PK7 Bioequivaence Flashcards

1
Q

What is the definition of bioavailability?

A

Bioavailability is the rate and extent to which a drug is absorbed from its formulation and becomes available at the site of action.

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2
Q

What factors influence bioavailability?

A

Drug formulation, administration route, physicochemical properties, metabolism, distribution, and elimination.

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3
Q

How is bioavailability (F) calculated?

A

F = (Quantity of unchanged drug reaching systemic circulation / Quantity of administered drug) * 100.

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4
Q

What is the bioavailability of intravenous (IV) administration?

A

100% (F = 1) because the entire dose reaches systemic circulation.

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5
Q

What is first-pass metabolism?

A

The metabolism of a drug before it reaches systemic circulation, occurring in the liver and gut wall.

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6
Q

What is AUC, and why is it important?

A

Area Under the Curve (AUC) represents total drug exposure over time and is used to assess bioavailability.

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7
Q

How is absolute bioavailability calculated?

A

F = (AUC_oral / AUC_IV) * (Dose_IV / Dose_oral) * 100.

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8
Q

What is the significance of absolute bioavailability?

A

It compares the bioavailability of a drug given via an extravascular route to its IV administration.

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9
Q

What is relative bioavailability?

A

The comparison of bioavailability between two different formulations of the same drug.

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10
Q

How is relative bioavailability calculated?

A

F_rel = (AUC_test / AUC_standard) * (Dose_standard / Dose_test) * 100.

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11
Q

Why is relative bioavailability important?

A

It assesses formulation differences, e.g., comparing a new oral tablet with an existing oral solution.

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12
Q

What does bioequivalence mean?

A

Two drug products have no significant difference in rate and extent of absorption when given at the same molar dose under similar conditions.

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13
Q

What parameters are used to assess bioequivalence?

A

AUC, C_max (maximum concentration), and T_max (time to reach maximum concentration).

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14
Q

What is the acceptable range for bioequivalence studies?

A

AUC and C_max must be between 80%-125% of the reference product.

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15
Q

Why are bioequivalence studies required for generic drugs?

A

To ensure they have the same efficacy and safety profile as the branded drug.

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16
Q

How do formulation changes impact bioavailability?

A

Variations in excipients, particle size, or manufacturing can alter drug absorption and lead to toxicity or reduced efficacy.

17
Q

How does route of administration affect bioavailability?

A

IV > IM/SC/TD > Rectal > Oral > Topical (PROT mnemonic: Parenteral > Rectal > Oral > Topical).

18
Q

What is the salt factor (S), and why is it important?

A

The fraction of the free drug present in a salt or ester form, impacting dosing calculations.

19
Q

How is the salt factor used in dose calculations?

A

Dose_salt = Dose_free / S.

20
Q

How does first-pass metabolism impact oral bioavailability?

A

It reduces bioavailability as the drug is metabolized before reaching systemic circulation.

21
Q

What are examples of drugs with significant first-pass metabolism?

A

Propranolol, morphine, and nitroglycerin.

22
Q

What factors impact oral drug absorption?

A

Gastric pH, gastric emptying, enzymatic degradation, and interactions with food or other drugs.

23
Q

Why do modified-release formulations require separate bioavailability studies?

A

Their altered drug release profiles can significantly affect absorption and systemic exposure.

24
Q

What is the difference between an innovator drug and a generic drug?

A

The innovator drug is the original patented product; generics must demonstrate bioequivalence but may differ in excipients and manufacturing sites.

25
Q

What is the significance of C_max and T_max in bioavailability studies?

A

C_max represents peak drug concentration; T_max indicates the time taken to reach peak concentration, both affecting drug efficacy and safety.