Topic 12: Medicinal Chemistry Flashcards
Define “drug”
a substance that affects how the body works. Could be for better or worse
Define “medicine”
a substance that improves health. These could be natural or synthetic. Synthetic could contain other non-active ingredients to help administration of the medicine
What are three possible effects of a drug or medicine?
alters incoming sensory sensations, alters mood/emotions, alters physiological state
Four methods of administering drugs?
oral, inhalation, rectal, parenteral (injection)
What are three types of parenteral (injection) drug administrations?
intramuscular, subcutaneous (injected under skin), intravenous (most rapid effect as drug enters bloodstream directly)
What is the lethal dose?
The dose that causes death in 50% of the animal population
What is the effective dose?
The dose that causes noticeable effect in 50% of the animal population
What is therapeutic index?
Ratio of lethal/toxic dose to effective dose
How do you calculate therapeutic index for humans?
TD50/ED50 (Toxic dose/effective dose)
How do you calculate therapeutic index for animals?
LD50/ED50
What is therapeutic window?
Range of dosages between the minimum amounts of the drug that produce the desired effect and a medically adverse effect
What is drug tolerance? What can it lead to?
It occurs as the body adapts to the action of the drug, so a person needs larger doses to achieve the same effect. It can lead to addiction
What is bioavailability?
The fraction of the administered dosage that actually reaches the target part of the human body
What are three factors affecting bioavailability?
solubility, administration method, functional group
What are analgesics?
Painkiller drugs
What do prostglandins do?
When cells are damaged, they release prostglandins with stimulate pain receptors in the body, which send nerve messages to the brain, causing it to feel pain. Prostglandins also dilate blood vessels near an injury, leading to swelling and increased pain as part of the inflammatory response.
How do analgesics work?
They block the pathway between the injury and pain receptors. They prevent the nerves at the injury from being stimulated and prevent prostglandins from being released, thereby relieving pain and inflammation.
Mild analgesics do not alter brain function, so they are known as…
non narcotic
What is an antipyretic?
A fever-reducing drug
What is the chemical reaction for the synthesis of aspirin?
salicylic acid + ethanoic anhydride —> aspirin and ethanoic acid
After the first reaction is complete, how is aspirin produced?
The aspirin product is recrystallized from hot water to obtain aspirin
How can you confirm the purity of aspirin?
By its melting point. Impurities lower the melting point. Pure aspirin melts at 138-140 C.
Also through infrared spectrum. It has a peak at 1750 and 1680 because of the two C=O bonds, and very broad absorption between 2500-3500 due to carboxylic acid
How can aspirin be made more soluble?
Aspirin is slightly polar but not very soluble in water. By reacting it with sodium hydroxide to form an ionic salt, it becomes more soluble. Once it reaches a strongly acidic environment like the stomach, it becomes un-ionized.
Aspirin in the form of ionic salt is also called…
soluble/dispersible aspirin
How can the side effects of aspirin be reduced?
Coatings and buffers can delay activity until the small intestine to reduce side effects
What are the physiological effects of aspirin?
Anticoagulant: reduces blood’s clotting ability. Can cause irritation and ulceration of the stomach.
What is synergy?
The phenomenon in which the effects of a medicine/drug are more acute when drinking alcohol. With aspirin, a person should not be drinking to avoid ulcers and bleeding in the stomach
How does penicillin work?
It has a ring attached to the molecule called beta-lactam, which has one N atom and 3 C atoms. The ring is easily broken due to strained bonds. Beta-lactam binds near the active site of transpeptidase and breaks off of the penicillin molecule, preventing transpeptidase from working. Transpeptidase is the enzyme that helps bacteria build cell walls. Without a cell wall, the bacterium dies.
What are a few disadvantages of penicillin?
Many people have penicillin allergies. Also, penicillin G is broken down in the stomach, so it is often most effective when injected into the blood or taken as a pill.
How does antibiotic resistance to penicillin form?
When penicillin or other antibiotics are overprescribed, the bacteria with penicillinase are able to multiply because of less competition. Penicillinase (aka beta-lactamase) is an enzyme that breaks the beta-lactam ring and deactivates it, rendering the penicillin ineffective. Resistance can also develop because some livestock are given antibiotics, which humans then consume.
How have people combatted resistance to penicillin?
Development of methicillin and oxacillin; legislation to prevent over-prescription of penicillin; patient education
How do strong analgesics work?
They temporarily interact with the receptor sites in the brain without depressing the central nervous system, causing the pain signals in the brain and spinal cord to be blocked.
What are some examples of strong analgesics?
Morphine, opiates like heroin, codeine, demerol
Why are opiates supposed to be strictly controlled?
They are all addictive and can lead to tolerance.
Heroin is also called…
diamorphine
What are 7 short term effects of strong analgesics?
