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Questions and Answers
What is the primary goal of analgesic therapy?
What is the primary goal of analgesic therapy?
Which type of pain is characterized by a sudden onset and typically resolves in a short time frame?
Which type of pain is characterized by a sudden onset and typically resolves in a short time frame?
Which of the following classes of drugs includes both opioids and non-opioids?
Which of the following classes of drugs includes both opioids and non-opioids?
Which compound serves as a cough suppressant among the active ingredients in opium?
Which compound serves as a cough suppressant among the active ingredients in opium?
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Which type of pain is typically associated with musculoskeletal damage?
Which type of pain is typically associated with musculoskeletal damage?
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What distinguishes opioids from opiates?
What distinguishes opioids from opiates?
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Which term accurately describes drugs derived from opium that have narcotic properties?
Which term accurately describes drugs derived from opium that have narcotic properties?
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Which class of drugs is commonly used for managing neuropathic pain?
Which class of drugs is commonly used for managing neuropathic pain?
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What is the role of the Blood-Brain Barrier (BBB)?
What is the role of the Blood-Brain Barrier (BBB)?
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Which of the following characteristics enable drugs to cross the BBB?
Which of the following characteristics enable drugs to cross the BBB?
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Which targets are primarily affected by neuroactive drugs?
Which targets are primarily affected by neuroactive drugs?
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What happens to the permeability of the BBB during inflammation?
What happens to the permeability of the BBB during inflammation?
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Which process occurs after neurotransmitter release at the synapse?
Which process occurs after neurotransmitter release at the synapse?
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What is the primary function of neuroactive drugs concerning ion channels?
What is the primary function of neuroactive drugs concerning ion channels?
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What defines the synaptic process involving receptor-induced changes?
What defines the synaptic process involving receptor-induced changes?
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Which of the following accurately describes analgesics?
Which of the following accurately describes analgesics?
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What is the primary role of CNS drugs?
What is the primary role of CNS drugs?
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What is a characteristic of controlled drugs?
What is a characteristic of controlled drugs?
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Which type of drug suppresses the transmission of neural signals?
Which type of drug suppresses the transmission of neural signals?
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What distinguishes agonists from antagonists in drug action?
What distinguishes agonists from antagonists in drug action?
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Which is a non-opioid analgesic agent?
Which is a non-opioid analgesic agent?
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What is the average success rate of Phase III candidate drugs in CNS applications?
What is the average success rate of Phase III candidate drugs in CNS applications?
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What is one of the adversities associated with opioid use?
What is one of the adversities associated with opioid use?
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Which mechanism describes how some drugs can alter synaptic transmission without binding to receptors?
Which mechanism describes how some drugs can alter synaptic transmission without binding to receptors?
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What is a key consequence of drug actions in the CNS?
What is a key consequence of drug actions in the CNS?
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What are NMDA-receptor antagonists primarily used for?
What are NMDA-receptor antagonists primarily used for?
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What is the primary mechanism of action of opioids in the body?
What is the primary mechanism of action of opioids in the body?
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Which opioid is known to have the highest potency among the common agonists listed?
Which opioid is known to have the highest potency among the common agonists listed?
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What is a common side effect associated with mu-receptor activation?
What is a common side effect associated with mu-receptor activation?
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Which of the following receptors is primarily involved in spinal and supraspinal analgesia?
Which of the following receptors is primarily involved in spinal and supraspinal analgesia?
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What is a unique characteristic of opioids in terms of safety for animals?
What is a unique characteristic of opioids in terms of safety for animals?
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Which of the following opioids is classified as a partial agonist?
Which of the following opioids is classified as a partial agonist?
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What is the elimination half-life of opioids typically observed in dogs?
What is the elimination half-life of opioids typically observed in dogs?
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What effect can opioids have in cats that differs from dogs?
What effect can opioids have in cats that differs from dogs?
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Which medication is NOT classified as an opioid agonist?
Which medication is NOT classified as an opioid agonist?
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What is the main use of tramadol in veterinary medicine?
What is the main use of tramadol in veterinary medicine?
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How do NMDA receptor antagonists function in pain management?
How do NMDA receptor antagonists function in pain management?
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Acetaminophen is considered which type of analgesic?
Acetaminophen is considered which type of analgesic?
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What is an important consideration when administering opioids to cats?
What is an important consideration when administering opioids to cats?
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What can excessive binding of opioids to mu receptors lead to?
What can excessive binding of opioids to mu receptors lead to?
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Study Notes
CNS Pharmacology
- CNS Pharmacology focuses on how drugs modify brain activity to address pathologies.
