Oral Dosing Training Document

Training Objective
This module describes the technique used to administer substances by the oral route using both gavage and tablet/capsule

Terminology

 
Gavage– Insertion of a cannula or tube into the stomach via the mouth and oesophagus.Catheter– A flexible tube for insertion into a narrow opening so fluids may be introducedCannula – Rigid tube for insertion into a narrow opening so fluids may be introduced (small
animals)

Prerequisites

 
  • Successfully completed Modules 1 – 3 Home Office training course
  • Project licence authorities & personal licence in place
  • Have read and understand licence limits & protocol
  • Able to competently handle and restrain animal for the procedure
  • Able to identify & use correct size of dosing equipment to complete procedure
  • Able to calculate dose volumes & correctly fill syringe
  • Awareness of EHS and if applicable read and understood sop documentation

 

Competence Criteria
  • Demonstrate the ability to perform technique
  • Understand what action to take if problems occur
  • Answer questions relating to the procedure

 

Principles
Oral administration using a catheter / cannula tube gives an accurate dose via the oesophagus into the stomach for experimental reasonsTablets and capsules may have a slower release.Compounds, which are given orally, may be absorbed at various points in the gastrointestinal tract. The rate of absorption will be slower orally than if the drug was administered via the intra venous route.

Procedure

Catheter/Cannula Dosing
  • Attach catheter/cannula to syringe (some catheters require cutting to ensure tight fit onto syringe).
  • Substance should be at room temperature & thoroughly mixed.
  • Draw substance to be administered up into syringe through the catheter/cannula ensuring all air/excess substance is removed.
  • Wipe outside surface of catheter.
  • If using a catheter/cannula it is good practice to mark the length required to access the stomach. This is done by measuring the catheter/cannula against the ventral surface of the animal from the mouth to the stomach (located just below the rib cage) See fig. 2.
  • Remove animal from the cage / pen if applicable.
  • Check identification/label to ensure correct animal.
  • Fig 1 shows examples of catheter types

Fig 1

 
  • Restrain the animal as appropriate to the species ensuring head is immobilised to allow the insertion of the cannula or catheter into the mouth.
  • Smoothly feed the catheter or cannula down the side of incisors into the back of the mouth past the larynx and down the oesophagus into the stomach. (if using a catheter feed down to the mark made on it, cannula are usually fully inserted, although length should be checked as with the catheter).
  • When dosing dogs it may be appropriate to “flush” the dose in with 10mls of water.
  • Administer substance at a steady rate.
  • Withdraw the catheter or cannula in a smooth steady action.
  • Release the animal and return it to its home cage / pen
  • Check the animal at an appropriate time (this may be protocol driven) to ensure no reaction to procedure or substance administered.

 

Fig 2


Example of measuring cannula length for rat oral dosing

Example of Dog dosing showing correct position of catheter

 

 

Tablet/capsule – Large animals
Dog –

 

  • If appropriate remove animal from pen. This procedure is often completed within the dog pen
  • Check identification/label to ensure correct animal.
  • Restrain the animal as appropriate ensuring neck is tilted upwards & ensuring head is immobilised to allow the mouth to be opened by applying pressure to upper jaw, use fingers on other hand to gently open lower jaw. Place tablet/capsule onto the back of the tongue, close the mouth and massage throat area.  View after dosing to ensure not regurgitated or held in the mouth and spat out. If in doubt open mouth to ensure swallowed. Often dogs will lick their lips once the tablet has been swallowed.
  • Release the animal and return it to its home cage / pen.
  • Check the animal at an appropriate time (this may be protocol driven) to ensure no reaction to procedure or substance administered.

 

 

Possible Problems

 

Animal
may move or flinch

 Ensure restraint adequate for procedure.

Animal may bite catheter or cannula –

Replace catheter or cannula, try to keep apparatus to side of teeth to stop animal biting it.

Ensure  restraint adequate to prevent animal moving its head and allowing access to the catheter or cannula by the teeth

Animal may bite off cannula / catheter

 Keep animal scruffed and try to retrieve
bitten off end with forceps. If cannot be retrieved seek veterinary advice or
consider euthanasia

Resistance when advancing catheter/cannula

 DO NOT continue to advance – may be in
trachea. Withdraw the catheter / cannula immediately
The animal may be closing the cardiac sphincter muscle at the entrance to the stomach. DO NOT dose as animal will reflux. Withdraw the catheter / cannula immediately

Resistance when advancing catheter/cannula (continued)

 The animal may have eaten and there is food in the oesophagus (evidence of food on catheter tip)

Coughing at dosing

Coughing may indicate that the catheter is in the trachea, withdraw immediately

Blood visible in/on catheter

Possible rupture of oesophagus or fed down the trachea into or through the lung – seek advice
Reflux of substance/food through nose/mouth

Possible damage to catheter/cannula check and replace

Substance administered too quickly

Administration of substance into the oesophagus or against a closed cardiac sphincter. It is unwise to re-administer substance if reflux occurs as there is no accurate way to assess how much of the substance was lost or administered during original attempt- document and inform relevant people
Animal may have just eaten and stomach full of food
Mis-dosed In small animals if dose goes into the lungs death may occur quickly

A partial dose to the lungs clinical signs may be noted several hours/days later Increase observations if signs are noted. Clinical condition of the animal may deteriorate over time, dependant on problem, e.g. discharge of red/brown substance from the nose and or eyes, respiratory problems, pallor, lethargy.
Tablet/capsule not swallowed – close mouth
and continue to massage neck

Capsule bitten – document

Capsule/tablet spat out – document, if intact re-dose

Adverse reaction

 Adverse reaction to substance administered – (e.g. excess salivation) – document in study records, if severe or exceeding project licence expectations, refer to project licence for actions, contact a senior animal technician, the NVS or the NACWO or consider euthanasia.



 

Any problems experienced will need to be recorded on either appropriate study paperwork or lab book. It should also be reported to either a senior animal technician, NVS, NACWO or Project licence holder if circumstances deteriorate euthanasia should be considered

 

 

 

Records
Complete dosing records and experimental observations.

Safety

 

Risk

Precaution
Spray from dose Ensure catheter/cannula is firmly attached to syringeWear appropriate PPE
Bite & scratch Wear appropriate PPEEnsure handling techniques are correct