The information on this page should be used together with the information on drug absorption provided in Understanding Pharmacokinetics for Pain Management in Ruminants

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• In ruminants, orally administered drugs are often given as a bolus or as a drench.
• In-feed administration is a simple method for administration of a drug. (B10.51.w34)
  • Absorption is relatively slow and a long time (an hour or more) may be required for the drug to have the desired effect. (B10.51.w34)
  • If medicated feed is refused or only partially eaten then the required dose will not have been administered. (B10.51.w34)
• In-feed administration may be the most appropriate method appropriate for long-term administration of NSAIDs such as aspirin and phenylbutazone in ruminants.
  • Such use is not likely to be appropriate for food-producing domestic ruminants, however it may be of use for example in treatment of chronic arthritis in non-domestic ruminants in zoos, or in pet ruminants which will not enter the human food chain.
  • Palatable drugs should be used if they are to be concealed in food. (B10.51.w34)
• Absorption of drugs following oral administration is generally considerably less than 100% and may be very variable between species and even between individuals. 
  • The time to effect following oral administration is delayed by minutes to hours. (B323.7.w8)
  • In ruminants the rate of absorption may be markedly affected if closure of the oesophageal groove takes drugs directly to the abomasum, bypassing the rumen. 
  • Absorption may also be affected by administration with food (J21.44.w2) although this effect may be less variable in ruminants than in monogastric species such as horses.
  • Drugs may be destroyed in the digestive tract, or may pass through without being absorbed. (B10.6.w38, B323.7.w8)

Dose rates for oral administration are generally higher than those for parenteral administration of the same drug, to allow for the reduced absorption and/or the first-pass effect (metabolization of drugs as they travel through the hepatic portal system). (B323.7.w8)

• Understanding Pharmacokinetics for Pain Management in Ruminants - Oral Administration of Drugs

• Intravenous administration of drugs in ruminants is usually into the jugular vein. (V.w5)
• This route of administration is not suitable in circumstances where restraint of the patient is either not possible or not appropriate, which may occur with non-domestic ruminants. (V.w5)
• Injection can be painful and involves a risk of infection. (B323.7.w8)
• As well as giving the fastest onset of action, this route also results in the fastest elimination from the system, therefore repeated injections are required if plasma concentrations of a drug are to be maintained. (B323.7.w8)

• Understanding Pharmacokinetics for Pain Management in Ruminants - Major Parenteral Drug Administration Routes

• This is usually the second fastest route for drugs to reach the systemic circulation. 
• This route also allows the administration of "depo" injections which are absorbed slowly to give a prolonged period of action.
• Intramuscular injection can be painful. (B323.7.w8, J307.40.w1)
• Injection  involves a risk of infection. (B323.7.w8)
• Absorption following intramuscular injection may be variable. (B323.7.w8)
• Intramuscular injection results in peaks and troughs in the blood concentration of the drug.  (B323.7.w8)
• Muscle damage may occur following injection of drugs; the amount of damage varies with the drug preparation injected (J307.40.w1). Repeated injections of some drugs may result in tissue necrosis.  (B323.7.w8)

Intramuscular administration in non-domestic ruminants may be carried out by hand injection if circumstances allow but may also be carried out using a pole syringe, in which the operator only has to approach within a couple of metres of the animal, and by remote injection (darting).

Hand injection

• This is the usual means of administering an intramuscular injection in domestic ruminants. 

