Lecture 12: Adjunct Drugs & Interactions (Exam 2) Flashcards
What are adjunct drugs to anesthesia & analgesia
Drugs that may or may not be common for clinical use but play a supportive role by the benefit that they provide the px
Describe balanced anesthesia
Simultaneous use of multiple drugs & tech to produce anesthesia
Describe multimodal analgesia
Using 2 or more different drugs or techniques to manage pain
What can be given to limit nausea & vomiting? What can it lead to?
- Antiemetics
- May lead to aspiration pneumonia
Describe maropitant (cerenia)
- Neurokinin-1 receptor antagonist
- Often used for motion sickness
What are the perioperative period benefits of maropitant
- Reduced incidence of vomiting from certain premed drugs
- Improvement in recovery quality & a faster return to feeding
- Potential MAC lower effects when admin as a CRI
What can happen if maropitant is given IV instead of SQ
- Faster onset
- Potential for hypotension
T/F: Maropitant prevents gastoesophageal reflux (GER)
False it does not
Who is generic & other formulation of maropitant FDA approved for
Use in dogs older than 4 M for motion sickness & acute vomiting
What is a common side effect of generic & other formulations of maropitant
Excessive drooling
Describe vomiting
- Forceful ejection of stomach & upper intestinal contents
- Can contain yellow bile or partially digested dog food
- Usually smells sour & involves heaving
Describe regurgitation
- Mild ejection of undigested food from the esophagus
- Does not involve abdominal heaving
- Tends to happen just after eating
Describe Ondansetron
- 5HT3 receptor antagonist
- Antiemetic that works @ the level of the vomiting center in the brain particularly useful for prevention of vomiting due to chemotherapy drugs or from anesthetic drugs that induce vomiting
- Ava in tablet form, oral solution, & injectable solution
- Less effective than maropitant in prevention of vomiting but oral admin can reduce incidence of nausea
Describe metoclopramide
- Block dopamine D2 receptors in chemoreceptor trigger zone & also blocks serotonin receptors to contribute to antiemetic effects
- Prokinetic effects reduce the amount of gastric fluid via increasing the rate of gastric emptying
- Increase lower esophageal sphincter tone
- May increase CNS depressant effects of anesthetic drugs
- Do not give if there is a GI obstruction suspected, hx of seizure, or pheochromocytoma is present
Describe histamine receptor antagonists
- Given to decrease acid production in the stomach
- H2 antagonists such as famotidine or ranitidine
When is diphenhydramine commonly given
Prior to mast cell tumor removal to competitively counter the effects of histamine (H1 antagonist)
Describe proton pump inhibitors
- Decrease gastric acid production by irreversibly blocking H+/K+ATPase
- Omeprazole & pantoprazole are most commonly used
- Long-acting drugs
What is the effect of NSAIDs on MAC
They have a sparing effect
When should NSAIDs be given
Give them postoperatively in case of hypovolemia or hypotension occurs during anesthetic period, leading to decreased renal blood flow
Describe glucocorticoids
- Never give concurrently w/ NSAIDs
- Used for anti-inflammatory, analgesic, immunosuppressive, & for physiologic support of Addisonian px
What antibiotics are used w/ anesthesia
- Cefazolin
- Unasyn (ampicillin/sulbactam)
- Gentamicin
- K-pen
- PPG
- Naxcel
How should cefazolin be given
In an IV slowly over 5 min
How should unasyn be given
IV slowly over 15 - 30 min
How should gentamicin be given
IV & administered slowly
How should K-pen be given
IV slowly
How should PPG not be given
IV
What animals is Naxcel used on
Food animals
Describe aminocaproic acid
- Anti-fibrinolytic agent
- Can be given to greyhounds to decrease postop bleeding by enhancing clot formation & increasing clot strength
- Oral or injectable formulas
- Give slowly IV after diluting in saline to prevent CV effects
What breed of dogs have a higher than norm rates of bleeding 24 - 48 H post op
Greyhounds
Describe Desmopressin
- Hormone given to temporarily increase von willebrand factor in dogs w/ a deficiency prior to surgery
- Promotes vWf secretion from endothelium storage sites
- Desmopressin is a synthetic replacement for vasopressin (a hormone that reduces urine production)
- A nasal spray typically
- Expensive
Describe Dantrolene
Peripherally acting muscle relaxant (works on skeletal muscle but can cause cardiac depression)
What is the MOA of Dantrolene
Ryanodine receptor antagonism -> reducing Ca2+ release from the SR into the cytoplasm
What is the indication of Dantrolene
For the tx & prevention of malignant hyperthemia & exertional rhabdomyolysis
Describe Doxapram
- CNS stimulant
- Arousal from sedation/anesthesia (controversial), stimulation of respiration in neonates, & the assessment of laryngeal function (dogs & horses)
What is the MOA of Doxapram
