NEET MDS Lessons
Pharmacology
Sympatholytics And Alpha Adrenergic Blockers
Types
1. Alpha 1-receptor blockers: prazocin,doxazocin.
2. Centrally acting alpha 2- agonists: methyldopa, clonidine.
3. Peripherally acting adrenergic antagonists: reserpine.
4. Imidazoline receptor agonists: rilmenidine, moxonidine.
Advantages
- Alpha1- receptor blockers and imidazoline receptor agonists improve lipid profile and insulin sensitivity.
- Methyldopa: increases renal blood flow. Drug of choice during pregnancy.
- Reserpine: neutral metabolic effects and cheap.
Indications:
- Diabetes mellitus: alpha1- receptor blockers, imidazoline receptor agonists.
- Dyslipidemia: alpha 1- receptor blockers, imidazoline receptor agonists.
- Prostatic hypertrophy: alpha 1- receptor blockers.
- When there is a need for rapid reduction in blood pressure: clonidine.
Side Effects
- Prazocin: postural hypotension, diarrhea, occasional tachycardia, and tolerance (due to fluid retention).
- Methyldopa: sedation, hepatotoxicity, hemolytic anemia, and tolerance.
- Reserpine: depression, lethargy, weight loss, peptic ulcer, diarrhea, and impotence
- Clonidine: dry mouth, sedation, bradycardia, impotence, and rebound hypertension if stopped suddenly.
Considerations
- Prazocin, methyldopa, and reserpine should be combined with a diuretic because of fluid retention.
Direct Arterial Vasodilators
Types: hydralazine, diazoxide, nitroprusside, and minoxidil
Insulin
Insulin is only given parenterally (subcutaneous or IV) Various preparations have different durations of action
|
Preparation |
Onset (hrs) |
Peak (hrs) |
Duration (hrs) |
| Lispro (rapid-acting) | 15 min | 0.5-1.5 | 3-4 |
| Regular (short-acting) | 0.5-1 | 2-4 | 5-7 |
| NPH (intermediate) | 1-2 | 6-12 | 18-24 |
| Glargine (long-acting) | 1 | None | >24 |
Mechanism
bind transmembrane insulin receptor
activate tyrosine kinase
phosphorylate specific substrates in each tissue type
liver
↑ glycogenesis
store glucose as glycogen
muscle
↑ glycogen and protein synthesis
↑ K+ uptake
fat
increase triglyceride storage
Clinical use
type I DM
type II DM
life-threatening hyperkalemia
increases intracellular K+
stress-induced hyperglycemia
Toxicity
hypoglycemia
hypersensitivity reaction (very rare)
Insulin Synthesis
first generated as preproinsulin with an A chain and B chain connected by a C peptide.
c-peptide is cleaved from proinsulin after packaging into vesicles leaving behind the A and B chains
Methicillin
Methicillin is an antibiotic related to penicillin and other beta-lactam containing antibiotics. It is often used to treat infections caused by bacteria carrying an antibiotic resistance, e.g., staphylococci. As methicillin is deactivated by gastric acid, it has to be administered by injection.
Uses Methicillin serves a purpose in the laboratory to determine antibiotic sensitivity in microbiological culture.
PHARYNGEAL DEMULCENTS
Administered in the form of lozenges, cough drops and cough linctus.
Produce soothing action on throat directly and by increasing the flow of saliva and provide symptomatic relief from dry cough.
EXPECTORANT
Expectorants are the drugs which increase the production of bronchial secretion and reduce its viscosity to facilitate its removal by coughing.
ANTITUSSIVES
They are central cough suppressants and act centrally to raise the threshold of cough centre and inhibit the cough reflex by suppressing the coordinating cough centre in the medulla oblongata.
Codeine - it depresses cough centre but is less constipating and abuse liability is low.
Pholcodeine is similar to codeine in efficacy and is longer acting. It has no analgesic or addicting property.
Noscapine is another opium alkaloid of benzylisoquinoline group. It is used as antitussive with no analgesic and drug abuse or drug dependence property.
Dextromethorphan is a synthetic compound and its dextroisomer is used as antitussive and is as effective as codeine
Pipazethate is another synthetic compound of phenothiazine category used as antitussive with little analgesic and sedative properties.
ANTIHISTAMINICS
They do not act on cough centre but provide relief due to their sedative and anticholinergic action.
BRONCHODILATORS
Bronchodilators are helpful in individuals with cough and bronchoconstriction due to bronchial hyperreactivity. They help by improving the effectiveness of cough in clearing secretions.
Midazolam -Intravenous Anesthetics
Midazolam is a benzodiazepine used for preoperative sedation, induction of anesthesia, or maintenance of anesthesia in short procedures.
Heroin (diacetyl morphine)
Heroin is synthetically derived from the natural opioid alkaloid morphine
Largely owing to its very rapid onset of action and very short half-life, heroin is a popular drug of abuse
It is most effective when used intravenously
Heroin is rapidly deacetylated to 6-monoacetyl morphine and morphine, both of which are active at the mu opioid receptor
More lipid soluble than morphine and about 2½ times more potent. It enters the CNS more readily.
Needle selection
Nerve blocks:
Inferior alveolar- 25 G short (LLU technique)
PSA- 25 G short
Mental/Incisive- 25 G short
Palatal- 27/30 G short/ultrashort
Gow-Gates/Akinosi- 25 G long
Infraorbital- 25 G long
Field Block:
ASA 25/27 short
Infiltration:
Infiltration/SP 25/27 short
PDL/Intraosseous
PDL 27/30 short
Intraosseous 30 short/ultrashort