Examples of different formulations: oral suspension, rapid release, delayed release
Variables:
(1) bioavailability and absorption
(2) rate of drug release
If a new formulation has better absorption/bioavailability than a current one, then the same dose of the new formulation will result in high drug levels, possibly causing toxicity.
If a new formulation has a lowe absorption then the same dose could cause a subtherapeutic dose.
If a drug has a slower release than another, then the drug concentration will probably be more constant.
If a drug has a faster release, then there may be wider swings in drug concentration. Use of a smaller dose more often may be necessary.
If one formulation has similar bioavailability and a rate of drug release to another, then the same dose can be used. Else problems may occur.
