(15/10/2005) Absorption

Absorption

Most medicines for internal use, however they are administered (by mouth, injection, spraying), have to be absorbed from the point at which this occurs, i.e. have to travel further in order to reach the appropriate organ or organs. There are clear differences in the way the various active ingredients are absorbed, and to ignore these can cause treatment to be unsuccessful.

Absorption from the intestinal system

Most often, we treat the flock by mouth. Different drugs behave differently in the intestinal canal, or are absorbed from it in different ways.

Of the various vitamins, vitamins soluble in fat (vitamins A, D, E and K) can only be absorbed from the intestinal canal if there is enough grease in the food consumed simultaneously with them. The seeds of cereals contain vegetable oil in adequate quantities, and so we only have to see that pigeons have enough feed during the course of vitamins. If for some reason this does not happen – e.g. due to illness – we should be aware that a fat-soluble vitamin provided in drinking water, though drunk by the pigeons, will not be absorbed adequately and thus will not be effective. When a pigeon has not eaten for days, it is preferable to provide fat-soluble vitamins in injected form.

Antibiotics given by mouth are absorbed from the alimentary canal in varying quantities. The absorption of certain agents is affected by how full the intestinal canal is, e.g. ampicillin, while for others, like amoxicillin, it is not.
We list those antibiotics administered by mouth but which are not absorbed from the gut. We do this because even professionals can commit the error, for example, of trying to treat respiratory illness with antibiotics administered by mouth but not getting any further than the intestines. If given by mouth, we can only expect such drugs to have an effect in the intestinal canal itself; if the pathogens also attack other organs (respiratory passages, joints, etc.), the drug will not reach them.
The following antibiotics are hardly absorbed from the intestinal canal, if at all: neomycin, streptomycin, colistin, gentamycin, spectinomycin.
The fact that certain antibiotics are not absorbed from the intestines can be advantageous. If we only want to treat enteritis, it is advisable to choose from among agents that are not absorbed, for by staying in the intestinal tract these put the lightest burden on the bird’s system.

The absorption of the active ingredients from the intestinal canal affected by many factors. The pH value of the intestinal contents is not insignificant, e.g. in the case of tetracyclines, especially doxycycline. If we get the flock to drink doxycycline, we should always introduce organic acid to the medicated drinking water – the easiest being apple vinegar or a ready-made acid mixture. Doxycycline is much more readily absorbed from an acidic environment than from an alkaline one.
In the case of intestinal inflammation, the penetrability of the intestinal wall is altered, which can equally cause increased or decreased absorption. If the intestinal inflammation is accompanied by diarrhoea, the increased rate of excretion of faeces means that the intestinal contents leave the system faster than expected, resulting in decreased absorption of the medicine. For this reason, if the diarrhoea is severe, it may be necessary to complement the treatment with injections.

Absorption of injected drugs

Unless we commit some vaccination error, the agent in an injection given below the skin or in a muscle is generally absorbed quickly. An expertly performed injection is more certain to be effective than a product given by mouth. It has the following drawbacks, however:

• risks associated with injections (damage to certain muscle groups; embolism)
• laborious and time-consuming if applied to the whole flock
• disturbs the specimen and the flock
• the needle can transfer infection (if not changed)

Despite these disadvantages, in many cases, e.g. when using immunizing vaccines, we have no choice but to use an injection. It is a common complaint that after vaccination the location of the injection become “knotted”, a change which does not disappear of its own accord. This is particularly observable in the case of oil-based vaccines, if the substance is not administered deep enough (if it was injected into the skin, not the tissue underneath it). Another cause can be the use of a vaccine that is too cold, or failing gently to massage the point of injection. If we identify such a protrusion a few days after the injection, we can usually eliminate it with the local application of creams causing hyperaemia (camphoric or mentholated substances), and it is absorbed without trace.

Transdermal absorption

Many agents are absorbed through the skin if applied to it externally. There are products (e.g. certain substances against parasites) that must be dripped onto the skin. The active ingredient spreads over the surface of the skin and/or is absorbed through it, and once in the bloodstream exerts its effect throughout the body.
Transdermal absorption has its dangers, however. Some products attacking parasites cannot be used on pigeons, because if absorbed through the skin, the active agent causes poisoning, or even death. These substances can be absorbed through a person’s skin in the same way, and so we should always use protective materials (rubber gloves, face mask), if, for example, we are spraying an empty cage with such products!

Dr. Zsolt Talabér (edited by Martin Degrave) - 15/10/2005