Dr Merchant has a particular interest in drug delivery research at the interface of gastroenterology and publishes in various aspects of oral delivery. For collaboration and technical support in following areas, please feel free to contact him.

CoViD-19: the novel coronavirus disease

Dr Merchant has proposed an early intervention therapeutic strategy for CoViD-19 to prevent developing a severe disease as an alternative approach to control the pandemic. He believes that the global burden of CoViD-19 on the healthcare system can be significantly reduced by targeting CoViD-19 patients with or without symptoms who are self-isolating at home or in a quarantine. If a therapeutic support can be offered to this group of patients that could attenuate the virus within the upper respiratory tract during the early stages of CoViD-19, it can give the body the time to produce enough antibodies to recover naturally from the disease before progressing into severe disease. An early intervention can, therefore, prevent the virus to get down the lower respiratory tract, reduce the number of cases with severe disease involving pneumonia and the need for hospitalisation. The concept has been published as a preprint in detail and a treatment summary has been published as a letter to the editor in the BMJ. 

Dr Merchant has also been the part of the evidence synthesis group at Huddersfield for better use of medicines during CoViD-19 and have contributed significnalty by publishing in peer-reviewed journals, contirbuting to the media, and range of public education campaigns, both in English and Urdu languages. A few examples of his CoViD-19 contributions inclue: predicting the mortality benefits of steroids early in the pandemic, the benefits of using inhalable corticosteroids in asthma and COPD patients amid pandemic, a critical review of alcohol based hand sanitisers on the market and formulation approaches to respond to the increasing demand, an early warning in the pandemic against antimalarials as cures for coronavirus, and the review of CoViD-19 cases, associated hospitalisation, and mortality.  

Formulation development

The advancements in materials sciences and improved understanding of the human gastrointestinal (GI) environment are leading to intelligent design of formulations. The rationale design and selection of delivery technologies improves the performance of orally administered drugs, for example, by improving drug solubility, flux or by delivering it to the specific gastrointestinal regions. Our research in formulation sciences offers novel and customised solutions for immediate and delayed release formulations; and drug targeting in GI tract, such as delivery to the colon.

Dissolution and permeation of drugs

Drug dissolution in gastrointestinal fluid and its permeation through the gastrointestinal mucosa is a key consideration for its absorption. Our research continues to explore and develop various in-vitro technologies to provide a reasonable estimation of absorption and help selecting a lead formulation for clinical evaluation. .

One of our innovative strategies is the exploitation of physiological bicarbonate buffers for dissolution testing. This led to the development of an Auto pH System™ – a robust instrumentation and dynamic dissolution media employing physiological bicarbonate buffers simulating the aboral changes in gastrointestinal pH while dosage form transits down the gut after emptying from stomach (PCT/GB2013/051145). The system exploits the physiological equilibrium of bicarbonate/carbonic acids to control and manipulate the pH and offers a robust automatic pH control without using conventional non-physiological acid/base titration techniques. .

The novel system has numerous applications in drug delivery and has been employed to assess dissolution and drug release from various delivery systems, such as: .

• Dissolution screening of drugs and its salt forms

  Example: Dissolution in pH 5.6 bicarbonate buffer stabilized using a novel control system to discriminate between ibuprofen and its salt forms, AAPS 2013-R6065.

• Evaluation of gastro-resistant formulations

  Example: The assessment of enteric-coated formulations under dynamic dissolution conditions simulating the pH conditions of the proximal gut, AAPS 2013-T3050.

• Inter-individual variability of GI pH and transit and consequences on drug release

  Example: Drug release from pH responsive ileo-colonic systems: Simulation of inter-individual variability using a novel dynamic dissolution system mimicking the entire spectrum of gastrointestinal pH, AAPS 2013-W5338.

• Evaluation of delayed-release formulations for colonic targeting

  Example: Dynamic dissolution of modified release mesalamine products using bicarbonate buffers, AAPS 2013-T3119.

• Evaluation of sustained-/controlled-release formulations

  Example: Use of physiological bicarbonate buffers provides more realistic behaviour of sustained release formulations compared to compendial phosphate buffers, AAPS 2013-R6310.

Preclinical models in drug delivery

Pre-clinical testing is paramount for the improved understanding of the behaviour of orally administered drugs. Various animal models are used with the aim to mimic as closely as possible the conditions of the human gastrointestinal tract. The characteristics of the gastrointestinal milieu have a significant influence on orally administered drugs. Therefore, rational selection of animal models for a specific delivery technology is a key to successful translation of preclinical observations to clinic. We have investigated the gastrointestinal milieu of various animal models, such as mice, rat, guinea pig, rabbit and pig, and their effects on drug solubility and absorption. We have also explored the effects of ageing in gastrointestinal environment of rat in relation to drug delivery.

For a complete list of peer-reviewed publications, please refer the Publications section.