Spacer Health Dictionary

  1. Health Encyclopedia
  2. Spacer

Spacer: From 1 Different Sources

n. a plastic container with a mouthpiece at one end and a hole for an aerosol inhaler at the other. The dose from the inhaler is sprayed into the spacer, from which it can be inhaled without needing to coordinate breathing. It is particularly useful for babies and small children who do not have this coordination. Paediatric spacers also have a small mask that fits onto the mouthpiece of the spacer and is placed over the child’s nose and mouth. Spacers help to deliver a greater proportion of the dose to the airways while reducing the proportion absorbed into the body (which is the usual cause of unwanted side-effects)
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Beta-adrenoceptor-blocking Drugs

Also called beta blockers, these drugs interrupt the transmission of neuronal messages via the body’s adrenergic receptor sites. In the HEART these are called beta1 (cardioselective) receptors. Another type – beta2 (non-cardioselective) receptors – is sited in the airways, blood vessels, and organs such as the eye, liver and pancreas. Cardioselective beta blockers act primarily on beta1 receptors, whereas non-cardioselective drugs act on both varieties, beta1 and beta2. (The neurotransmissions interrupted at the beta-receptor sites through the body by the beta blockers are initiated in the ADRENAL GLANDS: this is why these drugs are sometimes described as beta-adrenergic-blocking agents.)

They work by blocking the stimulation of beta adrenergic receptors by the neurotransmitters adrenaline and noradrenaline, which are produced at the nerve endings of that part of the SYMPATHETIC NERVOUS SYSTEM – the autonomous (involuntary) network

– which facilitates the body’s reaction to anxiety, stress and exercise – the ‘fear and ?ight’ response.

Beta1 blockers reduce the frequency and force of the heartbeat; beta2 blockers prevent vasodilation (increase in the diameter of blood vessels), thus in?uencing the patient’s blood pressure. Beta1 blockers also affect blood pressure, but the mechanism of their action is unclear. They can reduce to normal an abnormally fast heart rate so the power of the heart can be concomitantly controlled: this reduces the oxygen requirements of the heart with an advantageous knock-on e?ect on the respiratory system. These are valuable therapeutic effects in patients with ANGINA or who have had a myocardial infarction (heart attack – see HEART, DISEASES OF), or who suffer from HYPERTENSION. Beta2 blockers reduce tremors in muscles elsewhere in the body which are a feature of anxiety or the result of thyrotoxicosis (an overactive thyroid gland – see under THYROID GLAND, DISEASES OF). Noncardioselective blockers also reduce the abnormal pressure caused by the increase in the ?uid in the eyeball that characterises GLAUCOMA.

Many beta-blocking drugs are now available; minor therapeutic di?erences between them may in?uence the choice of a drug for a particular patient. Among the common drugs are:

Primarily cardioselective Non-cardioselective
Acebutolol Labetalol
Atenolol Nadolol
Betaxolol Oxprenolol
Celiprolol Propanolol
Metoprolol Timolol

These powerful drugs have various side-effects and should be prescribed and monitored with care. In particular, people who suffer from asthma, bronchitis or other respiratory problems may develop breathing diffculties. Long-term treatment with beta blockers should not be suddenly stopped, as this may precipitate a severe recurrence of the patient’s symptoms – including, possibly, a sharp rise in blood pressure. Gradual withdrawal of medication should mitigate untoward effects.... beta-adrenoceptor-blocking drugs


Health encyclopedia icon Health Encyclopedia

Recent Searches