Drugs Revision Notes

A drug is any substance that, when introduced into the body, causes a change in the body's chemical processes. This means it can affect how cells function, how signals are transmitted, or how enzymes work. Drugs are not limited to medicines; they include any chemical that influences bodily functions.

For example, caffeine in coffee is a drug because it affects the nervous system by blocking certain receptors, leading to increased alertness. Similarly, alcohol alters brain chemistry, affecting mood and coordination.

• A drug changes chemical reactions or processes inside the body.
• It can be natural (like caffeine) or synthetic (like many medicines).
• Not all drugs are used for treatment; some are recreational or harmful.

The body relies on complex chemical reactions to maintain life, such as metabolism, nerve signalling, and hormone regulation. Drugs can modify these reactions by interacting with molecules like enzymes or receptors.

For instance, some drugs bind to receptors on cells, either activating them (agonists) or blocking them (antagonists). This changes the normal chemical signalling pathways.

An example is morphine, which binds to opioid receptors in the brain to reduce pain perception by altering neurotransmitter release.

• Drugs interact with enzymes or receptors to change chemical reactions.
• They can increase or decrease the activity of biological molecules.
• This interaction leads to changes in physiological functions.

Drugs can be classified by their purpose or effect on the body. Therapeutic drugs are used to treat or prevent diseases, such as antibiotics that kill bacteria or insulin that regulates blood sugar.

Recreational drugs are taken for pleasure or altered states of consciousness, like nicotine or cannabis. Some drugs can have both therapeutic and harmful effects depending on use and dosage.

Understanding these categories helps in recognising the potential benefits and risks associated with drug use.

• Therapeutic drugs treat or prevent illness.
• Recreational drugs alter mood or perception.
• Some drugs have side effects or potential for abuse.

Knowing how drugs affect chemical processes is crucial for safe and effective use. Incorrect use can lead to harmful side effects or drug interactions.

For example, taking too much paracetamol can damage the liver because it overwhelms the body's ability to process it safely.

Healthcare professionals must understand drug actions to prescribe correct dosages and avoid adverse effects.

• Proper drug use ensures therapeutic benefits.
• Misuse can cause harmful side effects.
• Knowledge of drug effects supports safe medical practice.

Antibiotics are chemical substances used as medicines to treat infections caused by bacteria. They do not work against viruses or other types of pathogens. Antibiotics can be naturally derived from microorganisms or synthetically produced in laboratories.

Their main purpose is to either kill bacteria (bactericidal effect) or stop bacteria from multiplying (bacteriostatic effect), allowing the body's immune system to eliminate the infection.

• Antibiotics target bacteria specifically, not viruses.
• They can kill bacteria or inhibit their growth.

Different antibiotics work by interfering with restorative processes in bacterial cells. For example, some antibiotics prevent bacteria from building their cell walls, which are essential for their survival. Without a proper cell wall, bacteria burst and die.

Other antibiotics inhibit protein synthesis by binding to bacterial ribosomes, stopping bacteria from producing proteins needed for growth and reproduction. Some antibiotics interfere with bacterial DNA replication, preventing bacteria from multiplying.

Because human cells do not have cell walls and have different ribosomes, antibiotics can target bacteria without harming human cells directly.

• Disrupting bacterial cell wall synthesis causes bacteria to die.
• Inhibiting protein synthesis stops bacterial growth.
• Interfering with DNA replication prevents bacterial multiplication.

It is important to use the correct antibiotic for the specific type of bacterial infection. Different bacteria may be sensitive to different antibiotics, so doctors often identify the bacteria before prescribing treatment.

Taking the full course of antibiotics as prescribed ensures that all bacteria are killed or inhibited, reducing the chance of the infection returning or bacteria developing resistance.

Incorrect use, such as stopping treatment early or using antibiotics for viral infections, can lead to ineffective treatment and promote antibiotic resistance.

• Matching antibiotic to bacteria type improves treatment success.
• Completing the full course prevents survival of resistant bacteria.
• Avoid using antibiotics for viral infections.

For example, penicillin is an antibiotic that kills bacteria by preventing them from forming cell walls. It is effective against many common bacterial infections like strep throat.

Another example is tetracycline, which inhibits protein synthesis in bacteria, stopping their growth. It is used to treat infections such as acne or urinary tract infections.

These examples show how different antibiotics target bacteria in different ways to treat infections effectively.

