CH 25- Pharmacology Notes - Antimicrobial Agents   (Antibiotics) pp. 834-838 

A. Antimicrobial Agents 

     -antibiotics initially produced by microorganisms, which destroy OR

       inhibit growth of other microorganisms 

     -kill life-threatening infections 

     Can be produced chemically 

B. Antibiotics Specific 

     -each antibiotic effective against specific groups of microorganisms

     -some are BACTERICIDAL: destroy bacteria 

     -some are BATERIOSTATIC: inhibit bacteria growth

     **some antibiotics are BOTH bactericidal AND bacteriostatic 

     -species of bacteria affected by antibiotic= SPECTRUM 

     (broad spectrum antibiotics are effective against a wide range of microorganisms) 

      G+ and G-

C. Classifying Bacteria- Gram Stain 

     -ability of bacteria to absorb dye (Gentian violet) into the cell wall 

     -GRAM stain results: 

      G+   (absorb dye-dark blue cell walls) 

      G-    (do NOT absorb dye-light pink cell walls) 

D. Effective Antibiotic 

     -must be able to reach site of infection 

     -concentration must be maintained over period of time to destroy ALL bacteria OR

       inhibit bacterial growth so natural defenses can take over 

     **Length of antibiotic therapy depends UPON: the microorganism (pathogen),

         site of infection, duration of infection 

      -Minimum length of antibiotic therapy is usually 5 days 

     -stopping an antibiotic too soon may cause under-exposed pathogens to become

      resistant to the antibiotic 

     **Nosocomial antibiotics are antibiotics which originate in a clinical setting 

E. Choices of Antibiotic Treatment   

     -BEST: culture bacteria (grow on petri dish, then test several antibiotic discs) 

                   **if bare space occurs-bacteria sensitive to antibiotic patch(disc) 

    -HOWEVER: sometimes time/money a concern-treat with antibiotic which seems the 

      BEST: Empiric Treatment

**WHEN selecting an antibiotic, one should, chose an antibiotic which destroy/inhibit the pathogen BUT NOT DISTURB the normal bacterial flora (good bacteria in body) 

WHY would you not want to harm the normal-existing flora of bacteria? 

CAREFUL: Over-use of potent broad-spectrum antibiotics can lead to resistant strains of bacteria 

Name: _______________________                                      Date: ________

                                               ANTIBIOTICS 

**Erythromycin 

**Azithromycin                                    

NOTES: CH 15 DISEASE PREVENTION –pp. 242-244

A. Animals resistant to disease because of:   

    - immunity

    -good nutrition

    -skin/mucous membranes protect from invading pathogens

    - normal bacteria flora-inhibit growth of other organisms

    -adhesion sites-pathogen must adhere to animal’s cells before infection begins

B. How to maintain normal bacteria flora: 

    -reduce stress (see below) 

    -proper nutrition 

    -medication

C. Stress in animals: 

     -stress considered a threat/animal (animal increases epinephrine and cortisol production)

     **cortisol can help animal in stress ( increases carbohydrate metabolism, more glucose to brain, reduces inflammation to damaged tissue) 

     ***adverse effect of cortisol- weakens immune system, increases risk of diabetes, muscle weakness) /Cushing’s Disease-(hyperadrenocorticism) = CHRONIC elevated cortisol levels

     -stress increases activity of sympathetic nervous system

     D. Nutrition and Stress: 

    -nutrition maintains immune system  

          Vitamins (ex. Vitamin E) and minerals (ex. selenium) keep immune system strong

          Antioxidants (oxidation-inhibiting vitamins/minerals0 play role in healthy immune

            system    

     -sudden changes in diet: (decrease normal flora in intestinal tract)

                                                allows for pathogen invasion

          **flora = good bacteria                pathogen = bad(disease-causing bacteria) 

           **antibiotics can decrease normal flora-CAREFUL 

                                                                                                                                p. 2 

E. Other forms of stress in animals: 

    -over-crowding: increases competition for food and comfort, animals too close

                                                                                                       (spread diseases) 

    -increased urine/feces contaminate animal’s environment 

    -humidity higher in crowded areas/allows pathogens to survive outside body 

     **VENTILATION: air exchanged from inside of building to outside 

           Without ventilation- animals exhale (add heat, moisture, pathogens to air) 

                                          Ammonia/hydrogen sulfide released from urine/feces 

          **the above irritate mucous membranes of animals, LOWER respiratory tract defense systems/easier for pathogens to invade respiratory tract 

     ALSO: without ventilation-animals stir up dust which carries pathogens and irritates respiratory tract 

F. HOW to prevent Disease- FRESH AIR 

     -bring fresh air from outside INTO inside barn area; reduce moisture, dust, etc. 

