Lect 3 Flashcards
what are 2 families of adrenergic receptors?
and how are they further subdivided?
α adrenoceptor & β adrenoceptor
α adrenoceptor are subdivided into two groups:
α1 and α2 - these are further subdivided into:
α1A, α1B, α1C, α1D & α2A, α2B, α2C
what are the effects of stimulation of α1 adrenoceptor?
the site is at blood vessels
can be used for shock
Agonist does the following:
- increase peripheral resistance
- increase BP
- mydriasis
- increase closure of internal sphincter of bladder
what are the effects of stimulation of β1 adrenoceptor?
agonist does the following:
- tachycardia
- increase lipolysis
- increased myocardial contractility
- increase release of renin
can be used for heart failure
what are the effects of stimulation of β2 adrenoceptor?
agonist does the following:
- vasodilation
- slightly decrease peripheral resistance
- bronchodilation
- increased muscle and liver glycogenolysis
- increased release of glucagon
- relaxed uterine smooth muscle (can prevent preterm delivery)
what are DIRECT acting adrenergic agonist?
these drugs act directly on α or β receptors, producing effects similar to those that occur following stimulation of sympathetic nerves or release the hormone epinephrine from the adrenal medulla
there are two types of Direct acting adrenergic agonist:
catecholemines
noncatecholermines
epinephrine
Direct acting adrenergic agonist
catecholemines
α1, α2, β1, β2
used in intense asthma
anaphylactic shock, etc
dobutamine
Direct acting adrenergic agonist
catecholemines
β1
drug of choice to stimulate heart
dopamine
Direct acting adrenergic agonist
catecholemines
α1, β1
used to treat shock
Phenylephrine
Direct acting adrenergic agonist
Noncatecholemines
α1
causes intense vasoconstriction
Terbutaline
Direct acting adrenergic agonist
Noncatecholemines
β2
used as Bronchodilator (asthma)
Albuterol
Direct acting adrenergic agonist
Noncatecholemines
β2
used as Bronchodilator (asthma)
Salmeterol
Direct acting adrenergic agonist
Noncatecholemines
β2
long acting bronchodilator
what are INDIRECT acting adrenergic agonist?
they cause norepinephrine release from presynaptic terminals or inhibit the uptake of nor-epinephrine
Amphetamine
INDIRECT acting adrenergic agonist
has CNS stimulatory effects
used for Narcolepsy, ADHD, appetite control
Methylphenidate
same as Amphetamine
[INDIRECT acting adrenergic agonist
has CNS stimulatory effects
used for Narcolepsy, ADHD, appetite control]
what happens if a patient taking MAO-inhibitors eat lots of cheese?
- Tyraminine is oxidized by MAO (Manoamine oxidase)
- If patient taking MAO-inhibitors eat cheese, tyramine of cheese cannot be oxidized.
- Tyramine enters nerve terminal, and displaces store norepinephrine, thereby causing hypertensive crisis.
[patient can carry 25 mg tablets of chlorpromazine for emergency]
what are Adrenergic Antagonist?
these drugs bind to the adrenergic receptors and PREVENT their activation by endogenous epinephrine and norepinephrine
there are:
α-adrenergic blocking agents (non-selective & selective)
β - adrenergic blocking agents (non-selective & selective)
α & β blockers
MOA of non-selective α blockers (α1 and α2 blockers)?
these drugs block both α adrenergic receptors causing vasodilation and lowering blood pressure
Phenoxybenzamine
Adrenergic Antagonist
Non-selective α blockers (α1 and α2 blockers)
cause vasodilation & lower of blood pressure
used in tx of pheochromocytoma (tumor of adrenal medulla, which produces too much epinephrine), to treat hypertensive episodes
Doxazosin
Adrenergic Antagonist
Selective α1 blocker
used to tx Hypertension
this drug can cause orthostatic hypotension
Tamsulosin
Adrenergic Antagonist
Selective α1A blocker
relaxes smooth muscle in urinary bladder neck and prostate. thus improving urine flow in Benign Prostate Hyperplasia
Clonidine
Adrenergic Antagonist
α2 agonist (in blood vessel)
inhibits both sympathetic output from the brain and release of norepinephrine from nerve terminals.
