Conventional tablets are difficult to be swallowed by paediatrics, geriatrics or patients suffering from dysphagia which can sometimes make it difficult to elicit the desired therapeutic effect. Pharmaceutical mini tablet, a modern variant of the conventional compressed tablet can help effectively overcome this challenge. It is usually smaller than or equal to 4 mm in diameter. Besides ease of swallowability, some of the other important advantages of mini tablets include reduced risk of dose dumping, excellent size uniformity, high degree of dispersion in the digestive tract, ease of manufacturing, ease of coating for modified release and ease of transportation.  

Manufacturing minitablets involves a similar manufacturing setup that is used for conventional tablets and comprises of multi–punch eccentric or rotary tablet press machines. As it requires the use of small dies, excellent powder flow property is key to ensure uniform filling. With respect to mechanical resistance, minitablets are more robust and display lower capping tendency in comparison with conventional tablets due to their high surface area per volume ratio. This results in increased area of contact between powder mixture and punch/die wall, leading to homogeneous distribution of punch pressure for effective bonding of particles. Minitablets can be further compressed in a tablet or filled in capsules, sachets etc. 

Mini tablets can be classified on basis of their applications: 

Gastro-retentive minitablets – Gastro-retentive mini tablets ensures release of drug in stomach for prolonged time period.  

Orally disintegrating minitablets – Orally disintegrating mini tablets disintegrate in the mouth within seconds of coming in contact with the saliva.  

Bioadhesive vaginal minitablets – These tablets are formulated with bio adhesive polymers or hydrophilic polymers which help in better adherence to vaginal mucosal surface. 

Ocular minitablets – Ocular minitablets are bioadhesive mini tablets ranging from 2-4 mm in diameter which can be placed in the eyes.  

Biphasic minitablets – Biphasic mini tablets have two layers- an immediate release layer and a sustained release layer. These minitablets are used when an initial loading dose of drug has to be delivered followed by a maintenance dose.  

Ocular Minitablets 

The most commonly used ocular delivery systems are ocular solutions and suspensions. However, they need frequent administration, as only a small quantity of it is retained in the eye and may sometimes also cause blurred vision. Minitablets as a novel dosage form for ocular application can greatly help overcome the drawbacks of conventional ocular delivery systems.  

Once the minitablets are placed in the eye, the drug is slowly eroded from its surface over a period of time. Another mechanism of drug release from minitablets is by their in-situ conversion into a gel mesh matrix on administration. Ocular minitablets are an advanced form of drug delivery since the release of drug can be controlled in a preset manner.  

Better bioavailability, extended duration of action, reduced number of doses, minimised systemic side effects, accurate dosing, increased shelf life as compared  to aqueous solutions,   reduced risk of flushing out due to lacrimation and drainage on administration, are some of the advantages of ocular minitablets.  These solid dosage forms also allow for increased corneal contact time owing to the use of bioadhesive polymers.  

Minitablets provide targeted drug delivery especially useful for infections of cul-de-sac, anterior segment targeting, microbial keratitis etc. Gentamicin, timolol and ciprofloxacin are some drugs that have been formulated as ocular minitablets.  

Although solutions, suspensions or ointments are the most commonly used ocular drug delivery systems and standard for treatment of conditions of the anterior eye, minitablets are promising alternatives, with greater patient compliance, better targeting, and consequently higher bioavailability. Minitablets allow for a high degree of formulation flexibility during and have the potential to be used effectively for a variety of diseases. 

References 

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