NEET MDS Lessons
Pharmacology
Loop (High Ceiling) Diuretics
Loop diuretics are diuretics that act at the ascending limb of the loop of Henle in the kidney. They are primarily used in medicine to treat hypertension and edema often due to congestive heart failure or renal insufficiency. While thiazide diuretics are more effective in patients with normal kidney function, loop diuretics are more effective in patients with impaired kidney function.
Agent: Furosemide
Mechanism(s) of Action
1. Diuretic effect is produced by inhibit of active 1 Na+, 1 K+, 2 Cl- co-transport (ascending limb - Loop of Henle).
o This produces potent diuresis as this is a relatively important Na re-absorption site.
2. Potassium wasting effect
a. Blood volume reduction leads to increased production of aldosterone
b. Increased distal Na load secondary to diuretic effect
c. a + b = increase Na (to blood) for K (to urine) exchange which produces indirect K wasting (same as thiazides but more likely)
3. Increased calcium clearance/decreased plasma calcium
o secondary to passive decreases in loop Ca++ reabsorption.
o This is linked to inhibition of Cl- reabsorption.
o This is an important clinical effect in patients with ABNORMAL High Ca++
Inhalational Anesthetics
The depth of general anesthesia is directly proportional to the partial pressure of the anesthetic agent in the brain. These agents enter the body through the lungs, dissolve in alveolar blood and are transported to the brain and other tissues.
A. Rate of induction and rate of recovery from anesthesia:
1. The more soluble the agent is in blood, the more drug it takes to saturate the blood and the more time it takes to raise the partial pressure and the depth of anesthesia.
2. The less soluble the agent is in blood, the less drug it takes to saturate the blood and the less time it takes to raise the partial pressure and depth of anesthesia.
B. MAC (minimum alveolar concentration)
The MAC is the concentration of the anesthetic agent that represents the ED50 for these agents. It is the alveolar concentration in which 50% of the patients will respond to a surgical incision.
The lower the MAC the more potent the general anesthetic agent.
C. Inhalation Anesthetic Agents
- Nitrous Oxide
- Ether
- Halothane
- Enflurane
- Isoflurane
Buspirone
1. Short half-life (2–4 hours).
2. Relieves anxiety.
3. Does not act as an anticonvulsant.
4. Is not a good muscle relaxant.
5. Minimum abuse potential.
Ciclopirox:Ciclopirox is a synthetic antifungal agent for topical dermatologic use.
GLP-1 analogs
Exenatide
Mechanism
GLP-1 is an incretin released from the small intestine that aids glucose-dependent insulin secretion
basis for drug mechanism is the observation that more insulin secreted with oral glucose load compared to IV
Exenatide is a GLP-1 agonist
↑ insulin
↓ glucagon release
the class of dipeptidyl peptidase inhibitors ↓ degradation of endogenous GLP-1
e.g.) sitagliptin, -gliptins
Clinical use
type II DM
Toxicity
nausea, vomiting
pancreatitis
hypoglycemia
if given with sulfonylureas
Diphenoxylate (present in Lomotil)
- A meperidine congener
- Not absorbed very well at recommended doses.
- Very useful in the treatment of diarrhea.
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