Types of Drugs Flashcards
Local Anesthetics
Prototype
Procaine
Local Anesthetics
Mechanism of Action
- Inhibits sodium channels
2. Channel is open less often
Local Anesthetics
Clinical Uses
- Local anesthesia
2. Antiarrhythmic
Local Anesthetics
Adverse Effects & Toxicity
- Lower doses = CNS excitement = seizures
- Very high doses = CNS depression
a. Respiratory collapse
b. Cardiovascular depression
Local Anesthetics
Contraindications
- Do NOT use benzocaine or tetracaine in cats
Local Anesthetics
Chemistry
- Weak bases
- Two categories
a. Esters
b. Amides
Local Anesthetics
Metabolism
- Esters = plasma = shorter duration
2. Amides = hepatic = longer duration
Major Tranquilizers
Prototype
Acetylpromazine
Major Tranquilizers
Chemistry
Two categories
- Phenothiazines = Acetylpromazine
- Butyrophenone = Droperidol
Major Tranquilizers
Mechanism of Action
Antagonist Actions
- D, NE & S = monoamines
- Muscarinic cholinergic Ach receptors
- Alpha-adrenergic receptors = sympathetic NS
- Histamine receptors
Major Tranquilizers
Clinical Uses
- Sedation
- Muscle relaxation = less than barbiturates
- Hypnosis = catalepsy
- Anticholinergic activity = less atropine needed
Major Tranquilizers
Metabolism
- Highly protein bound
2. Hepatic metabolism
Major Tranquilizers
Adverse Effects & Toxicity
- Hypotension = use norepinephrine!
- Catalepsy
- Seizures = accidental IV injection
Major Tranquilizers
Contraindications
- Patients with epilepsy
2. Strychnine poisoning
Minor Tranquilizers
Prototype
Diazepam
Minor Tranquilizers
Chemistry
Four groupings
- Benzodiazepines = diazepam
- Chloral hydrate
- Alipathic alcohols
- Barbiturates
Minor Tranquilizers
Mechanism of Action
A. Interacts with GABA(A) receptor
B. Enhances GABA inhibition
C. Chloride channels = increases opening frequency
Minor Tranquilizers
Clinical Uses
- Restraint & calming
- Anticonvulsant = more than MTs
- Pre-anesthetic drug
a. More skeletal muscle relaxation than MTs
b. Blocks excitatory effects - Does NOT induce anesthesia
Minor Tranquilizers
Metabolism
Metabolites are active!
Minor Tranquilizers
Adverse Effects & Toxicity
- Ataxia
- Excitation in cats
- Apnea when given IV
- Respiratory depression = more than MTs
- Risk for withdrawal = opposite of MTs
- Hypothermia
Minor Tranquilizers
Contraindications
None discussed
Alcohols
Prototype
Ethanol
Alcohols
Chemistry
Tertiary alcohols produce the most sedation
Alcohols
Mechanism of Action
Ethanol
Potentiates GABA receptor activity
Similar to inhalant anesthetics
Alcohols
Clinical Uses
- Sedative
- Block methanol & ethylene glycol toxicity
- Permanent nerve block
Alcohols
Metabolism
- Rapid absorption
2. Zero-order kinetics = loading dose needed
Alcohols
Adverse Effects & Toxicity
- Acidosis = acidic metabolites
- Hypothermia
- CNS & respiratory depression
Alcohols
Contraindications
None discussed
Stimulants
Prototype
Variety of compounds
Stimulants
Chemistry
- Methylxanthines = theobromine
- Doxapram
- Cocaine
- Strychnine
Stimulants
Mechanism of Action
Various
- Theophylline & theobromine = inc cortex activity
- Doxopram = inc. medulla activity
- Strychnine = inhibits Renshaw cells
- Cocaine = inhibits reuptake of monoamines
Stimulants
Clinical Uses
- Toxicity
2. Stimulate respiration = doxopram
Anticonvulsants
Prototype
Acute = diazepam Prevention = phenobarbital
Anticonvulsants
Mechanism of Action
Two actions
- Block sodium channels
- Increase GABA activity = inhibitory activity
Anticonvulsants
Clinical Uses
Um… to stop seizures
Anticonvulsants
Metabolism
Not discussed
Anticonvulsants
Adverse Effects & Toxicity
- Cessation of drug therapy may be lethal to the patient!
Anticonvulsants
Contraindications
Not all anticonvulsants are good in all situations
Barbiturates
Prototype
- Phenobarbital
- Pentobarbital
- Thiopental
Barbiturates
Chemistry
- Weak acids
Barbiturates
Mechanism of Action
Three fold mechanism:
- Enhance GABAergic activity
- Inhibit NT release
- Inhibit calcium uptake
Barbiturates
Clinical Uses
Injectable anesthesia!
NO no no analgesia!
Barbiturates
Metabolism
- Lipid solubility determines duration of action
- High protein binding
- Redistribution is important
Barbiturates
Adverse Effects & Toxicity
- Inc GI motility
- Dec uterine contractions
- Inc secretions
- Laryngeal spasms
- Cardiac depression = dec. BP and CO
- Inhibits respiratory drives
a. Chemogenic drive = CO2
b. Hypoxic drive = O2 - Tissue irritation = IV ok
Barbiturates
Contraindications
- High plasma protein binding
= can displace other drugs
Dissociatives
Prototype
Ketamine
Dissociatives
Chemistry
Very lipid soluble
Dissociatives
Mechanism of Action
- Inhibition of the NMDA receptors
2. Binds sigma-type opioid receptors
Dissociatives
Clinical Uses
- Sedative
a. Can be used alone in cats
b. Dogs & horses require a pre-medicatio sn - Anesthesia = but maintain muscle tone
- Catalepsy = dissociation from enviroment
Dissociatives
Metabolism
Hepatic
Dissociatives
Adverse Effects & Toxicity
1. Do NOT use in trauma situations = increase in intracranial pressure = Increase in BP = bleeding risk 2. 50% of dogs will have seizures w/o pre-med 3. Risk for emesis during emergence
Dissociatives
Contraindications
- Epilepsy
2. Head trauma or any trauma
Inhalant Anesthetics
Prototype
Methoxyflurane
Inhalant Anesthetics
Chemistry
A. Dose = partial pressure or volume precent
B. Lower MAC value = MORE potent
C. More lipid soluble = more potent
Inhalant Anesthetics
Mechanism of Action
Affects the function of 3 channels:
- GABA channels
- Glycine ion channels
- Inhibition of nicotinic cholinergic receptors
Inhalant Anesthetics
Clinical Uses
- CNS depression
2. Surgical anesthesia
Inhalant Anesthetics
Metabolism
- Tissue uptake
a. Highest blood flow = brain, GI, liver, kidneys
b. Greatest mass = skin, muscle
c. Body fat = high solubility but low blood flow - Metabolism
a. Risk in fluorinated anesthetics
b. More metabolism = more toxicity
c. May not be much metabolism - Elimination
a. Lungs
b. Skin & mucus membranes
c. Urine & milk
Inhalant Anesthetics
Adverse Effects & Toxicity
- CNS depression
- Increase in intracranial pressure
- Respiratory depression = acidosis
a. Blunts response to CO2 - Relaxation of cardiac & vascular muscle
a. Decreased CO & BP - Changes in blood flow
a. Increased cerebral
b. Decreased renal & hepatic
Opioid Analgesics
Prototype
Morphine
Opioid Analgesics
Chemistry
- Types
a. Agonist
b. Partial agonist
c. Competitive antagonist - Isomers
a. L-isomer = best anaLgesic
b. D-isomer = best antitussive
Opioid Analgesics
Mechanism of Action
- Opens potassium channels = hyperpolarization
- Closes calcium channels = less NT release
- Decreases cAMP = inhibitory
Opioid Analgesics
Clinical Uses
- Analgesia
- Antidiarrheal
- Antitussive = NOT through opioid receptors
- Sedation = dogs, rats, rabbits, primates
Opioid Analgesics
Metabolism
Bioavailability
- Codeine = 60%
a. Codeine can be metabolized to morphine! - Morphine = 25%
Opioid Analgesics
Adverse Effects & Toxicity
- Respiratory depression = Delta & Mu only
- Emesis
- Constipation
- Histamine release = esp. dogs
- Little to no cardiovascular effects!!!
Opioid Analgesics
Contraindications
Immune compromised animals