequentially in a validated rabbit model. Blood samples were collected before dosing and at intervals afterwards. Epinephrine plasma concentrations were measured using HPLC-EC. All tablet formulations met USP standards for weight variation and content uniformity, and resulted in similar mean H, DT and WT (n=6). The area under the curve (AUC), maximum concentration (C(max)) and time at which C(max) was achieved (T(max)) did not differ significantly after the sublingual administration of formulation A and epinephrine 0.3 mg i.m. The AUC after B, C and D were significantly lower (p<0.05) than after epinephrine 0.3 mg i.m. These results suggest that the selection of excipients used in these tablet formulations can affect the bioavailability of sublingually administered epinephrine.