Limitations:

• Requires close approach and that the animal stays reasonably still for the period of time during which the drug is administered.
  • This may be stressful for non-domesticated individuals including semi-free-range individuals of domesticated species. (V.w5)
  • There is a risk of injury to animal and administrator during restraint of non-domesticated individuals. (V.w5)
  • This is often not practical for non-domestic ruminants, except in particularly docile individuals. (B10.51.w34)

Pole Syringe

• A pole syringe is basically a syringe attached to a long pole, designed so that the contents of the syringe can be injected while the operator remains at a distance (the length of the pole, e.g. two metres) from the animal. (B10.51.w34, B345.3.w3)
• This method may be safer and more practical than hand injection when dealing with non-domestic animals or animals which are not used to being handled. (B10.51.w34, V.w5)

Limitations:

• This method is only appropriate if the animal can be reached, e.g. if it is within a confined space (or is held by a trap or by entanglement in a stationary object) and cannot retreat further away than the pole can reach. (B10.51.w34, B345.3.w3)
• It is usually only possible to administer about 10 ml or less of a drug, since animals will generally not stay still for long enough to inject larger volumes. (B345.3.w3)
  • If the animal jumps away before the total dose has been administered then a second injection is required. (B10.6.w38)

Remote injection (darting)

• Remote injection is not commonly used for drug administration to fully domesticated ruminants, however this is an important method of drug administration for non-domesticated animals, both captive and free-living. (B10.51.w34)
  • Smaller species  should be injected into the rump or the back of the hind leg. For larger species these sites may be used also, but the neck or shoulder are possible as alternatives. (B10.51.w34)
• The main advantage of remote injection is that it allows injection at a distance. (V.w5)
  • Handling and restraint are not required, and the stress associated with these is avoided. (V.w5)

Limitations

• Limitations of remote injection include all the normal limitations for intramuscular injection, as well as the points listed below.
• There is always a risk of injuring the animal. (B345.3.w3)
  • Small antelope and deer have thin skin which is easily penetrated by a dart; care is required to avoid excessive impact force of the dart hitting the animal. (B10.6.w38)
• This method is only suitable for relatively small volumes due to limits in the capacity of individual darts. (B10.6.w38)
  • When darting small individuals there are also limitations on size of dart and volume related to the trauma associated with impact of darts, which is greater with larger, heavier darts and with higher impact velocity. (B345.3.w3)
• This method has limited applicability for injection of viscous drugs, particularly when using gas-pressurised syringes, as there is an increased risk of incomplete injection. (V.w5)
• An animal may be stressed by being hit by a dart. (V.w5)
• An animal may react badly to being hit by a dart and injure itself e.g. by running into an obstacle, or aggravate an injury such as a foot or leg problem by running. (V.w5)

• Understanding Pharmacokinetics for Pain Management in Ruminants - Major Parenteral Drug Administration Routes

• Absorption is generally slower than with intramuscular administration and the time to effect after subcutaneous injection is relatively long. (B323.7.w8)
• Absorption from the injection site is variable. (B323.7.w8)
• Absorption from subcutaneous sites may be greatly decreased in individuals in shock. (B327.7.w7)
• Injection can be painful and involves a risk of infection. (B323.7.w8)
• This route is not suitable for the injection of irritating drugs. (B323.7.w8)

Administration by Needleless Injector

• Administration of drugs using a needleless injector could provide an effective method for administration of local anaesthetics prior to management procedures such as lamb castration and tail docking, without the risks (e.g. of introduction of infection) associated with injection by needle and syringe. (D153, J35.155.w1)
• Local anaesthetic has been administered using a high-pressure needleless injector (Syrijet, Keystone Industries) in experimental conditions for reduction of pain associated with castration and tail docking of lambs. It was noted that there were considerable limitations in the volume of drug which could be held in the injector, requiring frequent, time-consuming reloading with relatively expensive drug ampules, and in the maximum volume which could be injected at one time (0.03 ml with this applicator). [1998] (J35.155.w1)

• Understanding Pharmacokinetics for Pain Management in Ruminants - Major Parenteral Drug Administration Routes
• Pain Prevention for Lamb Castration and Tail Docking

