Equine Medications and Principles of Drug Administration 2024 PDF

COURSE: EQUINE MEDICINE(VMD VI) Topic: Equine medications and principles of drug administration DR. O.O. AKINNIYI University of Ibadan, Department of Veterinary Medicine 1 ...

COURSE: EQUINE MEDICINE(VMD VI) Topic: Equine medications and principles of drug administration DR. O.O. AKINNIYI University of Ibadan, Department of Veterinary Medicine 1  INTRODUCTION Drug administration to equids is a routine daily task for veterinarians, but care must be taken to do it correctly every time. All drug administration routes have the potential for negative consequences. Veterinarians can have a large positive impact on equine welfare by ensuring that medicines are administered properly. When using any drug, ask the following questions: 1. Is it the correct drug? 2. Is it the correct dose? 3. Is it the correct route? 4. What are the possible complications? Equine meds & principles of drug adm. by Dr. O.O Akinniyi 2  Drug Dosage Form Oral dosage forms: Refers to administration of drug through the mouth. Oral dosage forms include liquids (solutions, suspensions, emulsions, elixirs, and syrups), semisolids (pastes), and solids (tablets, capsules, powders, granules, premixes, and medicated blocks). Parentral dosage forms: They are sterile solutions or suspensions of drug in aqueous or oily vehicle. External dosage form: 1) Ointment- semisolid preparation for external application. 2) Cream- a viscous semisolid, consisting of oil in water emulsion or water in oil emulsion. 3) Dusting powder e.g., popular antibacterial agent applied on animal wounds. 4) Lotion- an aqueous solution or suspension for local application. 5) Spray-a drug applied in liquid form by pressure. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 3  Route of drug administration Oral administration Parenteral administration (IV, IM, SC, Intra articular, epidural) Topical or local application Equine meds & principles of drug adm. by Dr. O.O Akinniyi 4  ORAL ADMINISTRATION Drugs given by mouth are designated as ‘Per Os’ (p/o or PO). There are large numbers of pharmaceutical preparations available for oral administration and they are given directly into the mouth or mixed in feed. Other routes of oral administration include using nasogastric tube or drench technique. Always ensure that the handler is competent and that the person administering the drug has the equipment and drug ready to ensure that the procedure is as short as possible for the animal. The head will need to be raised until the animal swallows to ensure that the drug is ingested. Ensure there is no food in the mouth before starting the administration technique. Ensure the full dose is consumed; if any amount of drug is lost or dropped from the mouth, re-dosing will be necessary. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 5  Administering tablets or powder Two techniques are as follows: 1. Form a paste by mixing the powder with water. Draw this mixture up into a plastic syringe. Raise the head, open the mouth and deposit the drug on the back of the tongue Close the mouth and keep the head raised until the drug has been swallowed. 2. Roll a bolus by mixing tablets or powder with available palatable substances (feed). Offer the mixture to the animal to eat and supervise until finished. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 6  Administering paste Restrain the head of the horse to prevent pulling back. Ensure that the horse’s mouth is empty so that the horse will not spit out the paste along with a clump of food. Insert the syringe into the horse’s mouth through the inter-dental space and depress the plunger. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 7  Administering liquids A. Drenching Drenching is the technique of administration of liquid products directly into the back of the mouth and down the throat. This can be done using oral dosing syringe or drench gun. This carries a risk of aspiration pneumonia Never pour liquids directly into an animal’s nose: this will result in severe inflammation of the nasal cavity and pharynx and most likely result in aspiration pneumonia. The following drugs are available as preparations for drenching: 1. Antacids (magnesium carbonate and sodium carbonate, and omeprazole) 2. Laxatives (magnesium sulphate) 3. Anthelmintics (fenbendazole, oxfendazole, ivermectin) Equine meds & principles of drug adm. by Dr. O.O Akinniyi 8  Administering liquids contd B. Nasogastric (stomach) tube insertion Indication Direct hydration of intestinal contents (e.g., treating impaction colic) Providing enteral nutrition when the horse can't or won't eat Gastric decompression to relieve excess gas and fluid Administration of fluids and medications Relieving esophageal obstructions Gastric lavage in cases of suspected toxin ingestion Equipment required Stomach tube designed for equids. Lubrication (lidocaine gel, water-soluble gel or any other lubricant at tip of nasogastric tube). Stomach pump or funnel that adapts to end of the tube. Two buckets: one empty, one with a premeasured amount of warm water. Liquid (e.g. water, electrolyte solution, fluids, mineral oil), medication or nutritional support to be administered. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 9  Administering liquids contd B. Nasogastric (stomach) tube insertion contd Restraint and positioning Sedation and/or application of a twitch may be necessary. Preferably, stand on the left side of the horse’s head Equine meds & principles of drug adm. by Dr. O.O Akinniyi 10  Administering liquids contd B. Nasogastric (stomach) tube insertion contd Procedure 1) Mark the tube with an indelible marker to record the approximate distance from the nostril to the pharynx. It can be estimated by measuring the distance from the nostril to the lateral canthus of the eye 2) Lubricate several inches of the outside of the tube. Lubricate with liquid paraffin, water or obstetrical lubricant. 3) Standing to the left side of the patient, place the right hand on the horse’s nose, and using the thumb, move the alar fold of the nostril dorsally. 4) Using the left hand to guide the NG tube ventrally and medially into the nasal passage (either left or right can be used), taking care to avoid the middle meatus and lateral meatus, the tube should be advanced firmly but not forced. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 11  Administering liquids contd Procedure contd 5) Once the tube reaches the pharyngeal area, swallowing is required to advance the tube into the esophagus. Be prepared to quickly advance the tube down the esophagus several inches when the horse swallows 6) Correct positioning of the tube in the esophagus must be assessed before any liquid is placed into the tube. This can be done by: Detecting negative pressure on the tube when applying suction Visualizating or palpating the tube on the left side of the neck as it passes down the esophagus. Noting the increased resistance to passage of the tube into the esophagus as compared to that of the trachea Equine meds & principles of drug adm. by Dr. O.O Akinniyi 12  Administering liquids contd B. Nasogastric (stomach) tube insertion Procedure contd (7) Once in the esophageal lumen, advance the tube to the stomach. Judging by the length of tube passed, one can estimate that the stomach has been reached. Mild resistance may be encountered at the cardia. If gentle pressure or blowing into the tube does not allow passage into the stomach, instillation of 10 ml of lidocaine in 50 ml of water into the tube may cause relaxation of the cardia. (8)If the purpose of the nasogastric intubation is administration of fluid, mineral oil or any kind of medication or supplement, the appropriate amount of liquid, medication or gruel should be administered, followed by an amount of water sufficient to push all the medication out of the tube and into the stomach. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 13  Administering liquids contd Procedure contd (9)If the nasogastric tube is to be maintained as an indwelling tube for continuous or intermittent reflux of gastric contents, or administration of liquids, the end should be taped to the horse’s halter. (10) To remove the tube, obstruct the lumen of the tube by placing a thumb in the end of the tube or folding it over Note: If medicating with liquid paraffin this will run in more easily if mixed with warm water Equine meds & principles of drug adm. by Dr. O.O Akinniyi 14  Nasogastric intubation Supplies needed for the procedure Equine meds & principles of drug adm. by Dr. O.O Akinniyi 15 Nasogastric intubation The distance from the nostril to the pharynx can be approximated by measuring the distance from the nostril to the lateral canthus of the eye. The tube can then be marked to indicate its location after insertion into the nose Equine meds & principles of drug adm. by Dr. O.O Akinniyi 16  Nasogastric intubation Equine meds & principles of drug adm. by Dr. O.O Akinniyi 17  Nasogastric intubation Equine meds & principles of drug adm. by Dr. O.O Akinniyi 18  How to manage possible complications of using a stomach tube 1) Nosebleed (epistaxis): This is a common complication, especially if the animal moves its head a lot, the tube is too big or is not in the ventral meatus. It looks alarming but will stop in a short time. Keep the animal quiet until the bleeding stops. 2) Aspiration of fluid into the lungs: This is a much more serious complication compared to epistaxis. It can occur if the tube is placed in the lungs instead of the stomach, and can result in death within minutes. Alternatively, despite correct placement of the tube, careless or overzealous fluid administration or tube removal may still result in some of the fluid entering the lungs, causing aspiration pneumonia. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 19  Parenteral: Injections Gives swift, effective and highly predictable blood concentration and allows rapid modification of dose and is used for emergency treatment. All injections carry a risk of infection and can cause pain, fear and distress to some extent. They should never be given unnecessarily. The following rules apply for all injections: 1) Always use a sterile syringe and needle to avoid creating an injection site abscess. Wipe the top of the medicine bottle with surgical spirit if it is dirty. 2) Always use the narrowest gauge (G) that allows smooth injection of the drug, i.e. 20G or 21G for watery drugs and vaccines, 16G or 18G for oily drugs or suspensions. 3) Always ensure the injection site is clean and free from mud or dirt. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 20  Subcutaneous injection Ensure that the drug is formulated to be given subcutaneously. Many drugs are poorly absorbed from subcutaneous tissue or can give a bad reaction, especially if large volumes are given. Any skin site may be used, but preferred areas are the neck and pectoral regions where there is looser skin covering the body. Using a short needle (one inch), pinch the skin and introduce the needle almost parallel to the skin surface to avoid placement in underlying muscle, there should be little resistance to injection. The depot of drug under the skin leaves a small swelling, which disappears as the drug is absorbed. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 21  Intramuscular injection Ensure that the drug is formulated for intramuscular use. Some drugs cause severe inflammation when injected intramuscularly. As a precaution never give more than 10 ml in any one site. Malignant oedema is a rare, often fatal, infection caused by Clostridial bacteria, typically caused by activation of dormant spores within the muscle; a possibility if IM injections are not given cleanly and carefully or if an irritant drug (e.g. flunixin meglumine) is used. Ensure a competent handler and consider the safety of the handler, the animal and the administrator of the drug at all times. Ensure that all drugs are ready and drawn up and all equipment (needles and syringes) are sterile. Suitable needles for IM injections in equids are 18–21G depending on the viscosity of the solution (e.g. 18G for penicillin). The length of the needle for adult horses and mules and well-muscled adult donkeys should be 1.5 inches, for foals and thin donkeys one inch would suffice, to inject the drug deep into the muscle mass. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 22  Intramuscular injection contd There are three preferred sites for intra-muscular injections: 1. Neck – in the triangle of muscle demarcated by the nuchal ligament, the dorsal border of the cervical spine and the cranial border of the scapula. As a precaution never give more than 10 ml in any one site. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 23  Intramuscular injection contd (2) Gluteal muscles – in the centre of the muscular square bordered by the tuber coxae, tuber ischii, sacrum and base of tail. As a precaution never give more than 10 ml in any one site. For gluteal injections ensure safety when administering the injection by maintaining body position as close to the animal as possible; use a spare hand on the animal’s body to detect sudden movements. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 24  Intramuscular injection contd 3. Pectoral muscle (horses only) – in thickest part. Maximum volume is 5 ml per site and do not inject potentially irritating drugs in this area as it will affect movement. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 25  Intramuscular injection contd 4. Semitendinosus (Hamstring) muscle: The semitendinosus muscle is part of the hamstring group, located on the back of the horse's thigh. The injection site is in the fleshy part of this muscle, approximately midway between the point of the buttock (tuber ischii) and the point of the hock. It's generally recommended not to exceed 10 ml per injection site. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 26  Intravenous injection Ensure that the drug formulation is suitable for intravenous use. Many drugs (including almost all suspensions and some oily preparations) cause severe systemic reactions or death when injected by this route. Check that the drug is within the expiry date and contains no particles or contamination. The correct site for IV injection is the cranial third of the jugular vein, where there is less risk of hitting the carotid artery. Inject slowly over 5–10 seconds. Do not inject drugs into the carotid artery Always ensure that a competent handler is present and use safe positions when injecting. Ensure all drugs are drawn up ready in syringes and all equipment is sterile. Suitable needles for IV injection are 21–18G, the larger for more viscous or larger quantities that need administering more quickly; a 19G would suffice for most routine IV injections. A 1–1.5-inch length needle can be used depending on the size of the animal. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 27  Possible complications of intravenous injection 1. Intra-arterial injection 2. Peri-vascular injection 3. Phlebitis/thrombophlebitis Equine meds & principles of drug adm. by Dr. O.O Akinniyi 28  Relationship between carotid artery and jugular vein Equine meds & principles of drug adm. by Dr. O.O Akinniyi 29  Intra-articular injection Introducing a needle into the joint of a working equid may occasionally be necessary in order to: 1) take a sample of synovial fluid from a joint, if infection (septic arthritis) is suspected 2) flush an infected joint 3) inject antibiotics into an infected joint 4) inject anti-inflammatory drugs into an inflamed joint. Aseptic preparation and knowledge of anatomy is paramount to avoid creating unnecessary harm. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 30  Epidural injection In horses, administering a caudal epidural anesthetic into the sacrococcygeal or first intercoccygeal space provides regional analgesia to the tail and perineum, thus facilitating surgical procedures of the vagina, cervix, urethra, bladder or rectum, as well as select cases for correction of a prolapsed uterus; it is also helpful for managing dystocia. Equine meds & principles of drug adm. by Dr. O.O Akinniyi 31  Topical or local application It refers to external application of drug to the body surface for localized action at accessible site, such as skin, eyes, and body orifices Equine meds & principles of drug adm. by Dr. O.O Akinniyi 32