Offering ease of use, the potential for increased patient compliance, and a way to extend the product life cycle of a drug,
orally disintegrating tablets (ODTs) continue to make inroads into the market for solid-dosage forms.
Patricia Van Arnum
Definition of ODT
Generally, an ODT is a solid-dosage form that disintegrates and dissolves in the mouth (either on or beneath the tongue or
in the buccal cavity) without water within 60 seconds or less (1). The US Food and Drug Administration's Center for Drug Evaluation
and Research developed the following definition for an ODT as a new dosage form in 1998: "A solid dosage form containing medicinal substances, which disintegrates rapidly, usually
within a matter of seconds, when placed upon the tongue" (2).
Earlier this year, FDA issued a draft guidance, Guidance for Industry: Orally Disintegrating Tablets (2), to recommend that, in addition to the original definition, ODTs be considered solid oral preparations that disintegrate rapidly in the oral cavity with an in vitro disintegration time of approximately 30 s or less, when based on the United States Pharmacopeia disintegration test method or alternative (see sidebar, "FDA issues ODT draft guidance").
The global ODT market (based on ex-factory sales to wholesalers) was estimated at $2.4 billion in 2004 and $3 billion in 2006,
according to Technology Catalysts International (3). Table I lists select examples of ODT drugs that are commercialized on
the US market.
Table I. Select examples of commercialized orally disintegrating tablets.
Recent market studies indicate that more than half of the patient population prefers ODTs to other dosage forms, and most
consumers would ask their doctors for ODTs (70%), purchase ODTs (70%), or prefer ODTs to regular tablets or liquids (greater
than 80%) (1).
Mechanism of ODT drugs
Generally, ODTs are formulated to disperse rapidly in the mouth, enabling medication to be swallowed without water, thereby
increasing convenience and compliance across a broad range of indications and patient types, including the young, elderly,
and active patients, explains Susan Banbury, project manager with Catalent Pharma Solutions (Swindon, UK). Following dispersion, the formulations are typically swallowed, and the drug is absorbed in the same way as
conventional solid-oral dosage forms.
"However, ODTs may also be used to deliver drugs to the oral cavity, for local action or, in some cases, absorption across
the oral mucosa, thereby avoiding first-pass hepatic metabolism and potentially increasing the rate and extent of uptake,
and reducing undesirable metabolites," says Banbury (4). The potential for such pregastric absorption rests largely in the
physicochemical characteristics of the drug molecule. The intrinsic taste of the drug is also a significant consideration
for all ODT formulations.
Types of ODTs
For ease of comparison, ODTs may be categorized into two main groups: lyophilized formulations and loosely compressed tablets.
Thin-film strips form a third category of solid, unit-dose, orally disintegrating products that aim to meet the same objectives
of ease of administration, patient convenience, and improved compliance.
FDA issues draft ODT guidance