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Pharmacology - NEETMDS- courses
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Pharmacology

Procaine penicillin Procaine penicillin is a combination of benzylpenicillin with the local anaesthetic agent procaine. This combination is aimed at reducing the pain and discomfort associated with a large intramuscular injection of penicillin.

Indications

respiratory tract infections where compliance with oral treatment is unlikely ,syphilis, cellulitis

Kinins
Peptide that are mediated in the inflammation.
Action of kinin:
On CVS: vasodilatation in the kidneys, heart, intestine, skin, and liver. It is 10 times active than histamine as vasodilator.

On exocrine and endocrine glands: kinin modulate the tone of pancreas and salivery glands and help regulate GIT motility, also affect the transport of water and electrolytes, glucose and amino acids through epithelial cell transport.

Itraconazole:

The drug may be given orally or intravenously.

Classification

I) Esters

 1. Formed from an aromatic acid and an amino alcohol.

 2. Examples of ester type local anesthetics:

 Procaine

Chloroprocaine

Tetracaine

Cocaine

Benzocaine- topical applications only

2) Amides

 1. Formed from an aromatic amine and an amino acid.

 2. Examples of amide type local anesthetics:

Articaine

Mepivacaine

Bupivacaine

Prilocaine

Etidocaine

Ropivacaine

Lidocaine

Propoxyphene

  • A methadone analog.Used orally to relieve mild to moderate pain.
  • A typical opiate, it does not possess anti-inflammatory or antipyretic actions, but has little or no antitussive activity.
  • Cannot be used parenterally because of irritant properties.
  • Has a low addiction potential primarily due to its lack of potency as an opiate.
  • The most common adverse side effects are:• dizziness, drowsiness, and nausea and vomiting. • these effects are more prominent in ambulatory patients.
  • Withdrawal symptoms have occurred in both adults and in neonates following use of the drug by the mother during pregnancy.
  • CNS depression is additive with other CNS depressants.

Pharmacology is the study of drugs and the way they interact with living systems.  Clinical pharmacology is the study of drugs in humans.

A drug is any chemical that can effect living processes.

Therapeutics: the medical use of drugs.

An ideal drug has several important properties.  Three of these properties are of utmost importance: effectiveness, safety and selectivity. 

Effectiveness: This is the most important quality that a drug can have.  Effectiveness refers to the drug's ability to do what it is supposed to do.

Safety:  Although no drug can be totally safe, proper usage can lessen the risks of adverse effects.

Selectivity:  A truly selective drug would have no side effects, and would effect only the body process' for which it is designed and given.  Therefore, there is no such thing as a selective drug.

Pharmacokinetics: The way the body deals with a drug.  Pharmacokinetics is concerned with the processes of absorption, distribution, metabolism and excretion.

Pharmacodynamics:  What a drug does to the body.

Pharmacokinetics and pharmacodynamics are two of the processes that determine how a person will respond to a drug.  Other factors include how a drug is administered (dose, route, and timing of administration), interactions with other drugs, and individual physiological variables (weight, age, function of body systems).

Sympathomimetics -Adrenergic Agents

The sympathomimetic or adrenergic or adrenomimetic drugs mimic the effects of adrenergic sympathetic nerve stimulation.
These are the  important group of therapeutic agents which may be used to maintain blood pressure and in certain cases of severe bronchial asthma. 

Mechanism of Action and Adrenoceptors 

The catecholamines produce their action by direct combination with receptors located on the cell membrane.  The adrenergic receptors are divided  into two main groups – alpha and beta. 
 alpha receptor - stimulation produces excitatory effect and 
 beta receptor -stimulation usually produces inhibitory effect. 
 
Alpha receptors: There are two major groups of alpha receptors, α1  and α2.
Activation of postsynaptic α1 receptors increases the intracellular concentration of calcium by activation of a phospholipase C in the cell membrane via G protein. 
α2 receptor is responsible for inhibition of renin release from the kidney and for central aadrenergically mediated blood pressure depression.

Beta  receptors: 

a. Beta 1  receptors have approximately equal affinity for adrenaline and noradrenaline and are responsible for myocardial stimulation and renin release.

b. Beta 2 -  receptors have a higher affinity for adrenaline than for noradrenaline and are responsible for bronchial muscle relaxation, skeletal muscle vasodilatation and uterine relaxation.

c. Dopamine receptors: The D1 receptor is typically associated with the stimulation of adenylyl cyclase. The important agonist of dopamine receptors is fenoldopam (D1) and bromocriptine (D2) and antagonist is clozapine (D4) .