• Penicillin kills bacteria by disrupting cell walls.
• Tetracycline stops bacterial growth by inhibiting protein synthesis.

Overusing or misusing antibiotics can lead to bacteria evolving resistance, meaning the antibiotics become less effective or ineffective. Resistant bacteria can cause infections that are harder to treat and may require stronger or more toxic drugs.

To prevent this, antibiotics should only be used when necessary and prescribed by a healthcare professional. Avoid sharing antibiotics or using leftover medication.

This responsible use helps preserve the effectiveness of antibiotics for future patients.

• Antibiotic resistance arises from misuse and overuse.
• Only use antibiotics when prescribed by a doctor.
• Complete the prescribed course to prevent resistance.

Antibiotics are medicines designed to kill bacteria or stop their growth. They target specific bacterial structures or processes, such as cell wall synthesis or protein production, which are essential for bacterial survival. For example, penicillin interferes with the formation of bacterial cell walls, causing bacteria to burst and die.

• Antibiotics target bacteria, not viruses.
• They disrupt vital bacterial functions to kill or inhibit bacteria.

Some bacteria can survive antibiotic treatment by developing resistance. This happens when bacteria undergo genetic changes, such as mutations or acquiring resistance genes from other bacteria. These changes may allow bacteria to produce enzymes that destroy the antibiotic, alter the antibiotic's target site, or pump the antibiotic out of the cell.

For instance, some bacteria produce an enzyme called beta-lactamase that breaks down penicillin, rendering it ineffective.

• Resistance arises through genetic mutations or gene transfer.
• Mechanisms include enzyme production, target modification, and efflux pumps.

When bacteria become resistant, antibiotics no longer work effectively, making infections harder to treat. This can lead to longer illness duration, increased risk of complications, and higher healthcare costs.

For example, methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria resistant to many antibiotics, causing difficult-to-treat infections in hospitals.

• Resistance reduces antibiotic effectiveness.
• Leads to more severe or prolonged infections.
• Increases healthcare challenges and costs.

Overusing or misusing antibiotics accelerates the development of resistance. Taking antibiotics when not needed, not completing prescribed courses, or using incorrect doses allows some bacteria to survive and develop resistance.

For example, using antibiotics to treat viral infections like the common cold is ineffective and promotes resistance.

• Overuse and misuse of antibiotics promote resistance.
• Incomplete treatment courses allow resistant bacteria to survive.

To limit resistance, antibiotics should be used only when necessary and exactly as prescribed. Healthcare providers and patients must follow guidelines to reduce unnecessary antibiotic exposure.

Good hygiene and infection control also help prevent the spread of resistant bacteria.

For example, handwashing in hospitals reduces transmission of resistant bacteria like MRSA.

• Use antibiotics only when prescribed.
• Complete the full course of treatment.
• Practice good hygiene to prevent infection spread.

Bacteria are single-celled living organisms that can reproduce independently. They have cellular structures such as cell walls and can carry out metabolic processes. Viruses, in contrast, are much smaller and are not cells; they consist of genetic material (DNA or RNA) enclosed in a protein coat and require a host cell to reproduce.

Because bacteria are living cells, they can be targeted by drugs that interfere with their cellular functions. Viruses rely on host cells to replicate, so drugs must target viral replication mechanisms without harming the host cells.

• Bacteria are living cells; viruses are non-living particles.
• Bacteria reproduce independently; viruses need host cells.
• Structural differences determine drug effectiveness.

Antibiotics are substances that kill bacteria or inhibit their growth. They achieve this by targeting specific bacterial features such as cell wall synthesis, protein production, or DNA replication. For example, penicillin interferes with the formation of bacterial cell walls, causing bacteria to burst.

By disrupting essential bacterial processes, antibiotics reduce bacterial populations, allowing the immune system to clear the infection.

• Antibiotics target bacterial cell structures or functions.
• They can be bactericidal (kill bacteria) or bacteriostatic (stop growth).
• Example: Penicillin inhibits bacterial cell wall synthesis.

Viruses lack the cellular structures that antibiotics target. Since viruses replicate inside host cells, antibiotics cannot reach or affect the viral replication machinery without damaging the host cells.

Treating viral infections requires antiviral drugs that specifically interfere with viral replication or boost the immune response.

• Viruses have no cell walls or metabolic pathways targeted by antibiotics.
• Antibiotics cannot penetrate or affect viruses inside host cells.
• Antiviral medications are needed for viral infections.

