Therapeutic breadth

The therapeutic range of a drug is the difference between its therapeutic dose and a dose that leads to a toxic effect. The greater the therapeutic range, the safer a drug is. This is generally given as the "therapeutic quotient", which is calculated as follows:

${\displaystyle \mathrm {Therapeutischer\ Quotient} ={{LD_{50}} \over {ED_{50}}}}$

Here, ED ₅₀ ( median effective dose ), the dose, the desired therapeutic effect occurs in 50% of individuals, and LD ₅₀ ( median lethal dose ), the dose at which 50% of the individuals die.

It should be noted here that the therapeutic quotient of LD ₅₀ and ED _{50 is} in many cases not regarded as absolutely reliable for determining the therapeutic range, since the so-called effect curves of the ED and the LD can be steeply different and thus a wrong result for the danger can come out. It is more reliable to use the therapeutic index , a quotient of LD ₅ (lethal effect in 5% of the test persons) and ED ₉₅ (desired effect in 95% of the test persons). U. wrong results regarding the dangerousness, albeit to a much smaller extent, are obtained. Absolutely reliable statements about the therapeutic safety of a drug can only be obtained from the entire course of the dose-effect curve and the dose-lethality curve and not necessarily from the calculation of a quotient.

Medicines with a wide therapeutic range include, for example, glucocorticoids , penicillin , other β-lactam antibiotics , the cardiac glycoside strophanthin and the oral administration of diazepam . Drugs with a narrow therapeutic range are, for example, the digitalis cardiac glycosides , lithium and theophylline . When using them, the effects must therefore be carefully monitored, in some cases by laboratory tests of the blood level . Many narcotics are characterized by a narrow therapeutic index. Their effect, the depth of anesthesia, must therefore be constantly monitored over time by the anesthetist; see Anesthesia (patient monitoring) .

Since the definition of the therapeutic quotient is based on the death of the treated person, the protective quotient was defined analogously to the toxic dose . The protective quotient represents a more realistic safety assessment for a drug approval , but uses the less clear measure of a previously defined scale of toxic effects.

${\displaystyle \mathrm {Protektiver\ Quotient} ={{TD_{50}} \over {ED_{50}}}}$

See also

• Drug Monitoring
• Bioequivalence , bioavailability
• The pharmacodynamics is the study of the effect of drugs in the body.
• The pharmacokinetics describes how rapidly and to what extent after administration of a substance that subsequently in the blood plasma occurs and in various body tissues and where and in what way he again excreted is.
• Adverse effects (old: side effects)

Individual evidence

1. ^ Heinz Lüllmann, Klaus Mohr, Martin Wehling: Pharmacology and Toxicology. 16th edition. Georg Thieme Verlag, 2006, ISBN 978-3-13-368516-0 , p. 16.
2. ↑ Ernst Mutschler, Gerd Geisslinger, Heyo K. Kroemer, Monika Schäfer-Korting: drug effects. Textbook of pharmacology and toxicology. Wissenschaftliche Verlagsgesellschaft, 2001, ISBN 3-8047-1763-2 .

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !