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In pharmacokinetics, a maintenance dose is the maintenance rate [mg/h] of drug administration equal to the rate of elimination at steady state. This is not to be confused with dose regimen, which is a type of drug therapy in which the dose [mg] of a drug is given at a regular dosing interval on a repetitive basis. Continuing the maintenance dose for about 4 to 5 half-lives (t½) of the drug will approximate the steady state level. [1] One or more doses higher than the maintenance dose can be given together at the beginning of therapy with a loading dose. [2]
A loading dose is most useful for drugs that are eliminated from the body relatively slowly. Such drugs need only a low maintenance dose in order to keep the amount of the drug in the body at the appropriate level, but this also means that, without an initial higher dose, it would take a long time for the amount of the drug in the body to reach that level.
The required maintenance dose may be calculated as:
Where:
MD | is the maintenance dose rate [mg/h] |
Cp | = desired peak concentration of drug [mg/L] |
CL | = clearance of drug in body [L/h] |
F | = bioavailability |
For an intravenously administered drug, the bioavailability F will equal 1, since the drug is directly introduced to the bloodstream. If the patient requires an oral dose, bioavailability will be less than 1 (depending upon absorption, first pass metabolism etc.), requiring a larger loading dose.
Dofetilide is a class III antiarrhythmic agent. It is marketed under the trade name Tikosyn by Pfizer, and is available in the United States in capsules containing 125, 250, and 500 µg of dofetilide. It is not available in Europe or Australia. In the United States it is only available by mail order or through specially trained local pharmacies.
In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation.
Levothyroxine, also known as L-thyroxine, is a manufactured form of the thyroid hormone thyroxine (T4). It is used to treat thyroid hormone deficiency (hypothyroidism), including Hashimoto's disease and a severe form known as myxedema coma. It may also be used to treat and prevent certain types of thyroid tumors. It is not indicated for weight loss. Levothyroxine is taken by mouth or given by intravenous injection. Maximum effect from a specific dose can take up to six weeks to occur.
Prasugrel, sold under the brand name Effient in the US, Australia and India, and Efient in the EU) is a medication used to prevent formation of blood clots. It is a platelet inhibitor and an irreversible antagonist of P2Y12 ADP receptors and is of the thienopyridine drug class. It was developed by Daiichi Sankyo Co. and produced by Ube and marketed in the United States in cooperation with Eli Lilly and Company.
Alpha-methyl-p-tyrosine (AMPT) is a tyrosine hydroxylase enzyme inhibitor and is therefore a drug involved in inhibiting the catecholamine biosynthetic pathway. AMPT inhibits tyrosine hydroxylase whose enzymatic activity is normally regulated through the phosphorylation of different serine residues in regulatory domain sites. Catecholamine biosynthesis starts with dietary tyrosine, which is hydroxylated by tyrosine hydroxylase and it is hypothesized that AMPT competes with tyrosine at the tyrosine-binding site, causing inhibition of tyrosine hydroxylase.
Biological half-life is the time taken for concentration of a biological substance to decrease from its maximum concentration (Cmax) to half of Cmax in the blood plasma, and is denoted by the abbreviation .
In pharmacokinetics, a loading dose is an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a lower maintenance dose.
Acecainide is an antiarrhythmic drug. Chemically, it is the N-acetylated metabolite of procainamide. It is a Class III antiarrhythmic agent, whereas procainamide is a Class Ia antiarrhythmic drug. It is only partially as active as procainamide; when checking levels, both must be included in the final calculation.
Pharmacokinetics, sometimes abbreviated as PK, is a branch of pharmacology dedicated to determining the fate of substances administered to a living organism. The substances of interest include any chemical xenobiotic such as: pharmaceutical drugs, pesticides, food additives, cosmetics, etc. It attempts to analyze chemical metabolism and to discover the fate of a chemical from the moment that it is administered up to the point at which it is completely eliminated from the body. Pharmacokinetics is the study of how an organism affects a drug, whereas pharmacodynamics (PD) is the study of how the drug affects the organism. Both together influence dosing, benefit, and adverse effects, as seen in PK/PD models.
