The oral route continues to be the most used method of delivering active pharmaceutical ingredients. There is a growing need for controlled release dosage forms and increased patient compliance. Hydrophilic polymers have been highly employed to control drug release rates. At the same time, developments in manufacturing technologies such as three-dimensional (3D) printing are facilitating the fabrication of personalised dosage forms with high precision in geometry and drug loading. In light of these advancements, the present thesis applies UV dissolution imaging to unveil the complex correlations between polymer properties, excipient selection and drug release mechanisms in matrix tablets. The effect of drug load is also investigated in 3D printed matrix tablets and their influence on the swelling, gel-layer formation and drug release rates. Initial studies focused on matrix compacts composed of polyethylene oxide (PEO), a synthetic polymer, or xanthan gum (XG), a natural polysaccharide, formulated with propranolol hydrochloride (PPN) as the model drug. Each polymer was blended with excipients of different solubility profiles (lactose, microcrystalline cellulose (MCC), and dibasic calcium phosphate (DCP)). The results showed that a higher ratio of lactose (1:3) in both PEO and XG formulations caused a faster drug release. The PEO:lactose 1:3 ratio achieved the highest dissolution efficiency (DE) (64 ± 8 %) and the shortest mean dissolution time (MDT) (77 ± 10 min) between the PEO formulations. The XG:lactose 1:3 ratio also exhibited the highest DE (61 ± 2 %) and the shortest mean dissolution time (MDT) (173 ± 7 min) among the XG formulations. Though the effect was less prominent compared to PEO formulations. The kinetic analysis displayed that most PEO formulations followed the Peppas model. The 𝑛 values suggested a non-Fickian transport driven by both diffusion and polymer erosion mechanisms. Most of the XG formulations followed the Higuchi model. Similarity factor (𝑓2) analysis showed the influence of excipient type and ratio on dissolution profiles. The PEO:MCC 3:1 and XG:MCC 3:1 formulations showed higher similarity to the pure polymer profiles. Focus variation microscopy and dissolution imaging were used to characterise tablet surface texture and to visualise swelling and dissolution fronts in real-time. For both PEO and XG polymers, an increase in the excipient content from a 3:1 to a 1:3 polymer-to-excipient ratio, generally improved initial wetting and accelerated drug release rate. In the case of PEO:lactose formulations, for example, the contact angle decreased from 44.6° at the 3:1 ratio to 29.6° at the 1:3 ratio. Whereas a higher polymer ratio formed a larger gel layer that slowed the drug release rate. For example, the XG:DCP 3:1 ratio achieved a swelling percentage of 207%, compared to 197% for the 1:1 ratio and 158% for the 1:3 ratio over the same period. A slower drug release is observed in in the higher polymer ratio, with the 3:1 XG:DCP releasing 20 µg/mL of the drug, while the 1:3 ratio released 26 µg/mL. The PEO:lactose 1:3 formulation had a faster hydration and PPN release, which can be attributed to its high porosity (21 ± 2%), low contact angle (29.6 ± 2.5°), and low Smr2 value (84.3 ± 0.4). Visual data recorded at 520 nm showed the development of a translucent gel layer in the matrix tablets after hydration. It also displayed the formation of deep channels in the gel layer of the polymer lactose compacts. A comparison of the two polymers showed that XG had a higher swelling percentage throughout all the formulations. The XG polymer had a higher ability for water uptake and gel layer formation reaching an average swelling percentage of 211%. PEO polymer, on the other hand, showed a lower swelling percentage of 135%. The choice and ratio of the excipient influenced surface properties, hydration rates and drug diffusion pathways. Overall, reducing the polymer content from a 3:1 to a 1:3 polymer to excipient ratio consistently increased drug release across both PEO and XG systems. For example, the 1:3 XG:DCP had a 30% higher release of the drug than the 3:1 XG:DCP ratio at the same time point. In the final stage, the research transitions from conventional compaction methods to the emerging field of fused deposition modelling (FDM) 3D printing. By incorporating PPN into PEO-based filaments plasticised with PEG 6K, the study shows how drug load can affect the mechanical properties, compact surface texture, wettability, swelling and dissolution profile. Higher drug amounts (40 mg) in the compacts resulted in greater gel development of 56% within the first 30 min of analysis. The gel layer behaved as a diffusion barrier and reduced the API release rate to 8% at 30 min. Lower drug content (10 mg), on the other hand, resulted in less swelling of 34% at 30 min and a faster drug release rate of 18 %. Dissolution imaging provided real-time visualisation of swelling fronts and channel formation in the 3D printed systems. Collectively, this body of work displayed the potential for regulating drug release by changing the quantity of the matrix gel former as well as the type or ratio of the excipient used. The study also highlights the novelty of using UV dissolution imaging to image and quantify swelling and drug dissolution processes. It also provides qualitative observations such as the formation of gel layer, dissolution fronts and channel formation which can support formulation optimisation and give a mechanistic understanding of the complex relationships between polymer composition, excipient selection and drug load in compressed and 3D printed oral drug delivery systems.