Oesophageal Transit Of Dosage Forms Measurement

Oesophageal transit is usually assessed clinically by x-ray study of a swallowed bolus of barium sulphate suspension. Very early studies also used barium to assess oesophageal transit of variety of substances such as gelatin cylinders2, marshmallows3 4, cotton pledgets, tablets5 6 and capsules7. However, later studies demonstrated that dense materials such as barium have faster transit than more physiological substances. In addition, X-ray contrast techniques are difficult to quantify and are associated with a significant radiation burden on the subjects. Consequently, gamma scintigraphy has become the method of choice to assess oesophageal transit. It has the advantages that any suitably labelled test material, food or dosage forms can be followed and radiation dosimetry is very small allowing repeat studies in individuals. It is a quantifiable technique since transit can be expressed as position of radioactivity against time (Figure 4.4).

Figure 4.4 Plot of position of activity versus time for a swallow of technetium-99m-

DTPA labelled water

Figure 4.4 Plot of position of activity versus time for a swallow of technetium-99m-

DTPA labelled water

Table 4.1 Typical transit times for various pharmaceutical dosage forms **ODT—Orally dissolving tablet

Formulation Weight & dimensions Transit time Posture

Seconds

Tablet Round

1 OOmg 6mm diameter

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