Delorazepam, also known as chlordesmethyldiazepam and nordiclazepam, is a drug which is a benzodiazepine and a derivative of desmethyldiazepam. It is marketed in Italy, where it is available under the trade name EN and Dadumir. Delorazepam (chlordesmethyldiazepam) is also an active metabolite of the benzodiazepine drugs diclazepam and cloxazolam. Adverse effects may include hangover type effects, drowsiness, behavioural impairments and short-term memory impairments. Similar to other benzodiazepines delorazepam has anxiolytic, skeletal muscle relaxant, hypnotic and anticonvulsant properties.
Difloxacin (INN), marketed under the trade name Dicural, is a second-generation, synthetic fluoroquinolone antibiotic used in veterinary medicine. It has broad-spectrum, concentration dependent, bactericidal activity; however, its efficacy is not as good as enrofloxacin or pradofloxacin.
An equianalgesic chart is a conversion chart that lists equivalent doses of analgesics. Equianalgesic charts are used for calculation of an equivalent dose between different analgesics. Tables of this general type are also available for NSAIDs, benzodiazepines, depressants, stimulants, anticholinergics and others as well.
The plateau principle is a mathematical model or scientific law originally developed to explain the time course of drug action (pharmacokinetics). The principle has wide applicability in pharmacology, physiology, nutrition, biochemistry, and system dynamics. It applies whenever a drug or nutrient is infused or ingested at a relatively constant rate and when a constant fraction is eliminated during each time interval. Under these conditions, any change in the rate of infusion leads to an exponential increase or decrease until a new level is achieved. This behavior is also called an approach to steady state because rather than causing an indefinite increase or decrease, a natural balance is achieved when the rate of infusion or production is balanced by the rate of loss.
Vortioxetine, sold under the brand names Trintellix and Brintellix among others, is a medication used to treat major depressive disorder. Effectiveness is viewed as similar to that of other antidepressants. In the United Kingdom, it is only recommended in people who have not improved sufficiently on two other antidepressants. It is taken by mouth.
In pharmacology the elimination or excretion of a drug is understood to be any one of a number of processes by which a drug is eliminated from an organism either in an unaltered form or modified as a metabolite. The kidney is the main excretory organ although others exist such as the liver, the skin, the lungs or glandular structures, such as the salivary glands and the lacrimal glands. These organs or structures use specific routes to expel a drug from the body, these are termed elimination pathways:
Gabapentinoids, also known as α2δ ligands, are a class of drugs that are derivatives of the inhibitory neurotransmitter gamma-Aminobutyric acid (GABA) which block α2δ subunit-containing voltage-dependent calcium channels (VDCCs). This site has been referred to as the gabapentin receptor, as it is the target of the drugs gabapentin and pregabalin.
Elagolix, sold under the brand name Orilissa, is a gonadotropin-releasing hormone antagonist medication which is used in the treatment of pain associated with endometriosis in women. It is also under development for the treatment of uterine fibroids and heavy menstrual bleeding in women. The medication was under investigation for the treatment of prostate cancer and enlarged prostate in men as well, but development for these conditions was discontinued. Elagolix is taken by mouth once or twice per day. It can be taken for up to 6 to 24 months, depending on the dosage.
The pharmacology of estradiol, an estrogen medication and naturally occurring steroid hormone, concerns its pharmacodynamics, pharmacokinetics, and various routes of administration.
The pharmacokinetics of progesterone, concerns the pharmacodynamics, pharmacokinetics, and various routes of administration of progesterone.
The pharmacology of testosterone, an androgen and anabolic steroid (AAS) medication and naturally occurring steroid hormone, concerns its pharmacodynamics, pharmacokinetics, and various routes of administration.