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Potency And Efficacy

Efficacy measure the maximum pharmacologic effect produced by a given drug. EC50 of a drug is the concentration of the drug that produce 50% of maximum effect. The drugs with lower EC50 have more potency.

Antagonists

Competitive antagonists bind to receptors without producing biological effects. Increasing the concentration of agonists will reverse the effect of competitive antagonists. In contrast the effect of noncompetitive antagonists cannot be reversed by agonist

Bioavailability And Intravenous Versus Oral Administration

Bioavailability is defined as the percentage of the drug which reach systematic circulation. At steady state the intravenous administration rate equal to clearance multiply by concentration. Bioavailability of the drug affect the rate of administration of

Digoxin
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Digoxin

The mechanism of action of digoxin drug which increase the contractility of cardiac muscle. Its action involve closure of Na/K ATPase channels which eventually close the efflux of calcium Ca ions and increase the concentration of intracellular calcium ion

Dosing Interval

Continuous intravenous infusion reach the steady state concentration after around 4 half-lives. Single daily intravenous injection will reach steady state after four half-lives but with more peaks and troughs. More frequent administrations results in less

Loading Dose

In some serious clinical conditions there is need to reach the target plasma concentration rapidly. Therefore a high dose called loading dose is given for once followed by usual maintenance dose to avoid reaching the toxic concentration

Neuromuscular Junction Blockers

Acetylcholine binds to its nicotinic receptor to induce contraction of skeletal muscle. Group of drugs called neuromuscular junction blockers competitively block the nicotinic receptors and induce relaxation. Increase the concentration of acetylcholine at

Parkinson Disease

The main target of antiparkinsonian drugs is to increase the dopamine concentration and activity in the brain. Levodopa is transformed into dopamine in the brain, DDC and COMT inhibitors decrease the peripheral metabolism of levodopa. Dopamine agonists a

Steady State Equation

At steady state the administration rate equals to elimination rate. Therefore the plasma concentration of the drug remain constant. At steady state concentration infusion rate equal to plasma concentration multiplied by clearance.

Therapeutic Window

For any drug to exert a proper therapeutic effect, its plasma concentration must lie in target therapeutic window above the minimum therapeutic concentration and below the toxic level

Volume Of Distribution

Volume of distribution measure the ability of various drugs with different sizes and charges to distribute through body fluids. Apparent volume of distribution Vd is calculated by dividing the amount of the drug administered on the plasma concentration of