• Transdermal administration of drugs using patches is advantageous in ease of administration, being noninvasive, and allowing continuous delivery of a drug over an extended period. (B323.7.w7, P56.1.w4)
• Absorption may vary depending on temperature, skin pH, local blood flow, stratum corneum permeability and skin fat content. (J13.60.w1)
• Transdermal delivery of a drug requires that it be lipid soluble and capable of crossing the stratum corneum and epidermis to enter the dermis and be taken up by the microcirculation to reach the general circulation. (B323.7.w7)
• Transdermal absorption is very variable. (B323.7.w7)
• There is a time delay between application of the patch and the drug reaching the general circulation, and drugs in a patch are delivered at a constant rate, therefore time is required for the drug to reach a steady concentration in the body; there is a significant delay between application of the patch and a therapeutic systemic concentration being achieved. (B323.7.w7)
  • The time to achievement of therapeutic concentrations could be eliminated by administration of an intravenous loading dose at the time of application of the patch. (B323.7.w7)

Examples of the use of transdermal administration of drugs in ruminants include:

• Application of EMLA cream (Astra Pharmaceuticals Ltd.) has been used in experimental situations to reduce pain associated with venupuncture in lambs (to avoid interference with other pain measurements). (J21.66.w1)
• Transdermal administration of fentanyl in sheep using a patch has been carried out experimentally for the relief of pain following orthopaedic surgery. It was found to be more effective than oral phenylbutazone as indicated by lower plasma cortisol levels, greater mobility and more normal flock behaviour. (P56.1.w21)
• Transdermal administration of fentanyl in goats in one study found that, as for cats and dogs, considerable variation in achieved plasma concentrations were noted and it was considered that delivery from the patch was not consistent. (J13.60.w1)

• Understanding Pharmacokinetics for Pain Management in Ruminants - Other Drug Administration Routes

• Topical administration is commonly used with local anaesthetic drugs to provide surface anaesthesia of the nose, mouth, ear, bronchial tree (by spray), cornea (by drops), urinary tract or rectal mucosa. (B327.43.w43, B322.3.w3, J213.4.w1)
• Intramammary infusion is a special case of topical treatment. It is used mainly for administration of antibiotics in the prevention (dry cow therapy) and treatment of mastitis, but is also used for administration of corticosteroids, usually together with antibiotics, in mastitis treatment. 
  • Intramammary infusion of local anaesthetic solution can be used for analgesia of the mucosa of the teat cistern. See: Local Anaesthesia of the Teat in Ruminants
• Intranasal administration has been used experimentally in sheep for the administration of buprenorphine. It gave a high bioavailability and rapid absorption. (J309.205.w1)

• Local Anaesthesia of the Teat in Ruminants
• Understanding Pharmacokinetics for Pain Management in Ruminants - Other Drug Administration Routes

• One form of regional anaesthesia/analgesia is epidural anaesthesia. This involves injection into the epidural space just outside the spinal cord. 
  • This is a technically difficult technique requiring practice for correct use. (D153, J15.13.w4) 
  • Strict asepsis must be employed when this technique is used in order to avoid infection of the epidural space. (B121.20.w20)

• Antler Pedicle Block
• Caudal Epidural Anaesthesia of Cattle
• Caudal Epidural Anaesthesia in Sheep
• Cornual Block in Cattle
• Cornual Block in Goats and Sheep
• Line Block in Ruminants
• Intravenous Regional Anaesthesia of the Lower Limb - Cattle
• Intravenous Regional Anaesthesia of the Distal Limb in Sheep and Goats
• Inverted L Block in Ruminants
• Local Anaesthesia of the Teat in Ruminants
• Lumbosacral Epidural Anaesthesia in Cattle
• Lumbosacral Epidural Anaesthesia in Sheep and Goats
• Regional nerve blocks of the foot in Cattle
• Peronial and Tibial nerve block of sheep and goats
• Paravertebral Block in Ruminants
• Ring Block of the Lower Limb of Ruminants
• Understanding Pharmacokinetics for Pain Management in Ruminants - Other Drug Administration Routes
• Assessment of Pain in Ruminants