Bioprecursor Prodrugs Quiz
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Questions and Answers

What is the primary purpose of using sentry drugs?

  • To assist or enhance the effects of the primary drug (correct)
  • To monitor drug levels in the bloodstream
  • To replace the primary drug completely
  • To create new therapeutic drugs

What role does clavulanic acid play in relation to penicillins?

  • It enhances the absorption of penicillins
  • It inhibits an enzyme that deactivates penicillins (correct)
  • It increases the excretion rate of penicillins
  • It acts as a replacement for penicillins

How does uracil enhance the effectiveness of Tegafur in chemotherapy?

  • By converting Tegafur into a more potent drug
  • By speeding up the metabolic rate of Tegafur
  • By inhibiting the enzyme that metabolizes 5-fluorouracil (correct)
  • By increasing drug resistance in cancer cells

In the combination of Kaletra, what is the function of ritonavir?

<p>To inhibit the enzyme that degrades lopinavir (B)</p> Signup and view all the answers

What is a prodrug, as exemplified by Tegafur?

<p>A drug that has no effect until metabolized (B)</p> Signup and view all the answers

What is the primary requirement for antimetabolites that are nitrogenous base analogues to exert their effects?

<p>They need to be converted into a triphosphate derivative. (A)</p> Signup and view all the answers

Which enzyme is specifically involved in the conversion of 6-Mercaptopurine to its active form?

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

What is the action of 5-Fluorouracil once it is activated into its corresponding deoxyribonucleotide?

<p>It inhibits thymidylate synthetase. (A)</p> Signup and view all the answers

Which of the following drugs also functions similarly to 5-Fluorouracil and 6-Mercaptopurine in terms of requiring activation?

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

The mechanism involving antimetabolites typically targets which cellular synthesis process?

<p>De novo purine synthesis (B)</p> Signup and view all the answers

What is the primary reason large doses of levodopa are required for effective treatment?

<p>It rapidly metabolizes into dopamine before entering the CNS. (B)</p> Signup and view all the answers

Why does carbidopa itself not affect levodopa conversion in the brain?

<p>It cannot pass through the blood-brain barrier. (D)</p> Signup and view all the answers

What role does adrenaline play when combined with local anesthetics?

<p>It constricts blood vessels to minimize the anesthetic's distribution. (B)</p> Signup and view all the answers

How does metoclopramide assist in the treatment of migraines when used with analgesics?

<p>It increases gastric motility for faster absorption of the analgesic. (C)</p> Signup and view all the answers

What side effects may result from high doses of levodopa?

<p>Nausea and vomiting. (C)</p> Signup and view all the answers

What defines a bioprecursor prodrug?

<p>Compounds that owe their activity to oxidative or reductive metabolic products. (A)</p> Signup and view all the answers

Which of the following is an example of a bioprecursor prodrug and its activation mechanism?

<p>Cyclophosphamide; metabolized to phosphoramide mustard. (D)</p> Signup and view all the answers

What was significant about prontosil in the context of bioprecursor prodrugs?

<p>It acted as an antibacterial agent only after being metabolized to sulfanilamide. (C)</p> Signup and view all the answers

Which of the following statements regarding activation mechanisms of bioprecursor prodrugs is true?

<p>Oxidation and reduction are common activation mechanisms. (D)</p> Signup and view all the answers

Which of the following prodrugs is activated by an azo reductase enzyme?

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

What characterizes a mutual prodrug?

<p>It is made of two pharmacologically active agents that enhance each other's activity. (B)</p> Signup and view all the answers

Which statement about sultamicillin is true?

<p>It combines ampicillin with a β-lactamase inhibitor. (D)</p> Signup and view all the answers

What is the primary challenge faced by ampicillin when used alone?

<p>Resistance from bacteria due to high levels of β-lactamase enzymes. (D)</p> Signup and view all the answers

Why are mutual prodrugs like sultamicillin beneficial in treating infections?

<p>They facilitate the simultaneous release of two active compounds that work synergistically. (D)</p> Signup and view all the answers

What is a key requirement for the components of an ideal mutual prodrug?