- Neuropharmacology delves into how drugs interact with neurons at cellular and molecular levels.
- PsychoPharmacology studies how drugs alter behavior, perception, and thoughts.
CNS Drug Development
- Recent decades have witnessed significant advancements in CNS pharmacology.
- However, drug development efforts in neuropsychiatric areas are facing challenges primarily due to a low rate of treatment success.
- Compared to other drugs, CNS drugs have a lower clinical use rate, longer regulatory approval timeframe, and less successful phase II/III trials.
CNS Drugs: Therapeutic Importance and Action
- CNS drugs are used to address various conditions related to brain stimulation or depression.
- These drugs can relieve pain and fever, suppress movement disorders or seizures, induce sleep or arousal, reduce appetite, inhibit motion sickness, and treat anxiety, mania, and depression.
- Prescription drugs require veterinary supervision due to their potential dangers or difficult administration.
- Controlled drugs have a high potential for abuse or dependence and are categorized into schedules based on their abuse potential.
Drug Action in the CNS
- CNS drugs mimic neurotransmitters, by speeding up or slowing down the process of transferring electro-chemical messages between neurons in the brain and spinal cord.
- These drugs act on specific receptors that modulate synaptic transmission.
- Some agents, such as alcohol and anesthetics, have non-receptor-mediated actions that alter synaptic activity.
Effects of CNS Drugs
- CNS drugs can induce various effects, including analgesia, tranquilization (sedation), anticonvulsant, antiemetic, anxiolytic, sedative, hypnotic, and general anesthetic effects.
- They can also cause behavioral changes by stimulating or depressing the CNS.
Agonists and Antagonists
- Agonists: Bind to and stimulate target CNS tissues.
- Antagonists: Bind to target tissues but do not stimulate them.
Sites for Drug Action
- Drug action in the CNS can occur at different sites, including:
- Action potential generation in presynaptic fibers.
- Synthesis of neurotransmitters.
- Storage of neurotransmitters.
- Metabolism of neurotransmitters.
- Release of neurotransmitters.
- Reuptake into presynaptic neurons or glial cells.
- Degradation of neurotransmitters.
- Receptor binding for neurotransmitters.
- Receptor-induced changes in ion conductance.
- Retrograde signaling.
Targets for Drug Action
- Neuroactive drugs primarily target ion channels, receptors, enzymes, and transport proteins.
- These targets often exist in multiple molecular isoforms, leading to subtle differences in function and pharmacology.
- Secondary responses to drug-target interactions can be important, contributing to delayed efficacy of antidepressants and tolerance/dependence with opioids.
The Blood-Brain Barrier (BBB)
- The BBB is a highly selective barrier separating the brain tissue from the blood circulation.
- Its primary function is to protect the CNS from toxins, pathogens, and even neurotransmitters like glutamate.
- It consists of a continuous layer of endothelial cells linked by tight junctions and surrounded by astrocytes.
Drugs and the BBB
- Drugs must cross the BBB to reach neurons in the brain.
- Factors influencing drug crossing:
- Small molecular size.
- Lipid solubility (lipophilicity).
- Poor protein binding.
- Non-ionized at cerebrospinal fluid (CSF) pH.
- Drug transfer can occur via diffusion or carrier-mediated mechanisms.
- The BBB permeability can increase during inflammation or at tumor sites.
- The BBB is poorly developed in neonates, making the neonatal brain susceptible to chemicals.
Analgesics
- Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage.
- Analgesic drugs inhibit pain processing at different levels.
- The goal of analgesic therapy is to reduce transduction, transmission, modulation, and perception of pain.
Classes of Pain
- Acute pain: Sudden onset, resolves in 1-3 days. Initiated by traumatic insult, well-controlled with analgesics.
- Chronic pain: Slow onset, persists for weeks/months. Altered homeostasis, long-term distress. Requires a combination of potent analgesics.
- Visceral pain: Originates in abdominal or thoracic cavities.
- Somatic pain: Arises from musculoskeletal damage.
- Neuropathic pain: Damage affecting the somatosensory nervous system.
Pharmacological Intervention of Pain Processing
- Analgesic drugs can intervene at different stages of pain processing.
- Tricyclic antidepressants, cholinesterase inhibitors, anticonvulsants, and phenothiazines can interfere with the modulation of pain signals in the central nervous system.
- Opioids and non-opioids (NSAIDs) are major classes of drugs that directly intervene with pain transduction and transmission at the peripheral and spinal cord level.
