NEET MDS Lessons
Pharmacology
Serotonin or 5-hydroxytryptamine (5-HT)
It is a neurotransmitter, widely distributed in the CNS, beginning in the midbrain and projecting into thalamus, hypothalamus, cerebral cortex, and spinal cord. CNS serotonin is usually an inhibitory neurotransmitter and is associated with mood, the sleep-wake cycle.
Serotonin is thought to produce sleep by inhibiting CNS activity.
In the blood, 5-HT is present in high concentration in platelets (regulator of platelets function) and also high concentration in intestine
Pharmacological effects:
Smooth muscles. 5-HT stimulates the G.I smooth muscle; it increases the peristaltic movement of intestine.
Serotonin contracts the smooth muscle of bronchi;
Blood vessels. If serotonin is injected i.v, the blood pressure usually first rises, because of the contraction of large vessels and then falls because of arteriolar dilatation. Serotonin causes aggregation of platelets.
Specific agonists
- Sumatriptan a selective 5-HT1D used in treatment of acute migraine.
- Buspirone a selective 5-HT1A used in anxiety.
- Ergotamine is a partial agonist used in migraine. It acts on 5-HT1A receptor.
Nonspecific 5-HT receptor agonist
o Dexfenfluramine used as appetite suppressant.
Specific antagonists
o Spiperone (acts on 1A receptor) and
o Methiothepin (acts on 1A, 1B, 1D receptors)
Doxycycline
Commonly prescribed for infections and to treat acne. treat urinary tract infections, gum disease, and other bacterial infections such as gonorrhea and chlamydia., as a prophylactic treatment for infection by Bacillus anthracis (anthrax). It is also effective against Yersinia pestis and malaria.
Ampicillin offered a broader spectrum of activity than either of the original penicillins and allowed doctors to treat a broader range of both Gram-positive and Gram-negative infections. Ampicillin is often used in molecular biology as a test for the uptake of genes (e.g., by plasmids) by bacteria (e.g., E. coli)
Procoagulant Drugs:
Desmospressin Acetate
• Is a synthetic analogue of the pituitary antidiuretic hormone (ADH).
• Stimulates the activity of Coagulation Factor VIII
• Use for treatment of hemophilia A with factor VIII levels less than or equal to 5%, treatment of hemophilia B or in clients who have factor VIII antibodies. Treatment of severe classic von Willebrand's disease (type I) and when an abnormal molecular form of factor VIII antigen is present. Use for type IIB von Willebrand's disease.
Agonist, Antagonist, and Partial Agonists
Agonists: molecules that activate receptors. A drug that mimics the body's own regulatory processes.
Antagonists: produce their effects by preventing receptors activation by endogenous regulatory molecules and drugs. Block activation of receptors by agonists.
Noncompetive Antagonist: Bind irreversibly to receptors, and reduce the maximal response that an agonist can elicit.
Competitive Antagonist: Bind reversibly to receptors, competing with agonists for binding sites.
Partial Agonists: Have moderate intrinsic activity, the maximal effect that a partial agonist can produce is lower than that of a full agonist. Act as antagonists as well as agonists.
Antidepressant Drugs
Drug treatment of depression is based on increasing serotonin (5-HT) or NE (or both) at synapses in selective tracts in the brain. This can be accomplished by different mechanisms.
Treatment takes several weeks to reach full clinical efficacy.
1. Tricyclic antidepressants (TCAs)
a. Amitriptyline
b. Desipramine
c. Doxepin
d. Imipramine
e. Protriptyline
2. Selective serotonin reuptake inhibitors (SSRIs)
a. Fluoxetine
b. Paroxetine
c. Sertraline
d. Fluvoxamine
e. Citalopram
3. Monoamine oxidase inhibitors (MAOIs)
a. Tranylcypromine
b. Phenelzine
4. Miscellaneous antidepressants
a. Bupropion
b. Maprotiline
c. Mirtazapine
d. Trazodone
e. St. John’s Wort
Antimania Drugs
These drugs are used to treat manic-depressive illness.
1. Lithium
2. Carbamazepine
3. Valproic acid
CHOLINERGIC DRUGS
Produce actions similar to Acetylcholine (Ach)
Cholinergic Agonists
1 Acetylcholine 2 Methacholine 3. Carbachol 4 Bethnechol
Alkaloids
1.Muscarine 2 Pilocarpine 3. Arecoline
MECHANISM OF ACTION
I Heart- hyperpolarizes the SA node and decreases the rate of diastolic depolarisation. thus the frequcncy of impulse generation is decreased. bradycardia.
2 Blood vessels- vasodilatation
3. Smooth muscles - increased contraction. increased tone. increased peristalsis.
4. Glands- increased sweating. increased lacrimation.
5 Eye- contraction of the circular muscle of iris (miosis).
Nicotinic action
Autonomic ganglia - stimu1ation of sympathetic and parasympathetic system.
Skeletalmuscles - contraction of fibres.
CNS..No effect as it does not penetrate the blood-brain barrier.
Toxic effects
Flushing. sweating.salivation. cramps. belching. involuntary mictuirition. defaccation.
Contraindication
1.. Anginapectoris- decreases the coronary flow.
2 Pepticulcer - increases the gastric secretion
3 Asthma- bronchoconstriction
4 Hyperthyroidisim
Cholinomimetic Alkaloids
Pilocarpine
Prominent muscarinic actions. causes marked sweating. salivation. Increase of secretions. small doses cause fall in BP but higher doses increase in BP. Applied to the eye cause miosis. fall in intraocular tension
Uses
I. .Open angle glaucoma
2. To counteract mydriasis
Anticholinesterase
They inhibit the enzyme cholinestrase and prolong the action of Ach
Reversible
Physostigamine, Ncostigamine, Pyridostigamine, Ambenonium, Edrophonium, Demecarium
Irreverible
Dyflos. Echothiphate.
Pharmacological Actions
I Ganglia - persistent depolarisation of ganglionic nicotinic receptors.
2 CVS - unprcdictable as Muscarinic-I receptor causes bradycardia but ganglionic stimulation
tachycardia.
3. Skeletal muscles - as Ach is not destroyed and rebinds to the same receptor or it diffuses on to the neighbouring receptors to cause repetitive firing. twitching and fasciculations.
Uses
I As miotic
a) Glaucoma : Acute congestive (narrow angle) glaucoma, Chronic simple (wide angle) glaucoma
b) Counter act atropine mydriasis.
2) Post operative paralytic ileus
3) Myasthenia gravis
4) Postoperativedecurarization
5) Cobra bite
6) Belladona poisoning
7) Other drug overdoses