Drug Doses And Administration

Question 1

LO: Calculate a quantity of drug to be administered via the
> enteral (oral) route
> parenteral route

Answer 1

Information required:

1. Weight of the patient in kilograms (kg)
2. Dose rate usually in milligrams per kilogram (mg/kg)
3. Drug concentration usually in milligrams per tablet (mg/tablet)

Take care with units! Miscalculation can lead to under/overdosing patient

Enteral Medication:

No of tablets = [weight of animal (kg) x dose rate (mg/kg)] / drug conc (mg/tablet)

Parenteral Medication:

Vol of drug (ml) = [weight of animal (kg) x dose rate (mg/kg)] / drug conc (mg/ml)

Question 2

LO: Identify factors which must be considered when administering parenteral medication

Answer 2

Solution V Suspension

Solution = soluble substance dissolved in a solvent e.g. water
Suspension = insoluble substance suspended in a solvent - insoluble substance may settle over time, shake bottle vigorously before use to ensure even dispersion

Data sheet - check route of administration
* suspensions should NEVER be given intravenously

Syringes and Needles:

Appropriate syringe volume
- syringe should be the smallest size which is larger than the volume to be injected
- provides the most accurate dose to patient
- still allows you to “draw back” on syringe to check whether you are in a blood vessel

1. Gauge - diameter of needle
   *smaller gauge = larger diameter
2. Length of neeedle - dependent on species and site of injection

Checks:
1. Right patient
2. Right drug
3. Right dose
4. Right route
5. Right time
6. Right frequency

Question 3

LO: Locate the pertinent information found in drug data sheets

Answer 3

Name: Use generic names rather than trade names

Concentration: Must use the correct strength for the patient
- Too strong a conc would result in over-dosage
- Too weak a conc would result in ineffective therapeutic levels of drug

Presentation: Drug appears as it should
- No evidence of contamination or microbial growth
- Supensions/Emulsions: will separate when left on the shelf, must be shaken vigorously to ensure even dispersion and accurate dosage when administered

Indication: Ensure the drug will actually be treating the condition you are prescribing it for.

Dosage and administration: Accurate dose calculation is essential
- Drug must be delivered via its recommended route
- Suspension should never usually be administered intravenously

Contra-indications: Ensuring you’re not using the drug in contra-indicated situations , this could compromise the animals health
- Implications for human health (how will the user be affected by the drug
- Important that the drug is appropriate for the species, age and disease state the animal is in
- FOOD PRODUCING ANIMALS: pay attention to withdrawal periods

Question 4

LO: Demonstrate how to administer a drug via:
>subcutaneous route

Answer 4

1. Identify sites for injection
   - Usually under the skin in the dorsal cervical area (scruff)
   - Anywhere along the back is suitable
   - Fractious patients: can be safer to inject more caudally
2. Have the patient restrained appropriately
   - Should be restrained in sternal recumbency or in sitting or standing position
   - Subcutaneous injections normally well tolerated unless the injectable material is of an irritant nature
3. Ensure hands are clean
   - Good practice to wash hands and apply antiseptic gel between each patient
4. Prepare the injection
5. Loosen the lid of your needle
6. Pick up fold of skin by pinching skin between thumb and finger
7. Insert needle with the bevel facing upwards subcutaneously up to hub
   - Needle should advance easily
   - Resistance: needle inserted intradermally or intramuscularly, should be redirected
   - Needle should be inserted up to the hub to avoid displacement should the animal move
8. Draw back and observe needle hub for blood
   - Ensures that agent will not be injected intravascularly ( some agents can cause a sever reaction and/or death if injected intravascularly )
   - If blood is aspirated redirect the needle

-If air is aspirated you have likely gone through the skin and need to redirect the needle

9. Inject in a moderate controlled fashion
   - Subcutaneous tissue can accommodate relatively large volumes of fluid (30-50mls)
10. Remove needle and syringe, and massage injection site
    - Ensures dispersal of agent and helps alleviate irritation

