Chewable tablets, bioavailability

Drug absorption is highly variable in neonates and infants [21,22]. Older children appear to have absorption patterns similar to adults unless chronic illness or surgical procedures alter absorption. Differences in bile excretion, bowel length, and surface area probably contribute to the reduced bioavailability of cyclosporine seen in pediatric liver transplant patients [22a]. Impaired absorption has also been observed in severely malnourished children [22b]. A rapid GI transit time may contribute to the malabsorption of carbamazepine tablets, which has been reported in a child [23]. Selection of a more readily available bioavailable dosage form, such as chewable tablets or liquids, should be promoted for pediatric patients. 

Chewable tablets and sprinkle capsule formulations have been very well received by both patients and their parents for use in children with full dentition (older than 3 years, [75-77]. This is potentially a very fruitful area for future research and development. Pharmaceutical preparations developed for administration to young children need to have consistent bioavailability when administered with food [78]. 

S. Abdel-Rahman, D. Blowey, R. Kauffmann, and G. Kearns, Comparative bioavailability of loracarbef chewable tablet vs. oral suspension in children, Pediatr. Infect. Dis. J., 17(12), 1171 (1998). 

Sales of Ca supplements alone were 875 million in the United States in 2002, and comprised 60% of all mineral supplement sales (Anonymous, 2004). In 2004, sales of Ca supplements increased by 9.3% (Uhland et ah, 2004), possibly to some extent in response to the Surgeon General s report on bone health that was issued that year. More recently in 2006, it was projected that dietary supplement sales in the United States would approach 5 billion (Anonymous, 2006). While Ca derived from a balanced diet is preferable, Ca supplements are a popular noncaloric alternative for increasing daily Ca intake. There are a vast number of oral Ca supplements available in the market place in the form of capsules, tablets, chewable tablets, effervescent tablets, liquids, powders, suspensions, wafers, and granules. However, not all Ca salts are equally soluble or bioavailable and the dose of Ca on the label of a supplement may not necessarily be reflective of the relative amount of available Ca once consumed. Furthermore, the same Ca salt may be more or less bioavailable depending on the production process and materials used to manufacture the supplement. 

The oral bioavailability of didanosine is about 35 15%. Food may decrease its absorption by 50% or more. As a consequence, it should be administered a minimum of 30 min before or 2 h after eating. Peak plasma concentrations are reached within 1 or 2 h of administration after a chewable tablet and delayed release capsule,... 

The original formulation, a buffered powder, has been replaced by chewable and dispersible buffered tablets with greater bioavailability (30-40%) a new enteric-coated formulation further improves patient convenience and tolerability. Since the chewable tablets contain both phenylalanine (36.5 mg) and sodium (1380 mg), caution should be exercised in patients with phenylketonuria and those taking sodium-restricted diets. Didanosine should be taken on an empty stomach and, because of the buffered formulation, should be administered at least 2 hours after administration of drugs requiring acidity for optimal absorption (eg, ketoconazole, itraconazole, dapsone). 

Chewable tablets are designed to be mechanically disintegrated in the mouth. Potential advantages of chewable tablets are mainly concerning patient convenience and acceptance, although enhanced bioavailability is also claimed. This can be due... 

Didanosine chewable tablets contain antacids (aluminium/magnesium hydroxide) in the formulation, but it has been shown that they do not affect the bioavailability of isoniazid. ... 

Knupp CA, Milbrath R, Barbhaiya RH. Effect of time of food administration on the bioavailability of didanosine from a chewable tablet formulation. J Clin Pharmacol (1993) 33, 568-73. 

Absorption/Distribution - Lamotrigine is rapidly and completely absorbed after oral administration. Absolute bioavailability is 98%. Peak plasma concentrations occur anywhere from 1.4 to 4.8 hours following drug administration. Lamotrigine chewable/dispersible tablets were found to be equivalent, whether they were administered as dispersed in water, chewed and swallowed, or swallowed as whole, to lamotrigine compressed tablets in terms of rate and extent of absorption. 

---