Adrenergic drugs can also be classified into:

a. Direct sympathomimetics: These act directly on a or/and b adrenoceptors e.g. adrenaline, noradrenaline, isoprenaline, phenylephrine, methoxamine salbutamol etc.
b. Indirect sympathomimetics: They act on adrenergic neurones to release noradrenaline e.g. tyramine.
c. Mixed action sympathomimetics: They act directly as well as indirectly e.g. ephedrine, amphetamine, mephentermine etc.

Pharmacological Action of Sympathomimetics 

Heart: Direct effects on the heart are determined largely by β1 receptors.
Adrenaline increases the heart rate, force of myocardial contraction and cardiac output

Blood vessels: Adrenaline and noradrenaline constrict the blood vessels of skin and mucous membranes. 
 Adrenaline also dilates the blood vessels of the skeletal muscles on account of the preponderance of  β2 receptor 
 
Blood pressure: Because of vasoconstriction (α1) and vasodilatation (β2) action of adrenaline, the net result is decrease in total peripheral resistance.

Noradrenaline causes rise in systolic, diastolic and mean blood pressure and does not cause vasodilatation (because of no action on β2  receptors) and increase in peripheral resistance due to its a action.

Isoprenaline causes rise in systolic blood pressure (because of β1 cardiac stimulant action) but marked fall in diastolic blood pressure (because of b2 vasodilatation action) but mean blood pressure generally falls.

GIT: Adrenaline causes relaxation of smooth muscles of GIT and reduce its motility. 

Respiratory system: The presence of β2 receptors in bronchial smooth muscle causes relaxation and activation of these receptors by β2 agonists cause bronchodilatation.
Uterus: The response of the uterus to the atecholamines varies according to species

Eye: Mydriasis occur due to contraction of radial muscles of iris, intraocular tension is lowered due to less production of the aqueous humor secondary to vasoconstriction and conjunctival ischemia due to constriction of conjunctival blood vessels.

a. Urinary bladder: Detrusor is relaxed (b) and trigone is constricted (a) and both the actions tend to inhibit
micturition. 

b. Spleen: In animals, it causes contraction (due to its a action) of the splenic capsule resulting in increase in number of RBCs in circulation.

c. It also cause contraction of retractor penis, seminal vesicles and vas deferens.

d. Adrenaline causes lacrimation and salivary glands are stimulated. 

e. Adrenaline increases the blood sugar level by enhancing hepatic glycogenolysis and also by decreasing the uptake of glucose by peripheral tissues.
Adrenaline inhibits insulin release by its a-receptor stimulant action whereas it stimulates glycogenolysis by its b receptor stimulant action.

f. Adrenaline produces leucocytosis and eosinopenia and accelerates blood coagulation and also stimulates platelet aggregation.

Adverse Effects

Restlessness, anxiety, tremor, headache.
Both adrenaline and noradrenaline cause sudden increase in blood pressure, precipitating sub-arachnoid haemorrhage and occasionally hemiplegia, and ventricular  arrhythmias. 
May produce anginal pain in patients with ischemic heart disease. 

Contraindications

a. In patients with hyperthyroidism.
b. Hypertension.
c. During anaesthesia with halothane and cyclopropane.
d. In angina pectoris.

Therapeutic Uses

Allergic reaction: Adrenaline is drug of choice in the treatment of various acute allergic disorders by acting as a physiological antagonist of histamine (a known mediator of many hypersensitivity reactions). It is used in bronchial asthma, acute angioneurotic edema, acute hypersensitivity reaction to drugs and in the treatment of anaphylactic shock.

Bronchial asthma: When given subcutaneously or by inhalation, adrenaline is a potent drug in the treatment of status asthmaticus.

Cardiac uses: Adrenaline may be used to stimulate the heart in cardiac arrest.
Adrenaline can also be used in Stokes-Adam syndrome, which is a cardiac arrest occurring at the transition of partial to complete heart block. Isoprenaline or orciprenaline may be used for the temporary treatment of partial or complete AV block.

Miscellaneous uses:

a. Phenylephrine is used in fundus examination as mydriatic agent.
b. Amphetamines are sometime used as adjuvant and to counteract sedation caused by antiepileptics.
c. Anoretic drugs can help the obese people.
d. Amphetamine may be useful in nocturnal enuresis in children.
e. Isoxsuprine (uterine relaxant) has been used in threatened abortion and dysmenorrhoea.

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