Generics

What is AIDS?

Human Immunodeficiency Virus (HIV) is an RNA virus (known as a retrovirus) that specifically attacks the immune system, which affects your ability to fight other infections.  HIV infects CD4 cells, which are white blood cells that play an essential role in the immune response to infection.  Without treatment, the virus multiplies and spreads, and the amount of virus in your body increases, while at the same time, the number of CD4 cells decreases.  Eventually, the immune system becomes severely damaged and is unable to fight infection, leading to an increased risk of opportunistic infection, which is an infection that the body usually can fight when not immunocompromised.  This stage of HIV infection is called Acquired Immune Deficiency Syndrome (AIDS) and is potentially life-threatening. 

How do antiretrovirals work?

Antiretrovirals are used to treat HIV infection, and are designed to prevent the replication of the virus.  The aim of antiretroviral treatment is to reduce the amount of virus in the body (viral load) down to a low level and prevent the spread of HIV.  Antiretrovirals do not kill the virus.  Once HIV replication is reduced, the numbers of CD4 cells can increase, so that the immune system can recover, and further damage is prevented.  Antiretroviral therapy uses a combination of different drugs that work by attacking a different stage of the viral replication process.  Using a combination of drugs reduces the risk of the virus becoming resistant.  Some of these combination medications are supplied as a single tablet containing a fixed dose of two or three drugs.

Types of antiretroviral drugs include:

• Reverse transcriptase (RT) inhibitors.  RT is a virus-specific enzyme needed for HIV replication.  There are two types of RT inhibitor that work by different mechanisms:
  • nucleoside analogue reverse transcriptase inhibitor (NRTI), such as tenofovir and zidovudine
  • non-nucleoside reverse transcriptase inhibitor (NNRTI), such as efavirenz and nevirapine. 
• The viral protease enzyme is another drug target.  This enzyme is needed to allow the mature active virus to be released and infect new cells.  These drugs include ritonavir and indinavir.

What is depression?

Depression is not just feeling low, which we all feel from time to time.  It is a long term feeling of sadness that persists for more than a few weeks and affects your behaviour and quality of life.  Depression is an illness, which can range from mild to severe depending on your symptoms.  These symptoms include anxiety, loss of interest in your usual activities, disturbed sleep, change in appetite, fatigue, feelings of worthlessness or guilt, difficulty thinking or concentrating, and recurrent thoughts of suicide.  This condition is also called Major Depressive Disorder and is one of several mood disorder treated by antidepressants.  Other mood disorders include anxiety disorder, bipolar disorder, obsessive-compulsive disorder (OCD), panic disorder and post-traumatic stress disorder (PTSD).

Depression and other mood disorders are thought to be due to an imbalance of brain chemicals called neurotransmitters, particularly serotonin and noradrenaline.  These brain chemicals pass messages between nerve cells (neurones) in the area of the brain that regulates mood.  When a neurotransmitter is released by one neurone, it passes across the gap between neurones (synapse) and triggers an electrical impulse in the next neurone.  Transmission of a nerve signal from one neurone to another allows nerve cells to communicate with each other.  Any neurotransmitter remaining in the synapse after release from the first nerve cell (pre-synaptic) and not used by the receiving nerve cell (post-synaptic), is taken up back into the pre-synaptic neurone.  This process is called neurotransmitter reuptake.

How do antidepressants work?

Antidepressants are medications that are used to treat symptoms of depression and other mood disorders.  They are classed according to how they work and which brain chemicals they target.  These include:

• Selective serotonin reuptake inhibitors (SSRI) such as fluoxetine, escitalopram, and sertraline.
• Serotonin noradrenaline reuptake inhibitors (SNRI) such as venlafaxine.
• Tricyclic antidepressants, such as imipramine, and tetracyclic antidepressants such as trazodone, are non-selective neurotransmitter reuptake inhibitors as well as blocking effect of other neurotransmitters like histamine and acetylcholine.

Why is high cholesterol a health problem?

