38 A powder may be defined as a solid material in a finely divided state. Granules are powders agglomerated to produce larger free-flowing particles. Powders and granules can be used to prepare other formulations, such as solutions, suspensions and tablets. A powdered drug on its own can be a dosage form for taking orally (called a simple powder), when they are usually mixed with water first, or for external application as a dusting powder. Alternatively, the drug may be blended with other ingredients (called a compound powder). Individually wrapped powders tend not to be official formulae and are rarely prescribed these days (see Examples 38.1 and 38.2). Magnesium Trisilicate Powder Compound BP (see Example 38.4) and Compound Kaolin Powder BP are examples of bulk powders for internal use. Proprietary powders and granules include Dioralyte®, Electrolade® (both oral rehydration salts), Normacol® (sterculia) and Fybogel® (ispaghula husk). Supplying as an undivided powder is useful for non-potent, bulky drugs with a large dose, e.g. antacids, or when the dry powder is more stable than its liquid-containing counterpart. A bulk powder can be supplied to the patient although this is rarely seen nowadays because the dosage form is inconvenient to carry and there are possible inaccuracies in measuring the dose. Individually wrapped powders are used to supply some potent drugs, where accuracy of dose is important. Extemporaneously produced powders are wrapped separately in paper. They are convenient dosage forms for children’s doses of drugs which are not commercially available at the strength required, such as levothyroxine (thyroxine) or ibuprofen (see Example 38.2). Sealed sachets of powders are available commercially, e.g. Paramax® (paracetamol and metoclopramide) and oral rehydration salts. They are mixed with water prior to taking and are useful for patients who have difficulty swallowing or where rapid absorption of the drug is required.
Powders and granules
Introduction
Powders for internal use
Bulk powders
Individually wrapped powders
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