NEET MDS Lessons
Pharmacology
Antiemetics
Antiemetic drugs are generally more effective in prophylaxis than treatment. Most antiemetic agents relieve nausea and vomiting by acting on the vomiting centre, dopamine receptors, chemoreceptors trigger zone (CTZ), cerebral cortex, vestibular apparatus, or a combination of these.
Drugs used in the treatment of nausea and vomiting belong to several different groups. These include:
1. Phenothiazines, such as chlorpromazine, act on CTZ and vomiting centre, block dopamine receptors, are effective in preventing or treating nausea and vomiting induced by drugs, radiation therapy, surgery and most other stimuli (e.g. pregnancy).
They are generally ineffective in motion sickness.
Droperidol had been used most often for sedation in endoscopy and surgery, usually in combination with opioids or benzodiazepines
2. Antihistamines such as promethazine and Dimenhyrinate are especially effective in prevention and treatment of motion.
3. Metoclopramide has both central and peripheral antiemetic effects. Centrally, it antagonizes the action of dopamine. Peripherally metoclopramide stimulates the release of acetylcholine, which in turn, increases the rate of gastric. It has similar indications to those of chlorpromazine.
4. Scopolamine, an anticholinergic drug, is very effective in reliving nausea & vomiting associated with motion sickness.
5. Ondansetron, a serotonin antagonist, is effective in controlling chemical-induced vomiting and nausea such those induced by anticancer drugs.
6. Benzodiazepines: The antiemetic potency of lorazepam and alprazolam is low. Their beneficial effects may be due to their sedative, anxiolytic, and amnesic properties
BradyKinin
An endogenous vasodilator occurring in blood vessel walls.
At least two distinct receptor types, B1 and B2, appear to exist for BradyKinin
Roles of bradykinin:
1) Mediator of inflammation and pain.
2) Regulation of microcirculation.
3) Their production is interrelated with clotting and fibrinolysin systems.
4) Responsible for circulatory change after birth.
5) Involved in shock and some immune reactions.
Stimulants:
Amphetamines: amphetamine is a substrate of serotonin and NE uptake transporters so in cytoplasm, it competes for transport into storage vesicles → ↑ [ ] in cytoplasm then excess amines bind to membrane transporter and are transported out of cell
Drugs:
a. Dextroamphetamine: psychomotor stimulant (↓ fatigue), short-term weight loss, prevents narcolepsy
b. Methylphenidate (Ritalin): prevents narcolepsy, treatment for ADD and ADHD
c. Methamphetamine: psychomotor stimulant, abused widely (cheap, easy to make)
Side effects:
a. CNS: euphoria, anxiety, agitation, delirium, paranoia, panic, suicidal/homicidal impulses, psychoses, tolerance (develops rapidly to most CNS effects), physical dependence (not clinically relevant)
b. CV: headache, chills, arrhythmias and HTN (may be fatal)
Midazolam -Intravenous Anesthetics
Midazolam is a benzodiazepine used for preoperative sedation, induction of anesthesia, or maintenance of anesthesia in short procedures.
DOPAMINE
It is an immediate metabolic precursor of noradrenaline. It activates D1 receptors in several vascular beds, which causes vasodilatation. It acts on dopaminergic and other adrenergic receptors (α & β1).
Adverse effects of dopamine include nausea, vomiting, ectopic beats, anginal pain, tachycardia, palpitation and widened QRS.
Contraindications are atrial or ventricular tachyarrhythmias, hyperthyroidism and pheochromocytoma.
DIAGNOSIS
Affective disorders:
I. unipolar depression – depression alone
bipolar affective disorder – alternating II. bipolar affective disorder – alternating depression and mania
Diagnosis is based on
At least five of the following for 2 weeks
I. Depressed mood most of the day
II. Markedly diminished interest or pleasureII. Markedly diminished interest or pleasure
III. Significant weight loss or weight
IV. Insomnia or hypersomnia
V. Psychomotor agitation or retardation
VI. Fatigue or loss of energy
VII. Feelings of worthlessness or excessive guilt
VIII. Diminished ability to think or concentrate,
IX. Recurrent thoughts of death
Underlying biological basis for depression is a deficiency of the monoamine neurotransmitters norepinephrine and/or serotonin in the brain.
Characteristics of Opioid Receptors
mu1
Agonists : morphine phenylpiperidines
Actions: analgesia bradycardia sedation
mu2
Agonists : morphine phenylpiperidines
Actions: respiratory depression euphoria physical dependence
delta
Actions: analgesia-weak, respiratory depression
kappa
Agonists: ketocyclazocine dynorphin nalbuphine butorphanol
Actions: analgesia-weak respiratory depression sedation
Sigma
Agonists: pentazocine
Action: dysphoria -delerium hallucinations tachycardia hypertension
epsilon:
Agonists: endorphin
Actions: stress response acupuncture