<p>Their absorption, distribution, and elimination profiles should be similar. (C)</p> Signup and view all the answers

What is the primary role of Levodopa in the treatment of Parkinson's disease?

<p>It is a prodrug that generates dopamine in the brain. (C)</p> Signup and view all the answers

Why can't dopamine be directly used in therapies for Parkinson's disease?

<p>It is too polar to effectively cross the blood-brain barrier. (A)</p> Signup and view all the answers

What modification do GABA analogs undergo to enhance their effectiveness as anticonvulsants?

<p>Enhancing their lipophilicity to cross the blood-brain barrier. (C)</p> Signup and view all the answers

What mechanism enables Levodopa to cross cell membranes?

<p>It mimics a natural amino acid, utilizing transport proteins. (A)</p> Signup and view all the answers

The effectiveness of GABA analogs in treating epilepsy is primarily due to their ability to:

<p>Cross the blood-brain barrier and release GABA in the brain. (A)</p> Signup and view all the answers

What is the primary reason Sulindac is considered a prodrug?

<p>It requires metabolic conversion to become pharmacologically active. (B)</p> Signup and view all the answers

What is the significance of the lipophilicity of Sulindac sulfide compared to Sulindac?

<p>It leads to a higher concentration inside the cell. (B)</p> Signup and view all the answers

Which of the following describes the first step in the bioactivation of Cyclophosphamide?

<p>Hydrolysis to form a carbinolamine. (A)</p> Signup and view all the answers

What is a major toxic metabolite formed during the activation of Cyclophosphamide?

<p>Acrolein. (D)</p> Signup and view all the answers

What is the role of the 4° Aziridinium ion in the bioactivation of Cyclophosphamide?

<p>It is a highly reactive alkylating intermediate responsible for cytotoxicity. (C)</p> Signup and view all the answers

What is the pKa value of phosphoramide mustard?

<p>4.75 (B)</p> Signup and view all the answers

Which statement about Sulindac's action mechanism is correct?

<p>It is reduced to a more potent sulfide metabolite. (A)</p> Signup and view all the answers

What differentiates Sulindac from Cyclophosphamide in terms of activation?

<p>Cyclophosphamide requires oxidative mechanisms for activation. (A)</p> Signup and view all the answers

What is the primary active component that Sulfasalazine gets converted into for its therapeutic effects in inflammatory bowel disease?

<p>5-Aminosalicylic acid (B)</p> Signup and view all the answers

Which statement accurately describes the pharmacokinetics of Sulfasalazine?

<p>It is poorly absorbed and mainly acts on the distal bowel. (B)</p> Signup and view all the answers

What is the mechanism by which Prednimustine becomes cytotoxic?

<p>It undergoes hydrolysis by serum esterases. (C)</p> Signup and view all the answers

What therapeutic use is associated with Prednimustine?

<p>Management of chronic lymphatic leukaemia and non-Hodgkin's lymphomas (A)</p> Signup and view all the answers

What property does the esterification of NSAIDs, like Benorylate, significantly affect?

<p>Suppresses gastric ulcerogenic activity (B)</p> Signup and view all the answers

What is the primary mechanism by which Clopidogrel and Prasugrel exert their effect on platelet aggregation?

<p>They irreversibly bind to the P2Y12 receptor. (D)</p> Signup and view all the answers

Which of the following statements accurately describes the metabolic activation of Primidone?

<p>It requires N-Oxidation metabolic activation. (D)</p> Signup and view all the answers

Why does Pro-2-PAM readily enter the central nervous system (CNS)?

<p>It is uncharged and hydrophilic, facilitating uptake. (C)</p> Signup and view all the answers

What is the effect of Clopidogrel and Prasugrel lasting for 7-10 days after discontinuation?

<p>Prevents reactivation of platelet aggregation. (C)</p> Signup and view all the answers

Which of the following best describes the relationship between 2-PAM and its prodrug form?

<p>The charge of 2-PAM restricts its transfer from the CNS. (A)</p> Signup and view all the answers

Flashcards

Sentry Drug

A drug that enhances another drug's effectiveness by inhibiting the enzymes that metabolize it.

Clavulanate Acid's Function

Inhibits beta-lactamase, preserving penicillin's antibiotic action.