     VENTILATION methods:  

     1. some barns built for natural air flow (IN/OUT) 

     2. some barns use fans to move air/keep clean

     3. some barns, fans on ONE end of barn, air outlets on OPPOSITE end = TUNNEL VENTILATION (a breeze of 3-5 miles/hour can be created) 

**PROBLEM- in cold weather, less air exchange can take place (heat issues) BUT..

     At least 4 air exchanges per hour should STILL take place 

     In summer, up to 30 air exchanges may be necessary 

G. OTHER: 

     -older animals, have a higher level of immunity than the young (WHY?) BUT..

          older animals could be carriers for pathogens-THEREFORE: 

     **IDEAL air flow in barns should flow from the youngest to the oldest-

         (young animals not exposed to possible pathogens exhaled by older animals)

     **ALSO: young animals should not mingle with older animals 

Pharmacology- CH 25- Addendum Notes

Treatment of Internal Parasites 

ANTHELMINTICS (de-wormers) -IMPORTANT 

    -parasites SHORTEN life span of animal 

    -parasites REDUCE quality of life for host 

**Current anthelmintics eradicate the parasite and are less toxic to host

     Also more convenient to give since come in chewable and paste forms

Some types of Anthelmintics: 

     A. Benzimidazoles- large class of anthelmintics which interfere with parasite

            metabolism

               1. Albendazole- fights liver flukes (flatworm in liver) 

               2. Fenbendazole/Mebendazole- used in small animals to eradicate

                    roundworms, hookworms, whip worms and SOME tapeworms

     **NOTE-Adverse effects (toxicity) not usually seen at recommended dosages

     B. Organophosphates- affect neurotransmitters (ACh ) of parasites 

           (Ex. Trichlorfon)-can be dangerous to humans 

          Signs of toxicity- salivation, breathing difficulties, vomiting, muscle effects

          Treatment: Atropine 

     C. Tetrahydropyrimidines: effective against adult nematodes, not effective against

                                                   larvae   

               1. Morantel- used in sheep and cattle (feed additive) 

               2. Pyrantel- horses: pinworms, strongyls, ascarids(round worms) 

                                    Dogs:   hookworms, ascarids 

                **NOTE: Safe and non-toxic at recommended doses 

     D. Imidazothiazoles- used in most species to treat parasites (equine as well) 

                                         Product packaged as (Drontal Plus, Bayer)  

     E. Milbemycins- paralyze parasites-

               1. Moxidectin- oral dewormer/boticide for horses

               2. Doramectin- injectable drug /treats roundworms and arthropod parasites

                                         in cattle and swine   

                                                                                                                                 p. 2 

     F. **Ivermectins- paralyze nematodes by blocking motor neuron transmission 

               -used in a number of animal species against a wide variety of internal/external

                 parasites     

          Cattle, swine, sheep, goats: injectable ivermectin treats roundworms,

                                                       lungworms, cattle grubs, sucking lice, mites

                                                       paste/oral liquid forms treat strongyls,

                                                       pinworms, bots

           Dogs/cats-mainly used to prevent heartworm, but higher dosages used to treat

            Scabies(skin mites) 

     **CAREFUL- Pure-bred collies tend to be sensitive to ivermectin, therefore, careful

                              dosages must be used

          Over dose symptoms-blindness, ataxia, death 

****Heartworm Treatment**** 

          AVMA recommends the following treatment strategy: 

                   -eliminate adult heartworms first (in heart tissue) THEN 

                   -eliminate microfilaria (immature heartworm which migrate) 

                   -before starting HW preventive, a dog must be free of adult and microfilaria 

          Treatment: melarsomine dihydrochloride (arsenic agent)

                             given by deep IM injection 

           CAREFUL: cage rest required to risk of blood clots (esp. in lungs)

                                Severe reactions may occur: abdominal bleeding,

                                                                              hematuria, tachypnea,

                                                                              icterus(yellowing of skin) 

****Heartworm Prevention**** 

     Ivermectin/Milbemycin-given ONCE a month/if more than 45 days between treatments, RETEST for Heartworm    

