Using numbers and handling data
Using numbers and handling data

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Using numbers and handling data

2.5 What is a sensible dose?

This will vary from drug to drug and patient to patient, but bear in mind that most drugs need to be swallowed or injected, so the manufacturer has designed the dose sizes to be as easy as possible for a patient to take and for the health worker to administer.

The following dose ranges are the most sensible and practical for adults:

Table 7 Typical drug doses

Drug formulationTypical dose at any one time
Liquidoral: 5-20 ml (1-4 teaspoons full)
injection: generally 0.25-2 ml
subcutaneous: 1 ml or less
intramuscular: adults - up to 3 ml in large muscles
children and elderly - up to 2 ml
infants - 1 ml or less
Solid1-4 tablets
Gas0.2-150 litres/min
Radiation dose20-70 μSv for an X-ray, 100-200 Sv for radiotherapy
For each category, the doses for a baby or a child are normally much less than adult doses.

If you find that the dose you have calculated or the prescription you have been given is outside of this range, especially if it is out by a factor of 10, 100 etc., then it's likely that a mistake has happened somewhere. If it's your own calculation, then double-check it. If it still doesn't look right, or was written that way on the prescription then check with a senior colleague.

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