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Local irritation

Injections Absorbed quickly

Avoids GI tract Invasive

Pain

Complications such as infection

May be difficult to self-administer

Site specific, for example eye, ear, nasal, vaginal, rectal, pulmonary Often for local effects Discomfort and embarrassment

May be difficult to self-administer

Oral administration

Definition

Medication taken either through the mouth that is swallowed by the patient or administered via a feeding tube for example nasogastric, percutaneous endoscopic gastrostomy (PEG) (Snyder 2007).

Oral administration is the most convenient route for drug administration and may result in better compliance (Kelly and Wright 2009). It is the least expensive and is usually the safest. Due to their widespread use, oral drugs are prepared in a variety of dosage forms.

Related theory

Tablets

These come in a great variety of shapes, sizes, colours and types. The formulation may be very simple, presenting as a plain, white, uncoated tablet, or complex, designed with specific therapeutic aims. Sugar coatings are used to improve appearance and palatability. In cases where the drug is a gastric irritant or is broken down by gastric acid, an enteric coating may be used; this is designed to allow the tablet to remain intact in the stomach and to pass unchanged into the small bowel where the coating dissolves and the drug is released and absorbed. Tablets may be formulated specifically to achieve control of the rate of release of drug from the tablet as it passes through the alimentary tract. Terms such as ‘sustained-release’, ‘controlled-release’ and ‘modified-release’ are used by manufacturers to describe these preparations. Tablets may also be formulated specifically to dissolve readily (‘soluble’ or ‘effervescent’), to be chewed or to be held under the tongue (‘sublingual’) or placed between the gum and inside of the mouth (‘buccal’). Unscored or coated tablets should not be crushed or broken, nor should most ‘slow-release’ or ‘sustained-action’ tablets, since this can alter the rate of release of drug from the tablet (Smyth 2006).

Capsules

These offer a useful method of formulating drugs which are difficult to make into a tablet or are particularly unpalatable.

The capsule shells are usually made of gelatine and the contents of the capsules may be solid, liquid or of a paste-like consistency. The contents do not cause deterioration of the shell. The shell, however, is attacked by the digestive fluids and the contents are then released. Delayed-release capsule formulations also exist. Gastro-resistant capsules are delayed-release capsules that are intended to resist the gastric fluid and to release their active substance or substances in the intestinal fluid (British Pharmacopoeia 2007). If for any reason the capsule is unpalatable or the patient is unable to take it, the contents should not routinely be removed from the shell without first seeking advice from a pharmacist. Removing contents from the capsule could destroy their properties and cause gastric irritation or premature release of the drug into an incompatible pH (Downie et al. 2003).

Lozenges and pastilles

Lozenges and pastilles are solid, single-dose preparations intended to be sucked to obtain a local or systemic effect to the mouth and/or throat (British Pharmacopoeia 2007).

Linctuses, elixirs and mixtures

Linctuses

These are viscous oral liquids that may contain one or more active ingredients; the solution usually contains a high proportion of sucrose. Linctuses are intended for use in the treatment or relief of cough.

Elixirs

These are clear, flavoured oral liquids containing one or more active ingredients dissolved in a vehicle that usually contains a high proportion of sucrose. A vehicle is a substance usually without therapeutic action used as a medium to give bulk for the administration of medicines. If the active drug is sensitive to moisture it may be formulated as a flavoured powder or granulation and then dissolved in water just before use.

Mixtures

Mixtures are usually aqueous