Using antibiotics to treat viral infections is ineffective and can contribute to antibiotic resistance. Resistance occurs when bacteria evolve mechanisms to survive antibiotic exposure, making infections harder to treat.

For example, prescribing antibiotics for the common cold, which is viral, offers no benefit and promotes resistance development.

Appropriate use of antibiotics preserves their effectiveness for bacterial infections.

• Antibiotic misuse promotes resistant bacteria.
• Resistance leads to harder-to-treat infections.
• Only use antibiotics for confirmed bacterial infections.

Recognising that antibiotics only work against bacteria helps ensure correct treatment choices. For instance, a sore throat caused by bacteria may require antibiotics, but one caused by a virus will not.

Healthcare professionals must diagnose infections accurately and prescribe antibiotics only when necessary to prevent resistance and protect public health.

• Antibiotics are ineffective against viruses.
• Correct diagnosis guides appropriate treatment.
• Responsible antibiotic use prevents resistance.

Antibiotics are drugs used to kill or inhibit bacteria causing infections. However, bacteria can undergo genetic changes that make them less affected or unaffected by antibiotics. This process is called antibiotic resistance.

Resistance arises because bacteria reproduce rapidly and can mutate randomly. Some mutations may enable bacteria to survive antibiotic exposure. When antibiotics are used, sensitive bacteria die, but resistant ones survive and multiply, leading to a resistant population.

For example, if a patient takes antibiotics unnecessarily or does not complete a prescribed course, some bacteria may survive and develop resistance. These resistant bacteria can then spread to others, making infections harder to treat.

• Bacteria reproduce quickly, allowing mutations to occur.
• Mutations can confer resistance to antibiotics.
• Antibiotic use kills sensitive bacteria but selects for resistant ones.
• Incomplete or unnecessary antibiotic use encourages resistance.

Overusing antibiotics means using them when they are not needed, such as for viral infections, or using them excessively in agriculture and animal farming. This widespread use increases the chances that bacteria will encounter antibiotics and develop resistance.

One well-known resistant bacterium is MRSA (Methicillin-resistant Staphylococcus aureus), which is resistant to many common antibiotics. MRSA infections are difficult to treat and can cause serious illness or death.

Overuse also reduces the effectiveness of antibiotics for everyone, as resistant bacteria spread in the community and hospitals. This threatens the ability to treat common infections and perform medical procedures safely.

• Antibiotics do not work against viruses but are sometimes misused for viral infections.
• Excessive antibiotic use in humans and animals promotes resistance.
• MRSA is an example of a dangerous resistant bacterium.
• Resistance leads to longer illnesses, higher medical costs, and increased mortality.

To prevent resistance, antibiotics should only be prescribed when there is a confirmed bacterial infection that requires treatment. Doctors use diagnostic tests and clinical judgement to decide if antibiotics are necessary.

Patients should follow the prescribed dosage and complete the full course to ensure all bacteria are killed, reducing the chance of survivors developing resistance.

In agriculture, limiting antibiotic use to therapeutic purposes rather than growth promotion helps reduce resistance development.

• Prescribe antibiotics only for confirmed bacterial infections.
• Complete the full prescribed antibiotic course.
• Avoid using antibiotics for viral infections.
• Restrict antibiotic use in farming to necessary treatments.

By reducing unnecessary antibiotic exposure, fewer bacteria are exposed to selective pressure that encourages resistance. This slows down the evolution and spread of resistant strains like MRSA.

When antibiotics are used responsibly, sensitive bacteria remain dominant, and resistant bacteria have less opportunity to multiply and spread.

This approach preserves the effectiveness of current antibiotics, ensuring they remain useful for treating infections in the future.

• Less antibiotic use means less selective pressure for resistance.
• Sensitive bacteria outcompete resistant ones when antibiotics are limited.
• Preserving antibiotic effectiveness protects future treatment options.

Antibiotic resistance is a global health threat. Resistant infections cause longer hospital stays, more complicated treatments, and increased mortality.

Public health campaigns promote awareness about responsible antibiotic use among healthcare providers and the public.

Monitoring antibiotic prescriptions and resistance patterns helps guide policies to reduce resistance emergence.

• Resistant infections increase healthcare burden and costs.
• Education on antibiotic stewardship is vital.
• Surveillance informs effective antibiotic policies.