Posology Introduction and Factors
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Questions and Answers

What term describes the phenomenon where a drug's effect is neutralized by another drug acting on the same physiological system?

  • Tolerance
  • Idiosyncrasy
  • Tachyphylaxis
  • Antagonism (correct)

Idiosyncrasy refers to a normal response to a drug that aligns with its expected pharmacological action.

False (B)

What type of tolerance occurs only with the oral route of drug administration?

Pseudo tolerance

When a drug is given repeatedly at short intervals, the phenomenon where the pharmacological response decreases is called __________.

<p>tachyphylaxis</p> Signup and view all the answers

Match the following concepts with their definitions:

<p>Antagonism = Opposing effects of drugs on the same system Idiosyncrasy = Extraordinary drug response different from expected Tolerance = Increased dose needed for the same effect Tachyphylaxis = Decreased response after repeated doses</p> Signup and view all the answers

Which of the following is NOT a characteristic of drug tolerance?

<p>Increased response to a drug (C)</p> Signup and view all the answers

Salicylates can reduce body temperature even when an individual’s temperature is normal.

<p>False (B)</p> Signup and view all the answers

The dose of a drug given in pharmacopoeia is based on average maximum quantity to be administered to an adult within __________ hours.

<p>24</p> Signup and view all the answers

What does Posology deal with?

<p>Amount of medication administered (B)</p> Signup and view all the answers

Elderly patients generally require higher doses of hypnotics due to increased drug sensitivity.

<p>False (B)</p> Signup and view all the answers

Name a factor that can influence the dose of a drug administered to a patient.

<p>Age</p> Signup and view all the answers

The average dose is usually mentioned in terms of mg per kg of _____ weight.

<p>body</p> Signup and view all the answers

Which of the following factors does NOT influence drug dosage?

<p>Favorite Food (D)</p> Signup and view all the answers

Match the following age groups with their drug sensitivity characteristics:

<p>Newborns = Sensitive due to immature hepatic and renal functions Children = Generally require less dosage compared to adults Elderly = Sensitive to certain drug effects like hypnotics</p> Signup and view all the answers

Women react to drugs in the same way as men, except during pregnancy.

<p>False (B)</p> Signup and view all the answers

What is the term used for the phenomenon where drug effects diminish when the same dose is given repeatedly?

<p>Tolerance</p> Signup and view all the answers

Why are intravenous (I.V) doses typically smaller than oral doses?

<p>I.V doses might enhance the chances of drug toxicity. (B)</p> Signup and view all the answers

Which formula is specifically designed for calculating the dose of infants up to 2 years of age?

<p>Fried's formula (B)</p> Signup and view all the answers

Drugs are always ineffective when taken during or after a meal.

<p>False (B)</p> Signup and view all the answers

Dilling’s formula is applicable for children aged 4 to 20 years.

<p>True (A)</p> Signup and view all the answers

What type of drugs should be taken before meals according to the information?

<p>Antacid drugs</p> Signup and view all the answers

What does Clark's formula use to calculate the pediatric dose?

<p>Body weight</p> Signup and view all the answers

The phenomenon where two or more drugs' effects sum together is called __________.

<p>additive effect</p> Signup and view all the answers

Match the drug with its potential issue in patients with specific conditions:

<p>Streptomycin = Toxic effect in renal impairment Digitalis = Toxicity due to accumulation Barbiturates = Prolonged effect in liver disease Aminophylline = Additive effect with ephedrine</p> Signup and view all the answers

The Cowling's formula for calculating a child's dose uses the age at next birthday divided by _____ to derive the dose.

<p>24</p> Signup and view all the answers

What is the primary age factor used in Young’s formula to calculate pediatric dosage?

<p>Age in years + 12 (C)</p> Signup and view all the answers

What is meant by 'synergism' in pharmacology?

<p>Combining two or more drugs to enhance their actions. (B)</p> Signup and view all the answers

Match the following formulas with their appropriate age range:

<p>Young's formula = Under 12 years Dilling's formula = 4 to 20 years Fried's formula = Up to 2 years Cowling's formula = Age at next birthday</p> Signup and view all the answers

The personality of a physician can influence the effect of medication.

<p>True (A)</p> Signup and view all the answers

Calculate the pediatric dose for a 6-year-old child if the adult dose is 300 mg using Young’s Rule.

<p>150 mg</p> Signup and view all the answers

Which drug is mentioned as having a major excretion route through the kidney?

<p>Streptomycin</p> Signup and view all the answers

Catzel's formula accounts for surface area to calculate the patient's dose.

<p>True (A)</p> Signup and view all the answers

Flashcards

Route of Administration

The effectiveness of a drug can be influenced by how it is given. For example, intravenous doses are often smaller than oral doses due to a higher risk of toxicity.

Time of Administration

The presence of food in the stomach can delay the absorption of some drugs. Some drugs should be taken on an empty stomach, while others should be taken with food.

Environmental Factors

Certain factors, like a patient's personality or a doctor's approach, can influence how effectively a drug works, especially for conditions that involve both the mind and body.

Presence of Disease

A patient's existing health conditions can modify a drug's effectiveness. For instance, liver disease can make some drugs stay in the body longer.

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Drug Accumulation

Repeated use of certain drugs over time can lead to dangerous accumulation in the body. This is because these drugs are eliminated slowly from the body.

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Additive Effect

When two drugs are given together and their combined effect is equal to the sum of their individual effects, it is called an additive effect.

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Synergism

When two drugs work together to produce a greater effect than each drug would individually, it is called synergism.

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Drug Combinations

Some drugs are more effective when combined with others. This allows for achieving a desired therapeutic outcome that might not be possible with a single drug.

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What is Posology?

Posology is the study of drug dosages. It determines the amount of medication needed for a desired effect.

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Why is a fixed drug dose not always possible?

The right dose can vary greatly depending on factors like age, weight, and even sex.

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Why are infants more sensitive to drugs than adults?

Newborns are very sensitive to drugs due to their immature liver and kidneys, which break down and eliminate medications. This can lead to drug buildup and toxicity.

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How does age impact drug sensitivity in the elderly?

Elderly individuals may experience increased sensitivity to some drug effects, like those from sleeping medications, potentially leading to confusion.

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How can sex affect drug response?

Women may respond differently to drugs than men, and special considerations are needed during menstruation, pregnancy, and lactation.

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What are some drug precautions during menstruation and pregnancy?

Drugs like potent laxatives (e.g., Aloes) should be avoided during menstruation, while others that affect the uterus (e.g., drastic purgatives, anti-malarials) are contraindicated during pregnancy.

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Why are certain drugs contraindicated during pregnancy and lactation?

Drugs affecting the baby through the placenta (e.g., alcohol, barbiturates, narcotics) should be avoided during pregnancy, while others (e.g., morphine, tetracycline) are avoided during lactation.

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How does body weight influence drug dosage?

Typical drug doses are often given based on weight (mg per kg), but this may not be accurate for obese people, children, or malnourished individuals. Their doses should be adjusted based on their specific weight.

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Young's Formula

This formula is used for children under 12 years old. It calculates the child's dose by considering their age and the adult dose.

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Dilling's Formula

This formula is used for children between 4 and 20 years old. It's considered easier and quicker to calculate than other formulas.

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Fried's Formula

This formula is used for infants up to 2 years old. It calculates the infant's dose based on their age in months.

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Cowling's Formula

This formula calculates a child's dose based on their age at their next birthday. It aims to estimate the appropriate dose.

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Clark's Formula (dose based on weight)

Clark's formula calculates a child's dose based on their weight in kilograms. It aims to adjust the dose based on body size.

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Dose proportionate to body surface area

This method calculates a child's dose based on their surface area. It's considered more accurate than age-based methods because surface area is a better indicator of body size.

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Catzel's Formula

This method calculates a child's dose based on their surface area and the average adult surface area (1.73 m²), offering a more precise method than age-based methods.

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Drug Antagonism

This phenomenon occurs when the action of one drug is counteracted by the action of another drug on the same physiological system.

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Idiosyncrasy

This is an unusual or unexpected response to a drug that is different from its typical effects.

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Drug Tolerance

When a larger than usual dose of a drug is needed to achieve the same effect as before, it's called tolerance. This happens because your body adapts to the drug.

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Tachyphylaxis

Repeatedly giving a drug at short intervals can lead to a decreased response, even with higher doses. This is called tachyphylaxis or acute tolerance.

