Nitrous Oxide (N2O)

MAC 100%, blood/gas solubility ratio 0.47
- An inorganic gas., low solubility in blood, but greater solubility than N2
- Inflammable, but does support combustion.
- Excreted primarily unchanged through the lungs.
- It provides amnesia and analgesia when administered alone.
- Does not produce muscular relaxation.
- Less depressant to both the cardiovascular system and respiratory system than most of the other inhalational anesthetics.
- Lack of potency and tendency to produce anoxia are its primary limitations.
- The major benefit of nitrous oxide is its ability to reduce the amount of the secondary anesthetic agent that is necessary to reach a specified level of anesthesia.

Sulfonylureas

1st generation
tolbutamide
chlorpropamide

2nd generation

glyburide
glimepiride
glipizide

Mechanism

glucose normally triggers insulin release from pancreatic β cells by increasing intracellular ATP
→ closes K+ channels → depolarization → ↑ Ca2+ influx → insulin release

sulfonylureas mimic action of glucose by closing K+ channels in pancreatic β cells 
→ depolarization → ↑ Ca2+ influx → insulin release

its use results in

↓ glucagon release
↑ insulin sensitivity in muscle and liver

Clinical use

type II DM

stimulates release of endogenous insulin 
cannot be used in type I DM due to complete lack of islet function

Toxicity

first generation

disulfiram-like effects
especially chlorpropamide

second generation

hypoglycemia
weight gain

Seizure classification:

based on degree of CNS involvement, involves simple ( Jacksonian; sensory or motor cortex) or complex symptoms (involves temporal lobe)

1.    Generalized (whole brain involved): 

a.    Tonic-clonic:

Grand Mal; ~30% incidence; unconsiousness, tonic contractions (sustained contraction of muscle groups) followed by clonic contractions (alternating contraction/relaxation); happens for ~ 2-3 minutes and people don’t breathe during this time

Drugs: phenytoin, carbamazepine, Phenobarbital, lamotrigine, valproic acid

Status epilepticus: continuous seizures; use diazepam (short duration) or diazepam + phenytoin

b.    Absence:

Petit Mal; common in children; frequent, brief lapses of consciousness with or without clonic motor activity; see spike and wave EEg at 3 Hz (probably relates to thalamocorticoreverburating circuit)

Drugs: ethosuximide, lamotrigine, valproic acid

c.    Myoclonic: uncommon; isolated clinic jerks associated with bursts of EEG spikes; 

Drugs: lamotrigine, valproic acid

d.    Atonic/akinetic: drop seizures; uncommon; sudden, brief loss of postural muscle tone
Drugs: valproic acid and lamotrigine

2.    Partial:  focal

a.    Simple:  Jacksonian; remain conscious; involves motor or sensory seizures (hot, cold, tingling common)

Drugs: carbamazepine, phenytoin, Phenobarbital, lamotrigine, valproic acid, gabapentin

b.    Complex: temporal lobe or psychomotor; produced by abnormal electrical activity in temporal lobe (involves emotional functions)

Symptoms: abnormal psychic, cognitive, and behavioral function; seizures consist of confused/altered behavior with impaired consciousness (may be confused with psychoses like schizophrenia or dementia)

Drugs: carbamazepine, phenytoin, laotrigine, valproic acid, gabapentin

Generalizations: most seizures can’t be cured but can be controlled by regular administration of anticonvulsants (many types require treatment for years to decades); drug treatment can effectively control seizures in ~ 80% of patients

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.

Serotonin-norepinephrine reuptake inhibitors(SNRIs)

e.g. venlafaxine and duloxetine
- Inhibit the reuptake of both 5-HT and norepinephrine 
- Has a more favourable adverse effect profile than TCAs

Norepinephrine reuptake inhibitor

e.g. bupropion, reboxetine

Monoamine receptor antagonists

e.g. mirtazapine, trazodone, mianserin

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