NEET MDS Lessons
Pharmacology
Beta - Adrenergic Blocking Agents
Mechanisms of Action
- Initial decrease in cardiac output, followed by reduction in peripheral vascular resistance.
- Other actions include decrease plasma renin activity, resetting of baroreceptors, release of vasodilator prostaglandins, and blockade of prejunctional beta-receptors.
Advantages
- Documented reduction in cardiovascular morbidity and mortality.
- Cardioprotection: primary and secondary prevention against coronary artery events (i.e. ischemia, infarction, arrhythmias, death).
- Relatively not expensive.
Considerations
- Beta blockers are used with caution in patients with bronchospasm.
- Contraindicated in more than grade I AV, heart block.
- Do not discontinue abruptly.
Side Effects
- Bronchospasm and obstructive airway disease.
- Bradycardia
- Metabolic effects (raise triglyerides levels and decrease HDL cholesterol; may worsen insulin sensitivity and cause glucose intolerance). Increased incidence of diabetes mellitus.
- Coldness of extremities.
- Fatigue.
- Mask symptoms of hypoglycemia.
- Impotence.
Indications
- First line treatment for hypertension as an alternative to diuretics.
- Hypertension associated with coronary artery disease.
- Hyperkinetic circulation and high cardiac output hypertension (e.g., young hypertensives).
- Hypertension associated with supraventricular tachycardia, migraine, essential tremors, or hypertrophic cardiomyopathy.
Beta adrenergic blocker Drugs
Atenolol 25-100
Metoprolol 50-200
Bisoprolol 2.5-10
EPHEDRINE
It act indirectly and directly on α and β receptors. It increases blood pressure both by peripheral vasoconstriction and by increasing the cardiac output. Ephedrine also relaxes the bronchial smooth muscles.
Ephedrine stimulates CNS and produces restlessness, insomnia, anxiety and tremors.
Ephedrine produces mydriasis on local as well as systemic administration.
Ephedrine is useful for the treatment of chronic and moderate type of bronchial asthma, used as nasal decongestant and as a mydriatic without cycloplegia. It is also useful in preventing ventricular asystole in Stokes Adams syndrome.
Anesthesia agents
1. Inhalation anesthetics (volatile anesthetics)
- gases : N2O, xenon
- Fluids (vaporisers)
2. Intravenous anesthetics
- Barbiturans : thiopental
- Others : propofol, etomidat
3. Pain killers
- Opioids: fentanyl, sufentanil, alfentanil, remifentanil, morphine
- Non Steroid Anti Inflamatory Drugs: ketonal, paracetamol
4. Relaxants
- Depolarising : succinilcholine
- Non depolarising : atracurium, cisatracurium, vecuronium, rocuronium
5. adiuvants
-benzodiazepins: midasolam, diazepam
Drugs used to induce vomiting
In case of poisoning with noncorrosive agents, and assuming incomplete absorption of the poison has taken place, induction of vomiting can be carried out. One of the drugs used for this purpose is emetine which causes irritation of the upper gut and, on absorption, it also acts on CTZ.
Chemotherapeutic agents (or their metabolites) can directly activate the medullary chemoreceptor trigger zone or vomiting center; several neuroreceptors, including dopamine receptor Type 2 and serotonin Type 3 (5-HT3) from cell damage(GIT and pharynx) play roles in vomiting.
ANTICHOLINERGIC DRUGS
Blocks the action of Ach on autonomic effectors.
Classification
Natural Alkaloids - Atropine. Hyoscine
Semi-synthetic deriuvatives:- Homatropine, Homatropine methylbromide, Atropine methonitrate.
Synthetic compounds
(a) Mydriatics - Cyclopentolate. Tropicamide.
(b) Antisecretory - Antispasmodics - Propantha1ine. Oxy-phenonium, Pirenzipine.
c) Antiparkinsonism- Benzotopine, Ethopropazine, Trihexyphenidyl, Procyclidine, Biperiden
Other drugs with anticholinergic properties • Tricyclic Antidepressants • Phenothiazines • Antihistaminics • Disopyramide
MUSCARINIC RECEPTORS SUBTYPES & ANTAGONISTS
• M 1 Antagonists – Pirenzepine, Telenzepine, dicyclomine, trihexyphenidyl
• M 2 Antagonists – Gallamine, methoctramine
• M 3 Antagonists – Darifenacin, solifenacin, oxybutynin, tolterodine
Pharmacological Actions
CNS - stimulation of medullary centres like vagal. respiratory. vasomotor and inhibition of vestibular excitation and has anti-motion sickness properties.
CVS - tachycardia.
Eye - mydriasis
Smooth muscles - relaxation of the muscles receiving parnsympathetic motor innervation.
Glands - decreased secretion of sweat and salivary glands
Body Temperature - is increased as there is stimulation of temperature regulating centre.
Respiratory System- Bronchodilatation & decrease in secretions. For COPD or Asthma - antimuscarinic drugs are effective
GIT - Pirenzepine & Telenzepine - decrease gastric secretion with lesser side effects.
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
Fourth Generation:
These are extended spectrum antibiotics. They are resistant to beta lactamases.
Cefipime