Oral administration

This is the most frequently used route of drug administration and is the most convenient and economic. Solid dose forms such as tablets and capsules have a high degree of drug stability and provide accurate dosage. Medications administered orally pass down the digestive tract for absorption usually from the small intestine to the liver via the portal vein. Once the medicine has been metabolised by enzymes in the liver, it enters the circulation for systemic effect. It is important to understand the pharmacology of the indiviual medication.

The oral route is nevertheless problematic because of the unpredictable nature of gastro-intestinal drug absorption. For example the presence of food in the gastrointestinal tract may alter the gut pH, gastric motility and emptying time, as well as the rate and extent of drug absorption.

The extent to which patients can tolerate solid dose forms also varies, particularly in very young and older patients. In such cases the use of liquids or soluble formulations may be helpful. Many drugs, however, are not stable in solution for liquid formulation and in such cases careful consideration should be given to the option of switching to alternative drug treatment.

Difficulties frequently arise with patients who are prescribed modified-release preparations as these must not be crushed or broken at the point of administration. Modified-release formulations can delay, prolong or target drug delivery. The aim is to maintain plasma drug concentrations for extended periods above the minimum effective concentration.

For patients, their main advantage is that doses usually only need to be taken once or twice daily. Damage to the release controlling mechanism, for example by chewing or crushing, can result in the full dose of drug being released at once rather than over a number of hours. This may then be absorbed leading to toxicity or may not be absorbed at all leading to sub optimal treatment.

Nurses should seek advice from a pharmacist or the prescribing doctor if they are uncertain about a formulation of solid dose forms and whether or not they are suitable for crushing.

Some oral drugs can have a local effect e.g. oral antacids reduce the stomach acidity.

The oral route is the most common route of administration. This is for several reasons:

· It is associated with less pain and anxiety than other routes such as intramuscular injections

· It is often cheaper than other preparations such as intravenous

· Less equipment is required and the procedure is often less time-consuming and more convenient.

CONTRAINDICATIONS:

· Unconscious state

· Absent gag reflex

· Inability to swallow

· Vomiting

CAUTIONS:

· Digestive tract trauma/illness

· Post gastro-intestinal surgery

· Nil-by-mouth

· Nausea

· Diarrhoea

Sublingual

The sublingual mucosa offers a rich supply of blood vessels through which drugs can be absorbed. This is not a common route of administration but it offers rapid absorption into the systemic circulation. The most common example of sublingual administration is glyceryl trinitrate in the treatment of acute angina.

The pharmaceutical industry has formulated and marketed ‘wafer’-based versions of tablets that dissolve rapidly under the tongue. These are aimed at particular markets where taking tablets may be problematic, such as the treatment of migraine (rizatriptan) where symptoms of nausea may deter patients from taking oral treatments. The formulation is also used to treat conditions where compliance with prescribed drug regimens may be problematic, for example, olanzapine used to treat schizophrenia can be administered by the sublingual route.

Date: 2014-12-29; view: 1029