Dosage forms

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Editor, – Professor Ravenscroft, in his article 'Opioids - clinical applications in palliative care' (Aust Prescr 1996;19:66-8), and Dr Lloyd and Professor Bochner, in their article' Aspirin: how low is low dose?' (Aust Prescr 1996;19:79-81), have provided excellent summaries of the use of these drugs in their respective applications.

The opioid article, however, omitted to mention an additional sustained-release morphine dosage form which happens to be a capsule. The two sustained-release dosage forms do not have super imposable pharmacokinetic profiles.
The aspirin article correctly states that there are 3 alternative low-dose aspirin dosage forms in Australia, but suggests that they are tablets. One of the dosage forms contains enteric-coated, extended-release pellets in hardgelatine capsules.
Some health care providers may consider distinguishing capsules from tablets to be trivial. Some patients, however, find swallowing one dosage form easier than others. Pharmaceutical factors can alter drug tolerance and release profiles.
Enteric-coated dosage forms can reduce gastric irritation or protect drugs from acid degradation. Dosage forms which consist of multiple units compared with tablet formulations can minimise localised concentrations of drugs in the gut lumen, leading to reduced irritation. For sustained-release products, with other factors being equivalent, the dosage form which provides the smallest peak to trough variation between doses should be prescribed.

For some drugs, it is important to mention these issues when reviewing their clinical applications. Any means for improving patient acceptance or compliance should be carefully considered when prescribing drugs for the first time, or when reviewing progress on repeat prescriptions. Clinicians will be better informed and pharmacists will be better able to provide effective patient counseling at the time of dispensing.

Desmond B. Williams
Pharmaceutical Technology Consultant
Adjunct Lecturer, School of Pharmacy and Medical Sciences
University of South Australia