Euphoria, dulling pain, depress nervous system, slow breathing and heart rate, cough reflex inhibited, nausea and vomiting, coma/death in high doses
What are 6 long term effects of strong analgesics?
Constipation, loss of sex drive, disruption of menstrual cycle, poor eating habits, risk of AIDS, hepatitis, etc. thru shared needles, social problems like theft and prostitution
When do withdrawal symptoms start for addicts? What can these include?
6-24 hrs after stopping the drug. Hot/cold sweats, diarrhea, anxiety, cramps
What is one treatment to wean addicts off of their addiction?
Methadone as a heroin replacement. It is an amine, functions as an analgesic, does not produce euphoria
Why is diamorphine much more potent than morphine?
Morphine contains two polar hydroxyl (OH) groups. When morphine is converted to heroin to form the diester, the OH groups are replaced by much less polar ethanoate groups. Therefore heroin is much more soluble in non-polar lipids, allowing it to rapidly penetrate the lipid-based blood-brain barrier and reach the brain in higher concentrations than morphine.
How can morphine and heroin be converted into ionic salts?
They contain a tertiary amine group and can be reacted with hydrochloric acid to form ionic salts.
How can converting heroin into an ionic salt be useful for pain treatment?
For extreme pain after surgery or during cancer, diamorphine in the form of diamorphine hydrochloride is often injected to increase its bioavailability.
What are the two main ways in which antiviral drugs work?
By altering cell’s genetic material so that the virus cannot use it to multiply, or by blocking enzyme activity in the host cell so that the virus either cannot multiply or is prevented from leaving teh cell.
What is the difference between viruses and bacteria?
Viruses are not technically alive. They only have DNA or RNA and protein, no cell structure, and require a host to multiply. Bacteria are single-celled organisms that do not need a host to survive.
Why is it so hard to develop antiviral drugs?
Viruses are constantly mutating and multiplying
What is a drug (starting with “T”) that is effective against influenza A and B? How does it work?
oseltamivir aka Tamiflu. It inhibits the active site of neuraminidase, the enzyme that the virus uses to stick to the host cell wall.
What is another drug, starting with R, that combats the flu? How is it different from Tamiflu?
zanamivir aka Relenza. It has many polar hydroxyl and amine groups, along with a carboxylic acid group, that make it more soluble in polar solvents than Tamiflu.
What is AIDS? What kind of virus is it?
It is a retrovirus (RNA, not DNA) that is caused by HIV. It causes failure of the immune system, making the body much more susceptible to infections
How does HIV reproduce?
It infects CD4 T cells (white blood cells). It releases its RNA into the host cell and the enzyme reverse transcriptase causes the RNA to turn into viral DNA. This integrates into the cell’s DNA and replicates with it when the cell divides. When the cell dies, the viral particles are released in large amounts.
Why is HIV/AIDS so hard to defeat?
It destroys helper T cells, which should be defending the body against the virus
It mutates very quickly, so it escapes the immune response
It is often dormant in the host cells so the immune system has nothing to respond to
What are ARVs? What do they do for patients with HIV?
They are antiretroviral drugs. They do not cure but rather suppress the HIV infection, so HIV can be considered chronic, not terminal, and it can help prevent a mother from giving to a future child.
What four stages of the HIV cycle do ARVs interrupt?
binding the virus to cell receptor
reverse transcription of RNA to DNA (most common)
integration of DNA into host chromosome
release of new viral particles
What is a limitation of ARVs?
The treatments need to be sustained for life with a combination for effectiveness. Very expensive.
Is there an HIV/AIDS vaccine?
No. There is treatment for those with HIV, but no vaccine for those without it
What are the two types of radioactive waste?
High level waste (HLW) and low level waste (LLW)
What is the difference between HLW and LLW?
LLW is items like gloves, paper towels, etc. that have handled radioactive materials. Activity level is low, and half-lives are short. HLW has high activity and long half-lives.
How are HLW and LLW disposed of?
HLW is vitrified (turned into a glass-like material) and stored underground in concrete bunkers. LLW is disposed of in landfill or in the sea.
What kind of isotopes are generally used for radioisotope therapy?
iodine 131, strontium 89, samarium 153
Where does antibiotic waste come from?
Urine of people taking antibiotics and from animals who are fed antibiotics. This often makes its way to the rivers.
Why is antibiotic waste an issue?
Microogranisms in water or soil take up the waste and can become resistant to the antibiotics. If these bacteria enter water or food, the antibiotics can become inneffective.
How are solvents used in drug production disposed of?
Separated into solvents with and without chlorine. Chlorinated solvents must be incinerated at high temperatures to prevent formation of carcinogenic dioxins. Nonchlorinated solvents may be recycled, burned, or disposed of in rivers or the sea
What is green chemistry?
Safe disposal is important but green chemistry aims to minimize the use and creation of hazardous substances in the first place, thereby reducing pollution at its source and conserving resources.
What are three factors in creating new drugs safely?
Aiming for high atom economy and low environmental factor. Keeping the number of steps in synthesis to a minimum. Using greener, safer solvents/reactants.
What is atom economy?
ratio of total mass of desired product to total mass of all products, essentially measuring how much reactant remains in the final product
What is environmental factor (E-factor)?
the mass of total waste over mass of product. total waste (kg) / product (kg)
What is carbon efficiency?
amount of carbon in product / total amount of carbon in reactants
Why is it important to minimize the number of steps in synthesis?
More steps means more waste.
Why is it important to use safer solvents and reactants?
They are part of the many steps of synthesis. They can be carcinogenic.
Give an example of green chemistry in practice.
Tamiflu: more and more streamlined ways of synthesizing tamiflu have been developed, each more sustainable.
What are antacids? When are they most effective and why?
Bases like metal oxides, hydroxides, carbonates, hydrogencarbonates. They are used to reduce excess stomach acid and are best when taken one to three hours after eating because food can remain in the stomach for up to four hours after eating
How do antacids work?
They neutralize acid, preventing inflammation, relieving pain and discomfort, allowing the stomach lining and mucus layer to mend.
How do antacids treat ulcers?
They prevent acid from attacking the damaged stomach lining, allowing the ulcer to heal.
What are two antacid reactions using NaHCO3 and Na2CO3 as the antacids?
NaHCO3 + HCl —> NaCl + CO2 + H2O
Na2CO3 + HCl —> 2 NaCl + CO2 + H2O
What are two antacid reactions using Mg(OH)2 and Al(OH)3?
Mg(OH)2 + HCl —> MgCl2 + 2 H2O
Al(OH)3 + HCl —> AlCl3 + 3 H2O
How do you determine which antacid will be the most effective for a given mass?
Convert the g to mol of each antacid. Use mole ratios to determine how much HCl will be neutralized by each antacid.
What are side effects of antacids?
Belching, diarrhea, constipation.
What are active metabolites?
The active form of a drug after it has been processed by the body
What are side effects of rantidine?
Diarrhea, headache, dizziness. Long term use can lead to risk of osteoporosis and food/drug allergies
What are the gastric juices inside the stomach?
Hydrochloric acid (stomach acid), mucus and pepsinogen (turns into an enzyme for breaking down proteins)
What are H2-receptor antagonists?
Drugs used to block the action of histamine on the histamine H2-receptors of parietal cells, thereby inhibiting acid production
What is histamine?
A substance secreted by certain cells that then stimulates acid-making cells in the stomach lining
What is an example of an H2-receptor antagonist?
ranitidine (Zantec)
What are PPIs?
Proton pump inhibitors: another class of drug used to suppress acid secretion in the stomach. They can also help reduce acid-reflux symptoms like heartburn
How do PPIs work?
They cause a long-lasting reduction of gastric acid production and work by interacting with a chemical system called the proton pump found in the parietal cells in the stomach lining that make the acid. They thereby inhibit the ability of these cells to secrete acid and help ulcers heal or prevent them from forming.
What are two examples of PPIs?
omeprazole (Prilosec) and esomeprazole (Nexium)
Why are buffer solutions important?
Buffer solutions resist pH changes in the body when small amounts of acids or alkali are added to them, thereby maintaining the pH of the body within strict limits so that enzymes function correctly
How is an acidic buffer solution made?
Mixing a weak acid together with a salt of that acid and a strong base. The weak acid is only slightly dissociated, but the salt is fully dissociated
How does an acidic buffer prevent pH fluctuation if acid is added?
If acid is added to the buffer, the extra H+ ions from the acid are removed as they combine with the salt ions to form undissociated acid, so the concentration of H+ ions remains unaltered.
How does an acidic buffer prevent pH fluctuation if a base is added?
If an alkali is added, the hydroxide ions from the alkali are removed by their reaction with the undissociated acid to form water, so the H+ concentration stays the same.
How is an alkali buffer formed?
An alkali buffer w/ fixed pH greater than 7 can be made from a weak base plus the salt of that base and a strong acid.
How does an alkali buffer work?
If H+ is added, it combines w/ OH- to form water. If OH- is added, it combines w/ the base to form an undissociated base
What is Ka, and how do you calculate it?
Ka is the equilibrium expression for acidic buffer solutions. It is calculated like so:
( [product A] * [product B] ) / ( [reactant A] * [reactant B] )
What is the Henderson Hasselbach equation?
pH = pKₐ + log([A⁻]/[HA]), in which pKa is -log(Ka), A- is conjugate base, HA is acid
What is rantidine?
An h2-receptor antagonist