Cholesterol is a fat that is produced by the liver but also comes from our diet.  We all need some cholesterol for normal body functions, such as making cell membranes, producing and transporting hormones, and building protective nerve sheaths.  Eating a lot of fatty foods in your diet can increase your blood cholesterol levels above healthy levels.  Since cholesterol is not water-soluble, it circulates in the blood attached to proteins called lipoproteins.  Excess cholesterol is deposited in the arteries causing them to become blocked and hardened, which narrows the arteries and restricts blood flow.  This condition, called atherosclerosis, increases your risk of developing cardiovascular disease, including heart attack, angina, and stroke.

How do cholesterol-lowering medications work?

Cholesterol-lowering medications are used to reduce high cholesterol and triglyceride levels.  They are classed according to how they work and include:

• Statins that block the production of cholesterol by the liver but have no effect on dietary cholesterol, such as atorvastatin, simvastatin, and rosuvastatin
• Cholesterol absorption inhibitors that block the absorption of cholesterol in the intestines, such as ezetimibe
• Fibrates that regulate the amount of lipoprotein produced to carry cholesterol in the blood, such as fenofibrate

What is diabetes?

Diabetes is a condition where blood sugar levels (glucose) are too high and difficult to control.  Insulin, produced by the pancreas, is the main blood glucose regulating hormone.  It ensures that there is enough glucose needed for energy throughout the body, particularly the brain.  Glucose is produced in the liver and also absorbed from the diet.  Excess glucose is stored in the liver and muscles.  Hyperglycaemia is when too much glucose circulates in the blood, either because your body does not make enough insulin or has become resistant to the effects of insulin. 

Diabetes exists in two forms. Type 1 diabetes is usually hereditary, develops early in life, and is caused by damage to the pancreas due to attack by the body’s immune system.  Type 2 diabetes usually begins later in life and is related to lifestyle factors, including obesity, poor diet, smoking, and lack of exercise.

Diabetes increases the risk of serious health complications caused by damage to blood vessels.  Damage to large blood vessels like arteries (macrovascular) can cause cardiovascular disease resulting in heart attack and stroke.  Damage to small blood vessels like capillaries (microvascular) can cause kidney failure (diabetic nephropathy), and eye damage with loss of vision (diabetic retinopathy).  Damage to nerves (diabetic neuropathy) can result in amputation, particularly of the toes.

How do diabetic medications work?

Diabetic medications that are taken as tablets are known as oral antihyperglycaemics and are classed according to how they work.  They should be used alongside improving diet and increasing exercise and they include:

• Biguanides like metformin improve your body’s response to the effects of insulin, increase the amount of glucose that is stored, and reduce the amount of glucose produced in the liver and absorbed from the diet.
• Acarbose inhibits the action of the enzyme alpha-glucosidase that converts carbohydrates in the diet to simple sugars like glucose, and this reduces the amount of glucose that enters the blood after a meal.
• Thiazolidinediones like rosiglitazone and pioglitazone reduce insulin resistance by increasing the body’s response to insulin and acting directly on cells of the liver, muscle, and fat tissue.
• Sulphonylureas like glipizide increase insulin production by directly stimulating the pancreatic beta cells to produce more insulin.
• Gliflozins like empagliflozin and canagliflozin act directly on the kidneys to inhibit glucose reabsorption from the urine back into the blood, to lower blood glucose levels.
• DPP-4 inhibitors like sitagliptin work by inhibiting the enzyme dipeptidyl peptidase 4 (DPP-4) and preventing the destruction of incretins, which are small proteins released from the intestine after a meal that stimulate insulin production and reduce glucose production by the liver. 

Cardiovascular disease

Cardiovascular disease covers a range of heart and circulation problems that can increase the risk of heart attack and stroke.  These include:

• high blood pressure (hypertension) can damage your artery walls and increase stress on your heart, as well as increasing pressure on smaller blood vessels, such as those in the kidneys, which can lead to kidney damage. 
• heart failure, which is when the heart muscle is weakened and cannot pump blood efficiently.
• coronary heart disease when arteries of the heart become blocked and hardened.
• angina causing shortness of breath chest pain due to reduced oxygen supply to the heart muscle.
• Atherosclerosis, which is when cholesterol is deposited in the arteries causing them to become narrowed and hardened.