Kaletra's Mechanism

Ritonavir in Kaletra inhibits CYP3A4, keeping lopinavir levels high for AIDS treatment.

Prodrug

A drug that needs to be changed by the body to become active.

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Tegafur-Uracil Combination

Tegafur, a prodrug of 5-FU, combines with Uracil to inhibite DPD, increasing 5-FU levels for cancer treatment.

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Antimetabolite activation

Antimetabolites, including analogues, require conversion to a triphosphate derivative to exert their effect.

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5-Fluorouracil activation

5-Fluorouracil needs conversion to a deoxyribonucleotide to hinder thymidylate synthase.

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6-Mercaptopurine activation

6-Mercaptopurine gets transformed to a ribonucleotide (triphosphate) to block purine synthesis.

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Phosphorylation in drug activation

Many drugs, like 6-Mercaptopurine and the others mentioned, require phosphorylation (adding a phosphate group) to become active.

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Key enzymes in drug activation

Enzymes like Phosphoribosyl transferase and HGPRT are crucial in converting drugs to their active forms.

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Bioprecursor Prodrug

A drug that is inactive until it's transformed by the body, typically through oxidation or reduction, into an active drug.

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Prontosil

An example of a bioprecursor prodrug that's inactive until converted by azo reductase into the active drug sulfanilamide.

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L-DOPA

A bioprecursor prodrug that gets converted into dopamine, a neurotransmitter important for movement and mood.

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How are bioprecursor prodrugs activated?

Bioprecursor prodrugs are activated typically through enzymatic reactions, like oxidation, reduction, or phosphorylation, to create an active drug molecule.

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What makes a bioprecursor prodrug different from a regular prodrug?

Bioprecursor prodrugs rely on oxidative or reductive activation, while regular prodrugs use hydrolysis reactions (like esterase or phosphorylation).

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Prodrug of Dopamine

A medication (like levodopa) that's converted to a more active form (dopamine) in the body.

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Levodopa Side Effect

Nausea and vomiting caused by dopamine buildup in the peripheral blood.

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Carbidopa's Role

Inhibits dopa decarboxylase, reducing peripheral dopamine production from levodopa.

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Blood-Brain Barrier

A protective barrier that prevents certain substances from entering the central nervous system (brain and spinal cord).

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Metoclopramide's Function

Increases gastric motility, leading to faster analgesic absorption and faster pain relief.

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Mutual Prodrug

A drug combination where each component enhances the other's activity, like a two-way synergy.

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What is Sultamicillin?

Sultamicillin is a combined drug containing ampicillin (antibiotic) and sulbactam (inhibitor of bacterial resistance enzymes).

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Ampicillin's Vulnerability

Ampicillin, a broad-spectrum antibiotic, can be ineffective against bacteria producing β-lactamase enzymes.

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Sulbactam's Role

Sulbactam is a β-lactamase inhibitor, inactivating enzymes that hinder ampicillin's effectiveness.

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Sultamicillin's Advantage

Sultamicillin overcomes bacterial resistance by combining ampicillin and sulbactam, making it useful for β-lactamase-producing infections.

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Levodopa: Why a Prodrug?

Levodopa is used to treat Parkinson's disease because it can cross the blood-brain barrier. It is converted to dopamine, a neurotransmitter deficient in Parkinson's.

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Blood-Brain Barrier Challenge

The blood-brain barrier prevents many molecules from entering the brain, including drugs that could treat brain disorders.

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Prodrugs for GABA

GABA, an inhibitory neurotransmitter, can't cross the blood-brain barrier effectively. Prodrugs like Progabide and Tolgabide are used to increase GABA levels in the brain and treat epilepsy.

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Dopamine Transport

Levodopa, a prodrug for dopamine, is recognized by amino acid transport proteins, allowing it to enter cells and eventually be converted to dopamine.

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Prodrug Mechanism

Prodrugs are inactive forms of drugs that are converted into their active form by the body. This allows them to more easily reach their target or avoid unwanted side effects.

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What is Sulindac?