Opioids
- Opioids are derived from the poppy plant and act as agonists, partial agonists, or mixed agonist-antagonists.
- Opium is an extract from the white milky sap of poppy bulbs, containing morphine and codeine.
- Opiates are natural or semi-synthetic narcotic drugs with narcotic properties, including opium, morphine, codeine, and heroin.
- Opioids are fully synthetic or semi-synthetic narcotic drugs that mimic natural opiates.
- Endogenous opioid neuropeptides (endorphins, enkephalins, dynorphins) are released by neuroendocrine cells to activate opioid receptors.
Opioids: Classification and Uses
- Agonists: Morphine, hydromorphone, oxymorphone, fentanyl, tramadol.
- Partial agonists: Butorphanol, buprenorphine, nalbuphine.
- Antagonists: Naloxone, naltrexone.
- Opioids are controlled substances, except for antagonists and some partial agonists.
- They are administered via various routes, including IV, IM, SC, oral, rectal, transdermal, subarachnoid, and epidural.
- They are metabolized in the liver and excreted in the urine.
- Cats have a prolonged half-life for most opioids due to metabolic deficiencies.
- Opioids have a wide margin of safety.
Opioids: Pharmacological Effects
- Opioids can produce analgesia and sedation.
- They can induce anesthesia when combined with other drugs.
- Their effects vary between species.
- Dogs: Sedation, narcosis.
- Cats, horses, ruminants: CNS stimulation, bizarre behavior, dysphoria.
Opioids: Mechanism of Action (MOA)
- Opioids mimic endogenous opioid peptides by binding to opioid receptors (mu, kappa, and delta) in the brain and spinal cord, inhibiting neurotransmission and endocrine secretion.
- Each type of opioid has a distinct action at each receptor.
- Opioid receptors are located throughout the body, including the brain, spinal cord, peripheral neurons, digestive tract, and urinary tract.
Opioid Receptors
- All opioid receptors are G-protein coupled receptors mediating inhibition of neurotransmission and endocrine secretion.
- They are found in various tissues and cells.
- µ-receptors: Present in the brain and spinal cord. Responsible for spinal and supraspinal analgesia, euphoria, mild sedation, miosis, respiratory depression, chemical dependence, inhibition of acetylcholine and dopamine release, and decreased GI motility.
- κ-receptors: Found in the cerebral cortex, spinal cord, and other brain regions. Responsible for spinal and supraspinal analgesia, sedation, dysphoria, diuresis, and miosis.
- Δ-receptors: Located in the limbic system, cerebral cortex, and spinal cord. Responsible for spinal and supraspinal analgesia, inhibition of dopamine release, and cardiovascular depression.
Non-Opioid Analgesic Drugs
- Non-steroid anti-inflammatory drugs (NSAIDs) are used to reduce swelling, stiffness, and joint pain caused by inflammation.
- They inhibit the pro-inflammatory enzyme cyclooxygenase (COX).
- Nonselective NSAIDs: Inhibit both COX1 and COX2.
- Selective NSAIDs: Inhibit COX2.
- Common NSAIDs examples: Acetaminophen (Paracetamol, Tylenol), Ibuprofen, and Aspirin.
- Veterinary NSAIDs:
- Carprofen: Dogs, cats, reptiles, and birds. Rare side effects include kidney and liver damage, GI problems, and drug-drug interactions.
- Deracoxib: Dogs only, post-surgery.
- Firocoxib: Dogs, horses, osteoarthritis, and surgery.
- Meloxicam: Dogs and cats, osteoarthritis.
NMDA Receptor Antagonists as Analgesics
- N-methyl-D-aspartate (NMDA) Receptor: A glutamate receptor and calcium ion channel.
- Ligands: Glutamate and glycine.
- NMDA receptors play a role in learning and memory.
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NMDA Receptor Antagonists:
- Amantadine: Anti-dyskinetic, used for acute and chronic pain in dogs and cats.
- Ketamine: Anesthetic, used in hospitals.
- Gabapentin: GABA analogue, anticonvulsant, used for neuropathic pain and cancer-related pain.
- Amitriptyline: Antidepressant, used for arthritis, neuropathic pain, and chronic pain.
- Lidocaine patch: Local anesthetic, used for veterinary pain management.
- Methadone: Analgesic and pre-anesthetic in dogs and cats.
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Description
This quiz covers key concepts in CNS pharmacology, including how drugs modify brain activity and their therapeutic importance. Explore the challenges in CNS drug development and the diverse actions of these medications in treating various brain-related conditions.
