Dopamine (DA) is a dopaminergic (D1 and D2) as well as adrenergic ? and?1 (but not ?2 ) agonist.

The D1 receptors in renal and mesenteric blood vessels are the most sensitive: i.v. infusion of a low dose of DA dilates these vessels (by raising intracellular cAMP). This increases g.f.r. In addition, DA exerts a natriuretic effect by D1 receptors on proximal tubular cells.

Moderately high doses produce a positive inotropic (direct?1 and D1 action + that due to NA release), but the little chronotropic effect on the heart.

Vasoconstriction (?1 action) occurs only when large doses are infused.

At doses normally employed, it raises cardiac output and systolic BP with little effect on diastolic BP. It has practically no effect on nonvascular ? and ? receptors; does not penetrate the blood-brain barrier—no CNS effects.

Dopamine is used in patients with cardiogenic or septic shock and severe CHF wherein it increases BP and urine outflow.

It is administered by i.v. infusion (0.2–1 mg/min) which is regulated by monitoring BP and rate of urine formation

Moderately high doses of dopamine produce a positive inotropic (direct?1 and D1 action + that due to Noradrenaline release), but the little chronotropic effect on the heart.

Vasoconstriction (?1 action) occurs only when large doses are infused.

At doses normally employed, it raises cardiac output and systolic BP with little effect on diastolic BP. It has practically no effect on nonvascular ? and ? receptors; does not penetrate the blood-brain barrier—no CNS effects.

Drug A is a pure agonist for the receptor, with high intrinsic efficacy and affinity, according to the log-dose response curve.

Drug B, on the other hand, works as a competitive antagonist. It binds to the receptor but has no inherent efficacy. Drug A’s efficacy will not change, but its potency will be reduced.

A partial agonist is a drug with partial intrinsic efficacy and affinity for the receptor. Giving a partial agonist after a pure agonist will not increase receptor occupancy or decrease receptor activity, and thus will not affect drug A’s efficacy. The inverse agonist flumazenil can reverse all benzodiazepines.

An inverse agonist is a drug that binds to the receptor but has the opposite pharmacological effect.

A non-competitive antagonist is a drug that has affinity for a receptor but has different pharmacological effects and reduces the efficacy of an agonist for that receptor.

Prostacyclin is a strong vasodilator. It is administered as an intravenous infusion for critical ischemia. Commercially, it is available as sodium epoprodtenol.

Atrial Natriuretic peptide (ANP) hormone secreted from the atria, kidney, and neural tissues. It primarily acts on renal vessel to maintain normal blood pressure and reduce plasma volume by: increasing the renal excretion of salt and water, glomerular filtration rate, vasodilation, and by increasing the vascular permeability. It also inhibits the release of renin and aldosterone.

Indoramin is an alpha-adrenoceptor blocking agent. which act selectively on post-synaptic-alpha adrenoreceptor, leading to decease in peripheral resistance.

Angiotensin II is a vasoconstrictor, causing high sodium retention. It also increases the secretion of antidiuretic hormone (ADH) and aldosterone level.

Phenytoin, Carbamazepine, and Valproate act by inhibiting the sodium channels when these are open. These drugs also prolong the inactivated stage of these channels (Sodium channels are refractory to stimulation till these reach the closed/ resting phase from inactivated phase)

Carbamazepine is the drug of choice for partial seizures and trigeminal neuralgia

It can have neurotoxic side effects. Major neurotoxic effects include dizziness, headache, ataxia, vertigo, and diplopia

After single oral doses of carbamazepine, the absorption is fairly complete and the elimination half-life is about 35 hours (range 18 to 65 hours). During multiple dosing, the half-life is decreased to 10-20 hours, probably due to autoinduction of the oxidative metabolism of the drug.

It is metabolized in liver into active metabolite, carbamazepine-10,11-epoxide.

The measure of drug potency or therapeutic response is the ED95. This is defined as the dose of a neuromuscular blocking drug required to produce a 95% depression of muscle twitch height. The ED50 and ED90 describe a depression of twitch height by 50% and 90% respectively.

The ED95 (mg/kg) of the commonly used neuromuscular blocking agents are:

suxamethonium: 0.27
rocuronium: 0.31
vecuronium: 0.04
pancuronium: 0.07
cisatracurium: 0.04
mivacurium: 0.08

To begin, one must determine the child’s approximate weight. There are a variety of formulas to choose from. It is acceptable to use the advanced paediatric life support formula:

(age + 4) 2 = weight

A 5-year-old child will weigh around 18 kilogrammes.

The following are the appropriate doses of the drugs listed above:

Gentamicin (once daily) – 5-7 mg/kg = 90-126 mg and subsequent dose modified according to plasma levels
Ondansetron – 0.1 mg/kg, but a maximum of 4 mg as a single dose = 1.8 mg
Codeine should be administered orally at a dose of 1 mg/kg rather than intravenously, as the latter can cause ‘dangerous’ hypotension due to histamine release.
15 mg/kg paracetamol = 270 mg orally or intravenously (a loading dose of 20 mg/kg, or 360 mg, is sometimes recommended, which is not far short of the doses listed above).
Cefuroxime – the initial intravenous dose is 20 mg/kg (360 mg) depending on the indication (again, similar to the dose given in the answer options above).

Sodium-chloride symporter inhibitor.

The thiazide sensitive sodium chloride symporter is inhibited by thiazides at the proximal portion of the distal convoluted tubule leading to increased sodium and water excretion. Increased delivery of sodium to the distal portion of the distal convoluted tubule promotes potassium loss. This is why thiazides are associated with hyponatraemia and hypokalaemia.

Carbonic anhydrase inhibitors are used mainly in the treatment of glaucoma. They act on the proximal convoluted tubule to promote bicarbonate, sodium and potassium loss.

Sodium potassium chloride symporter is inhibited by Loop diuretics.
Epithelial sodium channels are inhibited by Amiloride.
Drugs which lead to nephrogenic diabetes insipidus such as lithium and demeclocycline, are Inhibitors of vasopressin.

Sevoflurane is highly fluorinated methyl isopropyl ether widely used as an inhalational anaesthetic. It is suggested that sevoflurane preconditioning occurs via the opening of mitochondrial Potassium ATP dependent channel similar to that of Ischemic Preconditioning protection.

Gentamicin is a broad-spectrum antibiotic whose mechanism of action involves inhibition of protein synthesis by binding to 30s ribosomes. Its major adverse effect is nephrotoxicity and ototoxicity

Aminoglycoside bind to 30s subunit of ribosome causing misreading of mRNA

Tetracyclines inhibit protein synthesis through reversible binding to bacterial 30s ribosomal subunits, which prevent binding of new incoming amino acids (aminoacyl-tRNA) and thus interfere with peptide growth.

Chloramphenicol binds to the 50s subunit and inhibits peptidyl transferase

Clindamycin binds to the 50s ribosomal subunit of bacteria and disrupts protein synthesis by interfering with the transpeptidation reaction, which thereby inhibits early chain elongation.