Selection of Drug Candidates

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Selection of drug candidates for controlled release dosage forms. Learn drug candidates are unsuitable for controlled release drug delivery.

Selection of Drug Candidates

Drugs that undergo hepatic first-pass metabolism should not be formulated in a controlled release dosage form because it would reduce their absorption rate. On the other hand, there is limited medical justification for formulating drugs with a long biological half-life (i.e., > 12 hours) in a controlled release formulation, since these drugs are already long acting, unless the controlled release formulation offers convenience to the patient and improves patient compliance.

What are the ideal properties of a drug suitable for a sustained release drug delivery system (SRDDS)?

  1. It absorbed upon oral administration and remained stable in gastrointestinal fluid.
  2. It should have a short half-life (2-4 hours), for example, captopril, salbutamol sulphate, etc.
  3. Drug should not be less than 0.5gm, and the maximum dose for designing SRDDS should be 1.0gm, e.g., metronidazole.
  4. It should have a wide therapeutic range so that any variation in drug release does not lead to concentrations beyond the minimum toxic levels.

Who are unsuitable for controlled release drug delivery systems (CRDDS)?

  1. Drugs with an elimination half-life < 2 hours or drugs requiring large doses for administration within the body.
  2. Drugs with a half-life > 8 hours are not suitable for formulation as controlled release dosage forms.
  3. Drugs with low solubility and those requiring administration in a large number of doses are also inappropriate for designing CRDDS.

In summary, drugs with short or long half-lives, those undergoing hepatic first-pass metabolism, drugs with low solubility, and drugs requiring frequent administration are considered unsuitable for controlled release dosage forms. Careful consideration of these factors is crucial in selecting appropriate drug candidates for controlled and sustained release formulations.

You may also read Controlled drug delivery systems in NDDS.

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