Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
15 Cards in this Set
- Front
- Back
Therapeutic Dose |
Average dose required to produce the therapeutic effect, in adult male. |
|
Loading Dose |
Initial large dose to build up therapeutic blood level (LD = Vd * Css) Vd: apparent volume of destribution Css: steady state concentration |
|
Maintenance Dose |
daily dose required to maintain the therapeutic level (MD = Cl * Css * Tm) Cl = clearance Tm = time interval |
|
Minimal effective dose |
the lowest dose to produce therapeutic effect |
|
Maximal tolerated dose |
the largest dose without toxic effect |
|
Median Lethal dose |
the fatal dose in 50% of cases (kill 50% of animals) |
|
Uses of Median Lethal dose (LD50) |
- a measure of acute toxicity (the smaller, the more toxic) - determines the therapeutic index and safety margin - determines the GIT absorption (compare oral with IV) - Clinical trials usually start at one tenth of LD50 |
|
Therapeutic Index |
- the ratio of LD50 (the dose that produces toxicity in 50% of cases) to the ED50 ( the dose that produces an effective response in 50% of the cases) - is a measure of drug's safety, because a larger value indicates a wide margin between doses that are effective and doses that are toxic. |
|
Therapeutic Window |
a more clinically relevant index of safety, describes the dosage range between the minimum effective therspeutic dose, and the minimum toxic dose. |
|
Factors affecting Action & Dosage of drugs: |
1- Biological Variation 2- Age 3- Weight & Surface Area 4- Sex 5- Route of Administration 6- Time of Administration 7- Cumulation & Zero order Kinetics 8- Psychological factors 9- Pathological state 10- Allergy 11- Idiosyncracy 12- Intolerance (Supersensitivity) 13- Tolerance & Dependance 14- Drug Interactions |
|
Factors affecting Action & Dosage of drugs: 2- Age: Pediatrics differ from adult: |
- more body water, less fat, less plasma ptn, BBB more permeable, thin skin - less Renal clearance e.g. aminoglycosides - less HME activity Grey Baby syndrome - behave differently to some drugs e.g. amphetamine produces sedation - can tolerate some drugs than adults e.g. atropine & digitalis |
|
Factors affecting Action & Dosage of drugs: 2- Age: Geriatrics differ from adult: |
- dec. GIT motility, blood flow & HCL secretion - dec. lean body weight, water & relative inc. in fat. - dec. HME activity & hepatic blood flow - dec, GFR & tubular secretion - inc. frequency of postural hypotension& dec. baroreceptor reflex - inc. sensitivity to CNS depressants
|
|
Factors affecting dosage and action of drugs:
4- Sex |
Females need smaller doses than males because more fat and estrogen inhibit HME.
Drugs specifically for females e.g. oxytocics and tocolytics. Drugs avoided by females in certain periods: - Menstruation Aspirin Bleeding - Pregnancy Oxytocics Cathartics Teratogenic Abortion and fetal anomalies. - Labour Morphine Barbiturates Neonatal asphyxia. - Lactation: Purgatives antihistaminics anticoagulants tetracyclines. |
|
Factors affecting Action and Dosage of the drug:
8- Psychological factors |
Placebo effect response to psychological rather than pharmacological effects.
Placebo is an inert preparation used for therapeutic effects in psychotherapy and for evaluation of new drugs (Dynamic or Psychic Effect). |
|
Factors affecting Action and Dosage of the drug:
9- Pathological state |
Some drugs act ONLY in the presence of disease.
Pathology may cause supersensitivity. |