15. Halogen compounds
A section of Chemistry, 9701
Listing 10 of 284 questions
Drugs can be delivered in a number of ways. The method chosen depends both on the nature of the drug, and the problem it is being used to treat. Many common drugs are taken by mouth in forms similar to those shown. P Q digestible gel casing Some drugs are available in solution. How would the speed of action of this form compare with P and Q? Explain your answer. Explain which of the two forms, P or Q, would act the most rapidly when taken by mouth. Some drugs are broken down before they can be absorbed by the intestine. Suggest how the design of Q prevents this. After an abdominal operation drugs are often delivered by means of a ‘drip’ inserted into a blood vessel in the patient’s arm. Explain why this is more effective than taking painkillers by mouth. One of the molecules that has found a variety of uses in drug delivery is poly(ethylene glycol) or PEG. It is formed from dihydroxyethane, HOCH2CH2OH. 2n HOCH2CH2OH H–(OCH2CH2OCH2CH2)n–OH + (2n–1) H2O What type of reaction is this? Attaching a PEG molecule to a drug increases the time that it takes for the drug to be broken down and flushed from the body. There are thought to be two major reasons for this: firstly the PEG can form bonds to slow the passage of the drug around the body; secondly it may reduce the efficiency of breakdown of the drug by enzymes. What type of bonds would the PEG part of the molecule form with molecules in the body? Suggest why attaching a PEG molecule to a drug molecule would reduce the rate of the drug’s decomposition by enzymes. Drugs are often protein or polypeptide molecules. What type of reaction might occur in the breakdown of such a drug?
9701_w11_qp_43
THEORY
2011
Paper 4, Variant 3
View
Questions Discovered
284