Pharmacology - ALPHA & BETA BLOCKERS - ADRENERGIC ANTAGONISTS ( MADE EASY)

00:11:05
https://www.youtube.com/watch?v=41Xloc_vvX8

Resumo

TLDRLa conferència tracta sobre els antagonistes adrenèrgics, que s'uneixen als receptors adrenèrgics per prevenir la seva activació, dividint-se en blocos alfa i beta. Es descriuen els diferents tipus de bloquejadors alfa i beta, així com els seus usos terapèutics, com ara el tractament de la hipertensió, insuficiència cardíaca, i glaucoma. També s'expliquen els efectes secundaris associats i les propietats específiques de certs fàrmacs dins de cada categoria.

Conclusões

  • 🧪 Els antagonistes adrenèrgics bloquegen receptors evitant la seva activació.
  • 🌿 Es divideixen en bloquejadors alfa i beta amb diferents aplicacions clíniques.
  • 💊 Bloquejadors alfa redueixen la pressió arterial mitjançant vasodilatació.
  • ❤️ Bloquejadors beta són essencials en patologies cardiovasculars com hipertensió i angina.
  • 🧠 Alguns bloquejadors beta penetren al sistema nerviós central, útils per a profilaxi de migranyes.
  • 👁️ Bloquejadors beta poden tractar el glaucoma reduint la pressió intraocular.
  • ⚠️ Bloquejadors no selectius poden causar broncoconstricció, no aptes per a persones amb asma.
  • 🎯 La selectivitat dels bloquejadors afecta el seu ús i efectes secundaris.
  • 🧬 Alguns beta bloquejadors de tercera generació tenen efectes vasodilatadors addicionals.
  • 🔗 L'activitat simpaticomimètica intrínseca proporciona opcions per a pacients amb bradicàrdia.

Linha do tempo

  • 00:00:00 - 00:05:00

    En aquesta conferència es parla dels antagonistes adrenèrgics, que també s'anomenen simpaticolítics. Aquests lliguen als receptors adrenèrgics però, en comptes d'estimular-los, eviten la seva activació. Els antagonistes adrenèrgics es poden dividir en dos grups principals: bloquejadors alfa i bloquejadors beta. Dins dels bloquejadors alfa, hi ha els bloquejadors alfa-1, que bloquegen la unió de noradrenalina als receptors del múscul llis, provocant vasodilatació i reducció de la pressió arterial. S'usen en el tractament de la hipertensió, i es poden subdividir en bloquejadors alfa-selectius i no selectius. Els exemples inclouen Phentolamine i Phenoxybenzamine, que són útils en el tractament de la hipertensió causada per feocromocitoma, i tenen diferències notables en la seva duració d'efectes. També es discuteixen els efectes sobre els receptors alfa-2 i les diferències entre els bloquejadors alfa-1 i els bloquejadors alfa-2, que tenen aplicacions limitades en humans.

  • 00:05:00 - 00:11:05

    Després de discutir els bloquejadors alfa, la conferència passa als bloquejadors beta, que es poden subdividir tant en agents selectius com no selectius i en diferents generacions. Els bloquejadors beta són inhibidors competitius en els receptors beta adrenèrgics i contraresten els efectes de les catecolamines com adrenalina i noradrenalina, reduint els efectes simpàtics principalment en el sistema cardiovascular. S'utilitzen en el tractament de la hipertensió, insuficiència cardíaca, infarts, angina i arrítmies, entre altres aplicacions com el tractament del glaucoma. Els bloquejadors beta de primera generació són no selectius, afectant els receptors beta-1 i beta-2, i poden provocar broncoconstricció. Els de segona generació són selectius per als receptors beta-1, començant a anomenar-se cardioselectius, més adequats per a pacients amb malaltia pulmonar crònica. La tercera generació inclou tant agents no selectius com selectius, però es diferencia perquè també produeixen vasodilatació. Es discuteixen altres característiques com les activitats simpaticomimètiques intrínseques d'alguns bloquejadors beta.

Mapa mental

Vídeo de perguntas e respostas

  • Què són els antagonistes adrenèrgics?

    Són substàncies que s'uneixen als receptors adrenèrgics sense activar-los, bloquejant-ne l'activació.

  • Quina és la funció dels bloquejadors alfa-1?

    Bloquegen la unió de la norepinefrina als músculs llisos, causant vasodilatació i disminució de la pressió arterial.

  • Què són els bloquejadors beta no selectius?

    Són bloquejadors que afecten tant els receptors beta-1 com beta-2 a tot el cos.

  • Quins són exemples de bloquejadors alfa-1 selectius?

    Prazosin, Doxazosin, Terazosin, Tamsulosin, Alfuzosin i Silodosin.

  • Quina diferència hi ha entre Phentolamina i Phenoxybenzamine?

    Phentolamina és un antagonista reversible mentre que Phenoxybenzamine és irreversible.

  • Quins efectes secundaris poden causar els bloquejadors alfa-1?

    Poden causar hipotensió ortostàtica, mals de cap i congestió nasal.

