fundamentals of pharmacology for veterinary technicians

Fundamentals of Pharmacology for Veterinary Technicians Chapter 7

Figure 7-1


Figure 7-2


Figure 7-3


Figure 7-4


Figure 7-6


Figure 7-7


Figure 7-8


Figure 7-9


TABLE 7-1 Barbiturate Classifications (by duration of action)

Classification Duration of action Examples

Long-acting 6–8 hours phenobarbital

Short-acting 1 hour pentobarbital

Ultrashort-acting 10–15 minutes thiopentalmethohexital

Table 7-1


Table 7-2

TABLE 7-2 Properities of Sedatives, Tranquilizers, and Anti-anxiety Drugs

Phenothiazines BenzodiazepinesAlpha-2 agonists

Classification:

Sedation XX

Anti-anxiety X X

Antiemetic X

AnalgesicX

(someshort duration)

Antiarrhythmic X

Antihistimine effect X

Peripheral vasodilation X


Table 7-3

TABLE 7-3 Types of Local Anesthesia

Type Description Benefit UseDrug example

Infiltration anesthesia Small amounts of Because small amounts • Wound suturing •lidocaine

anesthetic solution are of anesthetic are used, • Wound debriding •mepivacaine

injected into the tissue there is reduced • Skin biopsies •tetracaine

surrounding the site to danger of systemic •bupivacaine

be worked on (surgical side effectssite, wound repair site, etc.)

Topical anesthesia Anesthetic agent is Systemic absorption is • Eye examinations •tetracaine

applied directly onto the limited from these sites • Minor skin irritation •proparacaine

surface of the skin or • Catheter passing (gel eye; also used to aid in is applied to the diagnostic procedures catheter tip)and intubation in cats • Larynx is sprayed to

liquid applied to prevent spasming during intubation in cats

Nerve block anesthesia Anesthetic solution is Localization of pain relief • Helps locate areas of •lidocaine

injected along the course Ability to determine the injury •mepivacaine

of a nerve so that the source of pain • Provides local •bupivacaine


Table 7-4

TABLE 7-4 Methods of Administering Anesthetics by Inhalation

Method Description Description/Example

Open-drop Liquid anesthetic is dropped • This method is not onto a cloth and extended used anymore because over the animal’s nose and there is lack of control mouth over the amount of anesthetic

delivered, and there is no respiratoryassistance. It is also not currently usedbecause these agents (such as ether)are flammable.

Semi-closed Anesthetic is provided • Need to use a through a mask connected rapid-acting anesthetic to a reservior (usually a gas like halothane oranesthetic machine) isoflurane and related

anesthetics• Provides greater control

of anesthesia delivered to the patient as

compared to theopen-drop method

• Exhaled gases still leakinto the environment

Closed Anesthetic is delivered by• Animal is intubated withanesthesia machine after the an endotracheal tubeliquid has vaporized to the and inhalant anesthetic inhalant (gas) form is delivered directly to

the respiratory system• Examples include isoflurance and

related anesthetics; halothane


Table 7-5

TABLE 7-5 Effects of Cholinergic Drugs

Body Tissue Effect of Cholinergic Drugs

Cardiovascular Decreases heart rate, causes vasodilation (lowers blood pressure),and slows conduction of the AV node

Lung (bronchi) Stimulates bronchial smooth muscle contraction and increasesbronchial secretions

Gastrointestinal Increases motility of the smooth muscles of the stomach,increases peristalsis, and relaxes sphincter muscles.

Urinary Contracts urinary bladder muscles, relaxes sphincter muscles ofthe urinary bladder, and stimulates urination

Ocular Causes miosis (pupillary constriction)

Skeletal muscle Maintains muscle strength and tone

Glandular Increases salivation, perspiration, and tear production


Table 7-6

TABLE 7-6 Effects of Anticholinergic Drugs

Body Tissue Effect of Anticholinergic Drugs

Cardiovascular Increases heart rate

Lung (bronchi) Dilates bronchi and decreases bronchial secretions

Gastrointestinal Relaxes smooth muscle tone of the gastrointestinal tract,decreases gastrointestinal motility and peristalsis, and de-creasesgastric and intestinal secretions

Urinary Relaxes urinary bladder muscles, increases constriction of theinternal sphincter muscle of the urinary bladder, and causes urineretention

Ocular Causes mydriasis (pupillary dilation) and paralyzes the ciliarymuscle

CNS/Muscular system Decreases muscle rigidity and can cause drowsiness anddisorientation

Glandular Decreases salivation, perspiration, and tear production


Table 7-7

TABLE 7-7 Effects of Adrenergics and Adrenergic Blocking Agents

Adrenergic Blocking Receptor Adrenergic Drug Effect Drug Effect

alpha-1 Increases force of heart contraction, Vasodilation and miosisincreases blood pressure, and causes mydriasis

alpha-2 Inhibits release of norepinephrine andNone dilates blood vessels, producing hypotension

beta-1 Increases heart rate and force of heart Decreases heart ratecontraction

beta-2 Dilates bronchioles and relaxes Constricts bronchiolesgastrointestinal tract


Table 7-8

TABLE 7-8 Types of Drugs Covered in this Chapter

Drug Category Examples

Anticonvulsants • phenobarbital• pentobarbital• primidone• diazepam• clorazepate• potassium bromide• valproic acid• phenytoin

Tranquilizers/sedatives/anti-anxiety • phenothiazine derivatives:acepromazine, chlorpromazine, prochlorperazine/

isopropamide, promazine• benzodiazepines: diazepam,

zolazepam, midazolam,clonazepam

• alpha-2-agonists: xylazine,detomidine, medetomidine

Narcotic analgesics • opium• morphine• meperidine• hydromorphone• butorphanol• hydrocodone• fentanyl• etorphine• buprenorphine• pentazocine• diphenoxylate• apomorphine• loperamide• methadone• codeine

Opioid antagonists • naloxone• naltrexone

Neuroleptanalgesics • xylazine & butorphanol• acepromazine & morphine

Local anesthetics • lidocaine• proparacaine• mepivacaine• tetracaine• bupivacaine

General anesthetics (injectable) • barbiturates: phenobarbital, pentobarbital, thiopental,

methohexital• dissociatives: ketamine, tiletamine• miscellaneous: guaifenesin,

propofol

Analgesic (inhalant) • nitrous oxide


Table 7-8 Continued

Analgesic (inhalant) • nitrous oxide

General anesthetic (inhalant) • halothane• isoflurane, enflurane, desflurane, sevoflurane

TABLE 7-8 Continued

Drug Category Examples

CNS stimulants • doxapram• methylxanthines

Euthanasia solutions • pentobarbital combinations

Cholinergics • bethanechol• metoclopramide• pilocarpine• edrophonium• neostigmine• demecarium• organophosphates

Anticholinergics • atropine• glycopyrrolate• aminopentamide• propantheline

Adrenergics • epinephrine• norepinephrine• isoproterenol• dopamine• dobutamine• phenylpropanolamine• isoetharine• albuterol• terbutaline• ephedrine• xylazine

Adrenergic blocking agents • alpha-blockers: phenoxybenzamine, prazosin, yohimbine

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