Likely due to both central & peripheral effects -> increased activity of the respiratory nuclei of the medulla (significant increase in minute ventilation through an increase in RR & tidal vol)
What can an increased dosage of Doxapram lead to
Convulsions due to cortical stimulation
Describe Guaifenesin (aka GG)
- Central acting muscle relaxant w/ sedative properties
- Likely works both in the brain & the spinal cord
- Co-administered w/ IV anesthetics in horses & ruminants to induce & maintain anesthesia
- No known analgesic properties
- Wide therapeutic margin w/ mild cardiorespiratory effects
Define lidocaines
An amide local anesthetic drug used to provide locoregional analgesia & also used systemically to treat ventricular arrhythmias
What effects does lidocaine have
- MAC sparing
- Anti-inflammatory
- Analgesic
- Prokinetic effects on the GI tract by stimulating intestinal motility
T/F: Lidocaine is not typically used in cats as a CRI due to potential toxicity
True
What does Lidocaine CRI treat in equine
- Ileus - stimulates intestinal muscle contraction (in vitro) + analgesia
- Impactions
- Duodenitis-jejunitis
- Inflammation (preserves microvascular integrity, prevents neutrophil migration, & inhibits cytokine production)
How long is lidocaine CRI given
For 1 to 3 D
What are the signs of lidocaine toxicity
- Muscle fasicuulations
- Weaknes
- Recumbency
When lidocaine is discontinued imm signs will quickly disappear
Describe a ketamine CRI
- NMDA receptor antagonist given as an intraoperative CRI binds @ the CNS receptors & prevents “wind up”
- Best used to manage neuropathic types of pain (esp if the pain is chronic & the px has not responded well to other analgesic options)
- Always combine w/ an opioid &/or lidocaine infusion
What opioids can be used for an opioid CRI
- Fentanyl
- Remifentanil
- Morphine
- Hydromorphone
- Butorphanol
- Buprenorphine
How is an opioid CRI done
- Typically a loading dose is given first followed by the CRI
- The drug is diluted in fluids & admin in a syringe pump or as part of the IVF given during during anesthesia (recommend an IV fluid pump over a free drip rate)
T/F: Morphine-lidocaine-ketamine (MLK) lowers the MAC of Isoflurane by at 48%
True
How is a MLK made
- In a 500ml bag of fluid @ 5ml/kg/hr add 24 mg of Morphine, 60 mg of ketamine (100mg/mL), & 300mg of Lidocaine (20mg/mL)
What will inhibit concious perception
- General anesthetics
- Opioids
- Alpha 2 agonist
What inhibits spinal cord sensitization
- Opioids
- NSAIDs
- NMDA antagonists
- Alpha 2 agonists
- Local anesthetics
What inhibits transmission along the peripheral nerves
*local anesthetics
* Alpha 2 agonists
What inhibits nociceptor/painful stimulus?
- Local anesthetics
- Opioids
- NSAIDs
Calculate the following:
https://ivapm.org/professionals/cri-calculator/
What are some additional analgesic adjuncts
- Gabapentin
- Pregabalin
- Tramadol
- Amantadine
- Amitriptyline
- Acetaminophen
- Localregional anesthesia
- Dexmedetomidine CRI
What pharmaceutical interactions can occur in vitro (syringe or vial)
- Drug precipitate
- Toxic product
- Inactivate one of the drugs
- Acid-base interactions
- Chemical incompatibilities
What PK & PD can be affected by in vivo drug interactions
- Absorption
- ABCB 1
- Hepatic clearance
- drug protein binding
What is the MDR1 gene mutation (ABCB1)
Some herding-breed dogs have a single mutation in a gene for a protein (p-glycoprotein) that drastically affects absorption, distribution, metabolism, & excretion of drugs
What is the P-glycoprotein
- An important part of the blood-brain barrier
- Protects the body from toxic accumulations of substances
What drugs are affected by the MRD1 gene
- butorphanol
- Acepromazine
Why does knowing if a dog has a MDR1 gene mutation matter
- Dog w/ this mutation may have more serious side effects such as CNS &/or respiratory depression from certain anesthetic drugs
- Recovery may take longer & px may still appear sedated long after drugs should have norm worn off
- Generally recommend reducing the norm dose by 25-50% in dogs that are homozygous for the mutation
What is incompatible w/ diazepam
- Precipitation will occur w/ aques solutions & significant absorption into soft plastic w/in 24 H
- Heparin flush
What drugs are incompatible w/ alkaline solutions
- Epinephrine
- Dobutamine
- Dopamine
What is incompatible w/ phenylbutazone
Aqueous solutions
What should not be mixed w/ sodium bicarbonate
W/ solutions that contain calcium b/c precipitation may occur
Define addition
Simple additivity of fractional doses of two or more drugs
Define synergism
Response to fractional doses is greater than the response to the sum of the fractional doses
Define potentiation
Enhancement of action of one drug by a second drug that has no detectable action of its own
Define antagonism
Opposing action of one drug toward another
Define competitive antagonism
drugs that compete for the same receptor site
Define noncompetitive antagonism
Drugs act via different receptors