  • Per a què s'utilitzen els bloquejadors beta de tercera generació?

    S'utilitzen per a hipertensió i tenen propietats antioxidants que els fan útils per a insuficiència cardíaca.

  • Què és l'activitat simpaticomimètica intrínseca?

    És la capacitat d'alguns beta bloquejadors de bloquejar i feblement estimular els receptors beta-1 i beta-2.

  • Quina és l'aplicació clínica principal dels bloquejadors beta no selectius?

    Reducció de la freqüència cardíaca i de la demanda d'oxigen del múscul cardíac.

  • Hi ha beta-2 bloquejadors clínicament útils?

    No, actualment no existeixen beta-2 bloquejadors amb utilitat clínica.

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  • 00:00:00
    in this lecture I'm going to talk about adrenergic antagonists so let's get
  • 00:00:05
    right into it adrenergic antagonists also called sympatholytics
  • 00:00:10
    bind to adrenergic receptors but instead of stimulating
  • 00:00:14
    them they actually prevent their activation and just like with adrenergic
  • 00:00:20
    agonists we can divide antagonists based on their affinity for alpha or beta
  • 00:00:25
    receptors so we can divide adrenergic antagonists into two main groups that is
  • 00:00:33
    alpha blockers and beta blockers so let's start with alpha blockers first
  • 00:00:40
    alpha-1 adrenergic antagonists block the binding of norepinephrine to the
  • 00:00:46
    smooth muscle receptors which results in vasodilation and thus lowering of blood
  • 00:00:51
    pressure this is why alpha blockers are useful in the treatment of hypertension
  • 00:00:58
    now alpha blockers can be subdivided into two groups that is non-selective
  • 00:01:03
    alpha blockers and selective alpha blockers as you might have guessed
  • 00:01:10
    non-selective agents can block both alpha-1 and alpha-2 receptors example of these
  • 00:01:16
    are Phentolamine and Phenoxybenzamine which are used in the treatment of
  • 00:01:21
    hypertension specifically caused by pheochromocytoma which is a tumor of the
  • 00:01:26
    adrenal glands that secrete norepinephrine and epinephrine now we
  • 00:01:32
    know that through alpha-1 blockade these drugs cause vasodilation but since they
  • 00:01:37
    are non-selective they also block alpha-2 receptors which as you may remember
  • 00:01:41
    from the previous lecture are mainly located on presynaptic nerve endings
  • 00:01:47
    now norepinephrine acts on alpha-2 receptors to inhibit its own release so
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    blockade of these receptors results in more norepinephrine release
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    norepinephrine then can stimulate beta-1 receptors on the heart this is why
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    non-selective drugs such as Phentolamine and Phenoxybenzamine can cause
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    tachycardia and even cardiac arrhythmias now
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    the main difference between these two drugs is that Phenoxybenzamine is a
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    irreversible antagonist and the only way the body can overcome its effects is by
  • 00:02:24
    making new adrenergic receptors which takes about 24 hours or so on the other
  • 00:02:29
    hand Phentolamine is a reversible antagonist and that's why its effect
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    lasts only about four hours or so now let's move on to selective alpha
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    blockers and let's discuss alpha-1 blockers first so these agents
  • 00:02:47
    selectively and reversibly block alpha-1 receptors located mainly in vascular
  • 00:02:53
    smooth muscle which reduces peripheral resistance and leads to decrease in
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    blood pressure and they also block receptors in the smooth muscle of the
  • 00:03:03
    bladder neck and prostate gland which causes smooth muscle there to relax
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    leading to relief of the urinary difficulties associated with benign
  • 00:03:12
    prostatic hypertrophy BPH for short or simply enlarged prostate
  • 00:03:18
    now examples of alpha-1 selective blockers include Prazosin Doxazosin
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    Terazosin Tamsulosin Alfuzosin and Silodosin and note that this
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    ending with "-osin" is a pretty good giveaway when it comes to identifying
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    alpha-1 blocker now the first three of these that is Prazosin Doxazosin and
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    Terazosin are effective treatment for hypertension but have lesser effects
  • 00:03:51
    on relieving symptoms of enlarged prostate on the other hand Tamsulosin
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    Alfuzosin and Silodosin have little effect on blood pressure but are much
  • 00:04:02
    more effective for relieving symptoms associated with enlarged prostate and
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    this is because these agents have increased selectivity for alpha-1
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    receptors in the prostate specifically alpha-1a subtype now when it comes to
  • 00:04:19
    side effects orthostatic hypotension is one of the main concerns when initiating
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    alpha-1 blocker although it's not as severe as that
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    observed with non-selective alpha blockers additionally vasodilation
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    produced by alpha-1 blockers can lead to headaches and nasal congestion
  • 00:04:38
    finally what about alpha-2 selective blockers well alpha-2 selective
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    blockers have very limited clinical application in humans and they're used
  • 00:04:48
    mainly in research one example of alpha-2 blocker that you may encounter is
  • 00:04:53
    Yohimbine which can be found in some dietary supplements however there is not
  • 00:04:59
    much beneficial evidence supporting its use in humans on the other hand
  • 00:05:04
    Yohimbine is used sometimes in veterinary medicine to reverse sedative effects
  • 00:05:09
    of alpha-2 agonist such as Xylazine now let's switch gears and let's move on to
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    beta blockers so just like alpha blockers beta blockers can also be
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    subdivided into selective and non-selective agents however unlike
  • 00:05:28
    alpha blockers beta blockers can also be grouped in generations beta blockers are
  • 00:05:34
    competitive inhibitors at beta adrenergic receptors and they counter