Sulindac is a non-steroidal anti-inflammatory drug (NSAID) that acts as a prodrug. It is inactive on its own but transforms into a more potent and active form, Sulindac sulfide, through a reductive bioactivation process within the body.

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How does Sulindac activate?

Sulindac is reduced to Sulindac sulfide by undergoing a process called bioactivation. This reduction involves the gaining of electrons, specifically by a metabolic enzyme.

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Sulindac sulfide's location

Sulindac sulfide, the active form of Sulindac, is more lipophilic (fat-soluble) than Sulindac. This makes it readily penetrate cell membranes and accumulate inside cells.

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What is Cyclophosphamide?

Cyclophosphamide is a crucial anticancer drug that relies on oxidative bioactivation to become active. It undergoes a series of metabolic transformations to generate cytotoxic products that kill cancer cells.

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Cyclophosphamide Activation Step 1

Cyclophosphamide is first hydrolyzed, broken down by water, to form a carbinolamine. This molecule is then transported inside cells.

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Cyclophosphamide Activation: Key Intermediate

The highly reactive 4° Aziridinium ion is a major product of Cyclophosphamide's activation. This unstable ion plays a crucial role in alkylating DNA and damaging cancer cells.

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Phosphoramide Mustard

Phosphoramide mustard is a highly polar and cytotoxic metabolite of Cyclophosphamide. It gets trapped inside cells and contributes to the drug's anti-cancer effects.

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pKa of Phosphoramide Mustard

The pKa of Phosphoramide mustard is 4.75. This value indicates its acidity and influences how this active metabolite interacts with its cellular targets.

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Primidone: What is it?

Primidone is an anticonvulsant medication that belongs to the pyrimidinedione class of drugs. It's a prodrug, meaning it needs to be converted into its active form by the body before it can work.

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Primidone's Active Form?

The active form of primidone is phenobarbital, a well-known barbiturate.

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Pro-2-PAM: How does it work?

Pro-2-PAM is a prodrug that enters the brain easily. Once inside, it gets converted into 2-PAM, which is trapped inside the brain and helps reverse cholinesterase inhibitor poisoning.

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Clopidogrel & Prasugrel: What's their job?

Clopidogrel and prasugrel are medications that prevent blood clots by inhibiting platelet aggregation. They're prodrugs that need to be activated by the body.

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P2Y12 and Clopidogrel/Prasugrel

Clopidogrel and Prasugrel work by irreversibly binding to the P2Y12 receptor on platelets, preventing their activation and thus preventing blood clots.

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Sulfasalazine

A drug used for ulcerative colitis and regional enteritis. It's an azo dye pro-drug that gets converted into sulfapyridine and 5-aminosalicylic acid by intestinal bacteria.

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Benorylate

A prodrug that combines aspirin and paracetamol. It's an aryl ester of aspirin, meaning it's modified to reduce stomach irritation.

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Prednimustine

A prodrug containing prednisolone and the anti-cancer drug chlorambucil. It's activated by enzymes in the blood, releasing chlorambucil.

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How does Sulfasalazine work?

Sulfasalazine is absorbed poorly in the gut, so it primarily reaches the lower intestine, where it's broken down by bacteria into sulfapyridine (anti-bacterial) and 5-aminosalicylic acid (which fights bowel inflammation).

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What makes Benorylate unique?

Benorylate is a prodrug of aspirin and paracetamol, but its esterified form makes it less harsh on the stomach, compared to regular aspirin.

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Study Notes

Bioprecursor Prodrugs

  • Normal prodrugs rely on hydrolysis reactions for effectiveness.
  • Bioprecursor prodrugs use either oxidative or reductive activation to become active.
  • Bioprecursor prodrugs are inactive until activation.
  • The birth of bioprecursors occurred when the agent was demonstrated to be an actual drug.
  • Examples of bioprecursor prodrugs: Prontosil, sulfasalazine, cyclophosphamide, L-DOPA, chloroguanide, primidone, sulindac, and Pro-2-PAM.

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Test your knowledge on bioprecursor prodrugs, their mechanisms, and examples. Learn how these prodrugs differ from traditional ones and their activation processes. Explore the significance of bioprecursor prodrugs in pharmacology.

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