Drugs Mimicking SAN Flashcards
What are drugs mimicking San referred to as and what effects can they induce
Sympathomimetic or adrenergic drugs
1-drugs mimicking adrenergic receptors
2-indirectly inactivating adrenergic receptors
3-can act both directly and indirectly
How can sympathomimetic drugs indirectly activate adrenergic receptors
Inc uptake of exogenous catecholamine
Inhibit re uptake of released catecholamine
Adv of non catecholamine agents
Prolonged duration of action being non metabolized by COMPT or MAO enzymes
Examples of the direct acting endogenous catecholamines and what they act on
Adrenaline: on all adrenergic receptors
Noradrenaline: strong affinity for a1 with less effect in B1 receptors
Dopamine: dose dependent activity on D1 B1 and a1 receptors
What is adrenaline used for
▪️In anaphylactic shock: adrenaline give IM as its the physiological antagonist of histamine
Reverses hypotension and bronchoconstriction by acting in a1 and B2 receptors
Prevents further release of histamine through b2 activation
▪️cardiac arrest: intracardiac administration of adrenaline
When is noradrenaline used
▪️In septic shock as it induces a strong vasopressor effect by activation of a1 receptors
▪️in hypovolemic shock
When is dopamine used
In hypovolemic shock: maintains blood flow to kidney through vasodilator effect of D1 receptors
Elevates bp by activation of a1 and b1 receptors
How can local administration of adrenaline be helpful
Local anesthesia to prolong action of anesthetic and prevent systemic absorption
Epistaxis as a local hemostatic agent
What are the features of indirectly acting agents and what are they
Inc release of noradrenaline from synaptic vesicles and have longer duration of action and can be taken orally
Pseudoephedrine
Methamphetamine
What does pseudoephedrine do
Used orally for its decongestant effect in case of common cold
OTC
Should be used cautiously in hypertension patients
What does methamphetamine do
Highly addictive
Used in treatment of ADHD
What do selective a receptor agonists generally do
Dissects vascular effects from cardiac actions and helps to avoid arrythmogenic potential of activating B1 receptors
Elevates blood pressure in acute hypotensive states
Phenylephrine(IV)
Methoxamine (IV and IM)
Used in chronic hypotension
Midodrine(oral)
Used topically to relieve nasal and conjunctival congestion
Xylometazoline(nasal)
Oxymetazoline & phenylephrine(ocular and nasal)
Decreases systemic blood pressure by decreasing sympathetic outflow in treatment of hypertension (in brain)
Clonidine
A methyl dopa
Used in spinal cord to dec skeletal muscle spasticity by inhibiting release of excitatory neurotransmitters in treatment of spastic disorders
Tizanidine
Used in eye to dec IOP by dec aqueous humor formation and dec drainage in treatment of glaucoma
Topical brimonidine
Why do we use selective b receptor agonists
Clinically useful to achieve cardiac and bronchial effects without vasoconstrictor effect of a1 receptor activation
What is the selective b1 agonist and what is it used for
Dobutamine used for positive inotropic effect as in cariogenic shock or acute heart failure
What is the selective b2 agonist and what is it used for
Induces
Bronchodilation in case of treatment of bronchial asthma by using salbutamol and terbutaline (short acting)
Salmeterol (long acting)
Uterine relaxant to prevent premature labor by using ritrodine and tetrabutaline
8 adverse reactions and toxicity
1-severe hypertension and headache and cerebral hemorrhage with non selective agents or with selective a1
2-cardiac arrhythmia of non selective and selective b1
3-reflex bradycardia with a1receptors
4-skeletal muscle tremors and tachycardia for selective b2 agonists
5-CNS excitation in form of fear and anxiety
6-high doses of amphetamines produces physchosis and convulsions
7-specific hypersensitivity reactions
8- topical nasal decongestants can:
-sting and burn and dry nostrils
- atrophy of cilia of nasal mucosa
-rhinitis medicamentosa