  • 00:05:39
    the effects of catecholamines such as epinephrine and norepinephrine which
  • 00:05:43
    leads to decrease in sympathetic effects mainly on cardiovascular system this is
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    why beta blockers are useful in the treatment of hypertension heart failure
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    heart attacks angina and cardiac arrhythmias additional uses include
  • 00:05:59
    treatment of glaucoma and migraine prophylaxis so now let's start by
  • 00:06:05
    discussing first generation beta blockers which also happen to be
  • 00:06:09
    non-selective that is they block beta-1 and beta-2 receptors throughout the body
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    example of these agents include Propranolol Pindolol or Nadolol
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    Sotalol and Timolol now practically all the applications of these agents are
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    based on blockade of beta-1 receptors on the heart which results in decreased
  • 00:06:31
    heart rate delayed conduction through AV node and reduced contractility so now
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    the final outcome is decreased cardiac output and decreased oxygen demand of
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    heart muscle besides being useful in treatment of hypertension angina and
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    arrhythmia note that Propranolol due to its lipophilicity
  • 00:06:52
    can also penetrate into the CNS and was found to be effective for
  • 00:06:56
    migraine prophylaxis on the other hand Timolol when applied topically to the
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    eye was found to decrease intraocular pressure which is why it is often used
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    for a treatment of glaucoma however all that being said let's not forget
  • 00:07:13
    about blockade of beta-2 receptors by these non-selective agents and as you may
  • 00:07:19
    recall beta-2 receptors are predominant in lungs so their blockade can actually
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    lead to bronchoconstriction for this reason these non-selective beta blockers
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    are not recommended in patients with COPD or asthma now let's move on to the
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    second generation beta blockers which happen to be selective for beta-1
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    receptors and because of that we also call them cardio-selective beta blockers
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    now this cardio-selectivity makes these agents more suitable in patients with
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    chronic lung disease however keep in mind that at high enough doses this beta-1
  • 00:07:57
    selectivity can be lost and beta-2 receptor blockade may occur example of
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    these agents include Atenolol Acebutolol Bisoprolol Esmolol and Metoprolol now
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    let's move on to the third generation beta blockers and here you need to pay
  • 00:08:19
    special attention because things can get a little tricky so unlike the first
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    generation group that included non-selective agents and unlike the second
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    generation group that included selective agents the third generation group
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    includes both non-selective and selective beta blockers however what
  • 00:08:42
    makes the third generation beta blockers different from the other two is that
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    they also act on blood vessels to cause vasodilation so here we have
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    non-selective agents such as Carvedilol and Labetalol which
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    produce peripheral vasodilation by blocking not only beta but also alpha-1
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    receptors and on the other hand we have beta-1 selective agents such as
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    Nebivolol which produce vasodilation by inducing the release of nitric oxide
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    from endothelial cells and Betaxolol which is thought to produce vasodilation
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    by additionally blocking calcium channels and just as a side note here
  • 00:09:26
    Betaxolol due to its ability to decrease intraocular pressure when
  • 00:09:31
    applied topically to the eye just like Timolol it is often prescribed for
  • 00:09:35
    glaucoma but the bottom line here is that vasodilation produced by the
  • 00:09:41
    third generation beta blockers make these agents especially effective in
  • 00:09:46
    treatment of hypertension furthermore Carvedilol and Nebivolol have been also
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    shown to have antioxidant properties which make them beta blockers of choice
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    for heart failure alongside commonly prescribed Bisoprolol and Metoprolol lastly
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    I wanted to briefly discuss intrinsic sympathomimetic activity of couple beta
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    blockers namely Pindolol and Acebutolol now these two beta blockers are a
  • 00:10:15
    little special in that they have ability to not only block but also to weakly
  • 00:10:21
    stimulate both beta-1 and beta-2 receptors which leads to diminished effect
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    on cardiac rate and cardiac output this so called intrinsic sympathomimetic
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    activity can actually be beneficial in patients who cannot tolerate other beta
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    blockers because of pre-existing bradycardia or heart block and now
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    before we end you may wonder well what about beta-2 blockers and the short
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    answer is at this time we don't have clinically useful beta-2 blockers and
  • 00:10:57
    with that I wanted to thank you for watching I hope you enjoyed it and as
  • 00:11:02
    always stay tuned for more videos
Etiquetas
  • antagonistes adrenèrgics
  • bloquejadors alfa
  • bloquejadors beta
  • simpatolítics
  • vasodilatació
  • hipertensió
  • insuficiència cardíaca
  • glaucoma
  • activitat simpaticomimètica
  • norepinefrina