Thus, they reduce blood pressure
USE - Hypertension
what is MOA of β-adrenergic blocking agents?
all the clinically available β-blockers are competitive antagonist.
non-selective β-blockers act at both β1 and β2 receptors, whereas cardioselective β-antagonists primarily block β1 receptors
Propranolol
β-adrenergic blocking agent (all tx Hypertension)
*this drug also treats angina, cardiac arrhythmias, myocardial infarction, congestive heart failure, hyperthyroidism, and glaucoma as well as serving in the prophylaxis of migraine HA.
CONTRAINDICATED for asthma patient
Sotalol
β-adrenergic blocking agent (all tx Hypertension)
*used for Ventricular arrhythmias and tachycardia
CONTRAINDICATED for asthma patient
Metoprolol
β1 - selective blocker
txs: Hypertension, Myocardial infarction, Angina pectoris
Atenolol
β1 - selective blocker
name drugs which are Mixed α and β blockers?
what do these drugs do?
Labetalol - α1, β1, β2 blockers (used for pre-eclampsia)
Carvedilol - α1, β1, β2 blockers
They decrease BP w/o reflec tachycardia. Used in tx of Hypertension
what are the cautions needed to take when a patient with type 1 diabetes is to be given Propranolol and why?
β blockade leads to decreased glycogenolysis and decreased glucagon secretion.
Thus, very careful monitoring of blood glucose is essential, bc pronounced hypoglycemia may occur after insulin injection. Also, reflex increase in heart rate that occurs in response to hypoglycemia is also blocked by β-blockers
what are risks of withdrawing β blockers? how can this be avoided?
treatment with β blockers when stopped abruptly risks severe precipitating cardiac arrhythmias.
the β blockers must be tapered off gradually for at least a few weeks. Long-term tx with β antagonist leads to up-regulation of the β receptor.
on suspension of therapy, the increased receptors can worsen angina or hypertension.
name excitatory and inhibitory neurotransmitters of brain?
excitatory neurotransmitters of CNS: acetylcholine, norepinephrine, dopamine, serotonin
inhibitory neurotransmitters of CNS: GABA, Glycine
what are 3 types of anti-Parkinson drugs?
- dopamine replacement therapy
- dopamine receptro agonist therapy - AD agonists can be sued bc although dopamine-releasing neurons have disappeared, the postsynaptic dopamine receptors are still present and functional. Administration of dopamine agonists to stimulate these receptors should therefore restore balance of inhibition and excitation in basal ganglia
- anticholinergic therapy - muscarinic antagonists used in Parkinson’s disease. They reduce Ach:Dopamine imbalance in striatum. Side effects of these drugs include dry mouth, constipation, urinary retention, confusion.
what is etiology of Parkinson’s disease?
loss of dopamine-containing neurons that project from substantia nigra to striatum where they inhibit cholinergic (Ach) neurons.
Normally, striatum is connected to the substantia nigra by neurons that secrete the inhibitory transmitter GABA at their termini in substantia nigra.
In turn, substantia nigra sends neurons back to the striatum, secreting transmitter dopamine at their termini. This mutual inhibitory pathway normally maintains a balance. Destruction of cells of substantia nigra results in overproduction of Acetylcholine which triggers a chain of abnormal signaling, resulting in loss of control of muscle movt.
Levodopa
- dopamine replacement therapy
metabolic precursor of dopamine
decarboxylated to dopamine in brain. DA does not cross blood-brain barrier
Carbidopa
- dopamine replacement therapy
diminishes decarboxylation of Levodopa (L-dopa) in peripheral tissues thereby prevents its peripheral biotransformation
Sinemet
- dopamine replacement therapy
Combination of Levodopa and Carbidopa
Selegiline
- dopamine replacement therapy
(also known as deprenyl)
inhibitor of monoamine oxidase-B (MOA-B), the enzyme that metabolizes dopamine in CNS
Amantidine
- dopamine replacement therapy
antiviral drug effective in Tx of influenza.
Also, enhances synthesis, release, or reuptake of dopamine from surviving neurons.
what two drugs are used in dopamine receptor agonist therapy?
Bromocriptine (powerful dopamine-receptro agonist)
Ropinirole
etiology of Alzheimer Disease (AD)?
- formation of Beta-amyloid plaque
- neurofibruatory tangles
decrease in choline acetyltransferase (that catalyzes the transfer of acetyl group of acetyl CoA to choline, forming acetylcholine) and other markers of cholinergic neuron activity.
eventually, cholinergic neurons die or are destroyed.
Tx focused on increasing amount of acetylcholine in synapse by inhibiting the breakdown of acteylcholine.
The most recent drug is an antagonist of N-methyl-D-asparate (NMDA) receptor (Glutamate receptor). Overstimulation of these receptors may be a mechanism of neurodegenerative process in AD.
Donezepil
anti-alzhemier drugs
cholinesterase inhibitor
memantine
anti-alzhemier drugs
NMDA antagonist
*[antagonist of N-methyl-D-asparate (NMDA) receptor (Glutamate receptor). Overstimulation of these receptors may be a mechanism of neurodegenerative process in AD]
appears to slow the progression of AD (slows the rate of memory loss)
what are Anxiolytic and Hypnotic drugs?
what are the 3 types?
used for tx of anxiety, epilepsy, sleep induction, and anesthesia, etc.
they are often called sedative-hypnotics or just anxiolytics.
Cross tolerance occurs bt all the CNS sedative including the barbiturates, benzodiazepines (BZDs), and ethanol
- Barbiturates
- Benzodiazepines
- Other.
what is MOA of Barbiturates?
enhance the function of γ-aminobutyric acid (GABA) in CNS by enhancing the duration of chloride channel openings. This action hyper-polarizes the cell, and causes an increase in inhibition of CNS.
- produces sedation at low doses. at high doses, can cause hypnosis, coma, death
- suppress respiration by inhibiting the hypoxic and Co2 responses to chemoreceptors.
- induce liver P-450 system, so metabolism of other drugs will be altered in its presence
- physical dependence occurs after chronic use
*selection of particular barbiturate depends on duration of action of agent, which in turn depends on its lipid solubility
what are withdrawal symptoms of Barbiturates?
anxiety, nausea, vomiting, hypotension, seizures and psychosis
CV collapse may develop leading to death
Phenobarbital
Anxiolytic and Hypnotic drug
long acting Barbiturate (1-2 days)
used as anticonvulsant in epilepsy
Amobarbital
Anxiolytic and Hypnotic drug
short acting Barbiturate (3-8 hours)
used in anesthesia
what are MOA, actions of Benzodiazepines?
what is the difference bt Barbiturates and Benzodiazepines?
used most widely as anxiolytic drug
MOA: bind to specific site on Neuronal GABA receptors. this binding enhances the affinity of GABA receptors for GABA, resulting in more frequent opening of chloride channels. The increased influx of chloride causes increased inhibition.
Actions: all BZD reduce anxiety and cause sedation.
Difference: unlike Barbiturates, BZD reduce anxiety at doses that do not produce sedation. Some agents are used as anti-epileptic agents and some are used in induction of anesthesia. Duration of action and pharmacokinetic properties are important considerations in selecting drugs to be used.
Dependence and withdrawal symptoms of Benzodiazepines?
physical and psychological dependence of BZD can occur.
withdrawal: confusion, anxiety, agitation, restlessness,
BZD with short half-lives induce more abrupt and severe withdrawal reactions than do drugs with longer half-lives
Diazepam(valium)
Anxiolytic and Hypnotic drug
long acting Benzodiazepines
used for anxiety disorders, skeletal muscle spasm, spasticity from degenerative disorders such as MS and cerebral palsy
Alprazolam
Anxiolytic and Hypnotic drug
long acting Benzodiazepines
used as antidepressant, anxiolytic, tx of panic attacks
Oxazepam
Anxiolytic and Hypnotic drug
long acting Anxiolytic and Hypnotic drug
useful for tx elderly patients and patients with liver dysfunction bc it does not rely on liver for metabolism
which Benzodiazepines are used in tx of status epilepticus and alcoholic withdrawal?
tx of status epilepticus: Diazepam & Lorazepam
alcoholic withdrawal: Chlordiazepoxide
what are the advantages of using ZOLPIDEM? what effect of this drug has been seen on vegetative state of patient?
this is Anxiolytic drug
used for short term tx of insomnia, show no tolerance or withdrawal effects.
it is said to WAKE persistent vegetative state with brain injuries.
what are MOA and use of Flumazenil?
Anxiolytic and Hypnotic drug
a competitive Benzodiazepines receptro antagonist.
can be sued to reverse the sedative effects of Benzodiazepines after anesthesia or after overdose with BZD