Question 5

LO: Demonstrate how to administer a drug via:
> intramuscular route

Answer 5

1. Identify the sites for intramuscular injection
   - CANINE: quadriceps muscle group on the anterior thigh, the lumbo-dorsal muscles either side of the lumbar vertebrae or the triceps muscle posterior to the humerus
   - Hamstring muscle group should be avoided due to risk of sciatic nerve damage
   - EQUINE: the superficial pectorals, lateral neck, the gluteals and the semimembranosus and semitendinosus muscles
2. Have patient restrained appropriately
   - Should be restrained in lateral or sternal recumbency, or in a sitting/standing position
3. Ensure hands are clean
   - Good practice to wash hands and apply antiseptic gel between each patient
4. Prepare the injection
5. Loosen the lid of your needle
6. Desensitise the area
7. Insert the needle intramuscularly and rapidly at a 45-90º angle
   - Quick insertion is less painful than slow advancement
8. Draw back and observe needle hub for blood
   - Ensures needle will not be injected intravascularly
   - If blood is aspirated redirect the needle, should be done carefully to avoid moving the needle too much as the animals might react to this
9. Inject material in a moderate controlled fashion
   -Muscle is dense and can’t accommodate large volumes of liquid - 2ml in cats, 3-5mls in dogs
   - Equine muscle can accommodate larger volumes - 10mls in the neck, 20-30 mls in other sites ^
10. Remove needle and massage injection site
    - Ensures dispersal of agent and helps alleviate irritation

Question 6

LO: Demonstrate how to administer a drug via:
> intravenous route

Answer 6

1. Identify sites for intravenous injection and choose a needle of appropriate gauge and length
   - Can be injected into the jugular, cephalic, lateral saphenous or femoral vein
   - Latter two sites less commonly used as they are slightly more challenging, can prove useful if unable to access jugular/cephalic vein
2. Have the patient restrained appropriately and vein raised
   - JUGULAR: Sternal or lateral recumbency, limbs pulled forward, head turned away from injector
   - CEPHALIC: Sitting or sternal recumbency, limb held forward with restrainers hand behind elbow and thumb used to raise the vein
   - LATERAL SAPHENOUS: Lateral recumbency, stifle extended and vein raised by restrainer applying pressure to the distal thigh or proximal tibial segment
   -FEMORAL: Lateral recumbency, uppermost limb abducted to expose medial aspect of lower limb and vein raised by the restrainer by compressing femoral vein on medial side of upper thigh with thumb
3. Ensure hands are clean
   - Good practice to wash hands and apply antiseptic gel between each patient and put on gloves
4. Prepare the injection site aseptically and swab with surgical spirit
5. Identify vein by palpation and stabilise it bye placing thumb of free hand alongside it
6. Hold needle with bevel facing up and insert needle through skin and into raised vein at ~30º to skin
7. Reduce the angle and advance the needle into the vein up to the hub
   - Draw back, dark venous blood should be visible in the needle hub
   - BRIGHT RED BLOOD: you have inadvertently entered an artery (injecting drugs intra-arterially is very dangerous), apply pressure above the injection site and withdraw needle
   - It is essential that the needle is definitely within the vein before any agent is injected. If vein blows it is usually necessary to find a new site
8. If taking a blood sample, keep vein raised and withdraw an appropriate volume of blood
9. If injecting, relieve pressure applied proximally to allow the drug to be injected
   - Inject material in a moderate controlled fashion
   - If injecting large volumes, periodically recheck needle is still within vein by temporarily raising it and withdrawing the plunger slightly
10. Remove needle and apply pressure to injection site using your thumb or a swab
    - Will stop haemorrhage at the injection site

Question 7

Routes of administration

Answer 7

1. Topical: Applied to a particular site e.g.
   >epi-cutaneous (applied to skin)
   >inhalational
   >enema (absorbed via the rectal mucosa)
2. Enteral: Administered via the GI tract e.g.
   > oral/gastric tablets or oral liquids
   > rectal
3. Parenteral: non-oral, systemic administration (injection)
   > subcutaneous (under the skin)
   >intramuscular (into the muscle)
   >*intravenous (into the vein)
   >intraperitoneal (into the peritoneal cavity)
   >intradermal (into the layers of skin)
   > intracardiac (into the heart)

Question 8

Drawing up an accurate dose

Answer 8

1. Firmly attach a hypodermic needle to a syringe of an appropriate volume
2. Swab the top of the drug bottle to remove contaminants and prevent them being drawn up into the syringe
3. Withdraw the correct volume required from the drug bottle

• Drug bottle should be held upside down and needle inserted
• Larger volume than required should be withdrawn and then the syringe flicked to displace any air bubbles to the top
• Air and any surplus drug should then be returned to the bottle
• Ensures the final volume is accurate and there are no air bubbles

4. Detach the needle from the syringe and replace with a new needle of appropriate length and gauge
   - Ensures needle is sharp and sterile
   - Length of the needle should be appropriate for the depth of insertion into the tissue being injected
   - Too long: will bend or pass too deep
   - Too short: won’t reach the area to be injected
   - Gauge should also be appropriate for the viscosity of the drug to be injected
   - Too narrow: the drug won’t inject easily
   - Too large: more painful