      1. Milbemycin- (Interceptor by Novartis)        2. Ivermectin/Pyrantel (Heartgard Plus)

                                                                                         by Merial –fights hookworms too

      3. Moxidectin (ProHeart, Fort Dodge)

           paralyzes adult heartworm/larvae in dogs 6 months or older/injectable-last 6 mos

NOTES- CH 25- Pharmacology- Addendum: pp. 829-831 

I. Diuretic and Cardiovascular Drugs 

     -prevent reabsorption of sodium (Na) and Water

     -increase urine output and sodium excretion 

A. Diuretics- relieve fluid in tissue (edema) 

                        used for kidney, heart, liver diseases

          1. Furosemide (Lasix)- prevents sodium (Na) and chloride (Cl) to reabsorb

                                                 back into the kidney 

                              Effect: rapid, produces loss of fluid (diuresis) within 5 minutes

                                           of IV injection   

                              Forms: oral, injectable 

                   **CAREFUL: lowers potassium (K) levels in blood serum- MONITOR 

          2. Mannitol-produces diuresis 

                              Form: injectable 

                   **CAREFUL: produces crystals in bottle, dissolve crystals before

                                            administering-warm water bath

 B. Cardiac Glycosides- most potent, hazardous, used to treat heart disorders 

                    **CAREFUL-calculate, administer, observe patient OR death could

                                             result 

            1. Digoxin-used to treat chronic heart failure (CHF) -esp. dogs and cats 

                           Form: oral, tablet, liquid, injectable 

                           Effect: reduces heart’s demand for energy/oxygen 

                    **CAREFUL- over dose can be toxic, especially to those with existing

                                             liver/kidney problems  

                       symptoms of overdose: vomiting, diarrhea, loss of appetite, depression

                                                                                                                                 p. 2

    C. Antiarrhythmia Drugs

               1. Quinidine- used to treat arrhythmias in horse/large dogs 

               2. Lidocaine-used as a local anesthetic, can treat ventricular tachyarrhythmias

     **CAREFUL- ALL antiarrthymia drugs are toxic to heart 

          TOXICITY SYMPTOMS: 

          -horses: anorexia, colic, diarrhea, edema of nasal mucosa, dyspnea, laminitis 

          -dogs: vomiting, depression, lack of coordination, convulsions 

      ***NOTE: Lidocaine if given IV in large dosages, drops blood pressure 

   D.  Angiotensin Converting Enzyme Inhibitors (ACE) drugs 

          -vasodilators (enlarge blood vessels) 

          -primarily used to treat canine CHF 

               1. Hydralazine- used to treat CHF in small animals (esp. mitral valve) 

                      **side-effect: sodium/water retention-SHOULD be given with a

                                              diuretic 

               2. Pimobendan- new drug on market to treat CHF 

Neuropharmacology -Addendum

Overview: CNS includes brain and spinal cord

                   CNS divided into: 

                                                Autonomic Nervous System- (involuntary) 

                                                Somatic (motor) Nervous System (voluntary)    

                   Neurons relay information from CNS to rest of body using NT’s

                                                                                                            (neuro-transmitters) 

                   ACh is a neurotransmitter

I. AUTONOMIC DRUGS- 

     A. Cholinomimetic Agents: (mimic ACh)   

           1. Bethanechol- smooth muscle stimulant (ex. stomach, intestines, bladder) 

                -side affects: vomiting, diarrhea, salivation, anorexia 

                 -over-dose: arrhythmias, hypertension, asthma 

           2. Cholinesterase inhibitors-prevent ACh from breaking down, -exaggerated

                 (used mostly to treat internal/external parasites) OR restore rumen/GI tract

                   back to normal after surgery)

                 -over-dose: nausea, vomiting, diarrhea, salivation, sweating,

                                     increased bronchial secretions, bronchospasms,

                                     cardiac arrest, muscle cramps, weakness 

     B. Anticholinergics; (inhibit/stop action of ACh) 

           1. Atropine- derived from belladonna plant, stop ACh

                -effects: decrease salivation/bronchial secretions (low doses) 

                               Decrease movement in GI/urinary tract (high doses)

                **used to dilate (open) eye pupil 

                    used to treat poisoning from insecticides/parasiticides/mushrooms

 C. Neuromuscular Blockers/NMB’s: (paralyze skeletal muscle) 

          1. Vecuronium/Atracurium- newer  

               -effects: relax skeletal muscles, used with surgical anesthesia 

               -overdose: respiratory paralysis 

D. Sympathomimetics: (affect sympathetic nervous system = heart rate, blood pressure,

                                          bronchial airways) 

          1. Epinepherine- (released from adrenal gland when stressed) –FIGHT or FLIGHT 

               -effect(treats): allergic reactions, bronchospasms, cardiac issues

               **not available in oral forms-destroyed by stomach acid 

                   Short-acting 

          2. Isoproterenol- used as bronchodilator, cardiac stimulant 

E. Phenothiazines:   (used as sedatives/tranquilizers) 

          1. Acepromazine- (takes “the edge off”) 

              -used to prolong effects of anesthesia, reduces anxiety/motion sickness 

               **prolonged use may promote seizures in dogs 

F. Others: 

           1. Xylazine-used widely in horses/cattle-sedative and analgesic

                **CAREFUL: Causes muscle tremors, respiratory changes in horses  

                                          Cattle extremely sensitive-require 1/10 dosage used in horses 

                In dogs/cats-causes immediate vomiting 

           2. Propofol- used to introduce anesthesia, (5-10 minutes-metabolized quickly) 

              **CAREFUL: weakens muscular contractions, esp. respiratory actions 

G.     Steroids: (extremely active, effect all organ systems) 

              -used to treat inflammation/auto-immune diseases

              **LONG-TERM EFFECTS: GI bleeding, infection risk, inability

                   for wounds to heal, irregular heartbeat, muscle cramps, behavioral

                   changes (EX: Prednisolone, Dexamethasone)

     H. Non-Steroidal Anti-inflammatory Drugs (NSAIDs) -less side affects 

           1. Phenylbutazone- original NSAID, used more in horses 

                **CAREFUL: dogs metabolize drug quickly, difficult to keep in system

                                          cats metabolize drug slowly, can become TOXIC 

          2. Carprofen- approved to use in dogs with arthritis (relieve pain/inflammation)