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Metabolic Disturbance

Changes in the body's internal environment, like fluid balance, temperature, or acidity, can affect how a drug works. This is called metabolic disturbance.

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Drug Dosage

The dose of a drug listed in a pharmacopoeia represents the average maximum amount that can be safely given to an adult orally within 24 hours.

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Dose Calculation

Calculating the correct dose of a drug for a patient considers factors like age, weight, and body surface area.

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Dosage Adjustment

The dose of a drug can vary based on different factors, including age, weight, body surface area, and the individual's response to the medication.

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Study Notes

Posology Introduction

  • Posology is derived from Greek words "posos" (how much) and "logos" (science).
  • It's a branch of medical science focused on drug doses and quantities for desired effects.
  • Drug dosages can't be fixed due to individual variation (age, sex, disease severity, etc).
  • Standard doses in pharmacopoeias are average ranges, usually for oral administration within 24 hours.
  • Appropriate doses are needed for other routes of administration.

Factors Influencing Dose

  • Age
  • Sex
  • Body weight
  • Route of administration (e.g.IV vs oral)
  • Time of administration (with or without food)
  • Environmental factors
  • Emotional state
  • Disease presence
  • Accumulation potential
  • Additive effect
  • Synergistic effect
  • Antagonistic effect
  • Idiosyncratic response
  • Tolerance
  • Tachyphylaxis
  • Metabolic disturbances

Age

  • Neonates and pediatric patients are more sensitive to certain drugs due to immature hepatic and renal function.
  • This leads to slower inactivation and elimination, potentially causing accumulation and toxicity.
  • Children often require lower doses compared to adults.
  • The elderly are also more sensitive to drugs, sometimes exhibiting exaggerated effects (e.g. confusion from hypnotics).

Sex

  • Women may respond differently to drugs than men due to physiological differences.
  • Special care is needed during menstruation, pregnancy, and lactation.
  • Certain drugs may be contraindicated during pregnancy & lactation because of their effect on the baby.

Body Weight

  • Doses are often listed as a specific amount per kilogram of body weight for better patient tailoring.
  • This method isn't suitable for obese, underweight, or malnourished patients; adjustments are needed in these cases.

Route of Administration

  • Intravenous (IV) doses are often smaller than oral doses because of potential toxicities associated with IV.
  • Route of administration influences the effectiveness and speed of drug absorption and action.

Time of Administration

  • Food can delay drug absorption, and some drugs are best taken on an empty stomach. While this can't always be the case (e.g., iron, arsenic, cod liver oil).

Environmental Factors

  • A physician's personality and behavior can impact the effect of drugs, especially psychosomatic disorders.
  • Females are sometimes more emotionally reactive, thus requiring smaller doses for certain types of drugs.

Presence of Disease

  • Pre-existing conditions can change a drug's effect.
  • Modifications in dose might be needed based on the current disease and patient condition.

Accumulation

  • Repeated administration may cause drug accumulation in tissues, especially if excretion is slow.

Additive Effect

  • The combined effect of two or more drugs is equal to the sum of their individual effects.

Synergism

  • When the combined effect of two drugs is greater than the sum of the individual effects.

Antagonism

  • When one drug opposes the action of another.
  • This can be useful in certain poisonings.

Idiosyncrasy

  • Unexpected response to a drug with a unique or abnormal reaction. This can include allergies.

Tolerance

  • The need for a progressively larger dose of a drug to produce the same effect over time.

Tachyphylaxis

  • Decreased response to a drug after repeated administration at short intervals, possibly due to receptor blockage.

Metabolic Disturbances

  • Changes in water, electrolyte balance, and acid-base balance can alter drug action.

Calculation of Doses

  • Pharmacopoeia doses are generally averages for adults, taken orally within 24 hours.
  • Dose adjustment is necessary based on the patient's age, body weight, or surface area.
  • Doses should be carefully calculated.

Methods for Calculating Doses for Children

  • Young's formula
  • Dilling's formula
  • Fried's formula
  • Cowling's formula
  • Clark's Formula
  • Catzel's Formula

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Description

Explore the fundamentals of posology, the science of drug dosages tailored to individual needs. This quiz highlights various factors influencing drug dosing, including age, sex, and route of administration. Understand the importance of appropriate dosing for achieving desired therapeutic effects.

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