NEET MDS Lessons
Pharmacology
Mixed Narcotic Agonists/Antagonists
These drugs all produce analgesia, but have a lower potential for abuse and do not produce as much respiratory depression.
A. Pentazocine
- Has a combination of opiate analgesic and antagonist activity.
- Orally, it has about the same analgesic potency as codeine.
- In contrast to morphine, cardiac workload tends to increase due to an increase in pulmonary arterial and cerebrovascular pressure. Blood pressure and heart rate both also tend to increase.
- Adverse reactions to Pentazocine
• Nausea, vomiting, dizziness.
• Psychotomimetic effects, such as dysphoria, nightmares and visual hallucinations.
• Constipation is less marked than with morphine.
B. Nalbuphine
- Has both analgesic and antagonist properties.
- Resembles pentazocine pharmacologically.
- Analgesic potency approximately the same as morphine.
- Appears to be less hypotensive than morphine.
- Respiratory depression similar to morphine, but appears to peak-out at higher doses and to reach a ceiling.
- Like morphine, nalbuphine reduces myocardial oxygen demand. May be of value following acute myocardial infarction due to both its analgesic properties and reduced myocardial oxygen demand.
- Most frequent side effect is sedation.
C. Butorphanol
- Has both opiate agonist and antagonist properties.Resembles pentazocine , pharmacologically., 3.5 to 7 times more potent than morphine., Produces respiratory depression, but this effect peaks out with higher doses. The respiratory depression that does occur lasts longer than that seen following morphine administration.
- Butorphanol, like pentazocine, increases pulmonary arterial pressure and possibly the workload on the heart.
- Adverse reactions include sedation, nausea and sweating.
D. Buprenorphine
- A derivative of eto`rphine. Has both agonist and antagonist activity. 20 to 30 times more potent than morphine.Duration of action only slightly longer than morphine, but respiratory depression and miosis persist well after analgesia has disappeared.
- Respiratory depression reaches a ceiling at relatively low doses.
- Approximately 96% of the circulating drug is bound to plasma proteins.
- Side effects are similar to other opiates:
- sedation, nausea, vomiting,
- dizziness, sweating and headache.
Factors affecting onset and duration of action of local anesthetics
pH of tissue
pKa of drug
Time of diffusion from needle tip to nerve
Time of diffusion away from nerve
Nerve morphology
Concentration of drug
Lipid solubility of drug
GENERAL ANESTHETICS
General anesthesia often involves more than one drug to get different, favourable effects.
Premedication is often used to:
1. Treat anxiety - Benzodiazapenes
2. Reduce pain - Opiod anaglesics such as morphine
3. Produce muscle paralysis -E.g. Tubocurare
4. Reduce secretions
Induction of anesthesia is often done via intravenous anesthetics, which are quick and easy to administer.
Maintenance of anesthesia involves inhalation agents.
Prototype Agents:
Volatile Anesthetics:
• Nitrous Oxide
• Ether
• Halothane
• Enflurane
• Isoflurane
Injectable Anesthetics:
• Thiopental
• Ketamine
• Etomidate
• Propofol
• Midazolam
DOBUTAMINE
It is a derivative of dopamine and has relatively β1 -selective action and it also activates α1 receptors and do not have D1 receptor agonistic property. It increases the force of myocardial contraction and cardiac output without significant change in heart rate, blood pressure and peripheral resistance. It is used as inotropic agent and for short term management of CHF and also in patients who are unresponsive to digitalis.
Celecoxib
is a highly selective COX-2 inhibitor and primarily inhibits this isoform of cyclooxygenase, whereas traditional NSAIDs inhibit both COX-1 and COX-2. Celecoxib is approximately 10-20 times more selective for COX-2 inhibition over COX-1.
Being a sulphonamide can cause skin rash & hypersensitivity rxn., occasional oedema& HT.
Indication
Osteoarthritis ( 100‐200mg BID ) , rheumatoid arthritis, dysmenorrhea, acute gouty attacks, acute musculoskeletal pain.
Treatment modifications to consider if there are concerns regarding vasoconstrictors
- Monitor blood pressure and heart rate preoperatively
- Minimize administration of epinephrine or levonordefrin
- Monitor blood pressure and heart rate 5 min after injection
- May re-administer epinephrine or levonordefrin if blood pressure and heart rate are stable
- Continue to monitor as required
- Consider limiting epinephrine to 0.04 mg, levonordefrin to 0.2 mg
- Avoid epinephrine 1:50,000
- Never use epinephrine-impregnated retraction cord
Mucosal protective agents.
These are locally active agents that help heal gastric and duodenal ulcers by forming a protective barrier between the ulcers and gastric acid, pepsin, and bile salts. They do not alter the secretion of gastric acid. These drugs include sucralfate and colloid bismuth compounds. (e.g. tripotassium, dicitratobismuthate). Colloidal bismuth compounds additionally exert bactericidal action against H.pylori. Also, Prostaglandins have both antisecretory and mucosal protective effects.
Example: Misoprostol- used for prevention of NSAID – induced ulcer.
- Drugs that exert antimicrobial action against H.pylori such as amoxicillin, metronidazole, clarithromycin and tetracycline are included in the anti-ulcer treatment regimens.