A heart attack is caused by restricted blood flow to the heart muscle, resulting in heart muscle cell damage.  A stroke is the result of a blockage in a blood vessel in the brain or a bleed into the brain, which can cause brain cells to die if not treated quickly. 

Risk factors for cardiovascular disease include having high blood cholesterol levels, lifestyle factors like obesity and smoking, and conditions like diabetes. 

Medications for cardiovascular conditions and how they work

We sell a wide range of generic Heart Meds, which are classed according to how they work.  Some of these medications are used only for a specific condition, but others can be used for several conditions.  For some conditions, more than one class of heart medication can be used together for increased effectiveness.

Our generic Heart Meds include:

• ACE inhibitors like enalapril and ramipril are used to treat hypertension and congestive heart failure.  They work by inhibiting the action of Angiotensin-Converting Enzyme, which relaxes and widens blood vessels, reduces blood volume, lowers blood pressure, and helps the heart to pump more efficiently relieving symptoms of heart failure. 
• Angiotensin II receptor blockers (ARB) like valsartan and losartan, are used to treat hypertension and congestive heart failure.  They work by blocking the hormone angiotensin II binding to its receptor, which relaxes and widens blood vessels, reduces blood volume, lowers blood pressure, and helps the heart to pump more efficiently, relieving symptoms of heart failure.
• Calcium channel blockers like diltiazem, amlodipine, and felodipine, are used to treat hypertension and angina.  They work by blocking calcium ions entering smooth muscle cells of blood vessel walls, allowing blood vessels to relax and widen.  
• Diuretics like the hydrochlorthiazide torsemide, are used to treat hypertension and congestive heart failure.  They work by acting on the kidneys to promote the removal of salts and water from the blood, which reduces blood volume, lowers high blood pressure, and helps remove fluid retention in the tissues (oedema).
• Anti-clotting drugs like clopidogrel are used to prevent blood clot formation (thrombosis).  They work by inhibiting platelet aggregation, which reduces the risk of a clot forming in the arteries that can cause heart attack or stroke if it travels to the heart or brain.
• Vasodilators like minoxidil are used to treat poor circulation, hypertension and angina.  They act directly on blood vessel walls, causing them to relax and widen, which allows blood to flow more freely.
• Beta blockers like propranolol and atenolol are used to treat hypertension, angina and arrhythmias (heart rhythm disorders).  They work by blocking the action of certain hormones like adrenaline that act on beta receptors in the heart, which slows the heart rate, widens blood vessels, lowers blood pressure, and increases blood flow and oxygen supply to the heart.  
• Antiarrhythmics like amiodarone are used to treat heart rhythm disorders, including irregular heartbeat (arrhythmia) and rapid heartbeat (tachycardia).  They work by correcting the abnormal electrical activity in the heart. 
• Heart rate lowering drugs called cardiotonic drugs like ivabradine are used to treat coronary artery disease, which is narrowing of blood vessels that supply the heart.  They work by acting directly on the heart muscle to reduce the heart rate.
• Anti-angina drugs like ranolazine are used to treat chronic stable angina, which is a symptom of heart disease.  They work by acting directly on the heart muscle to slow down the rate of muscle contraction, which reduces the need for oxygen and relieves symptoms of angina.

What is an infection?

An infection is when a microbe or microorganism invades the body and replicates, resulting in illness and disease with symptoms including pain, inflammation, fever and sores, depending on the type of microorganism and where the infection is located.  The infective organism is known as a pathogen and can enter the body by several routes, for example, through a wound, by inhalation, in body fluids, in contaminated food, or in a vector (another organism that transmits a pathogen).

An infection can be caused by:

• Bacteria, which are single cell organisms with a cell wall but no nucleus and all equipment needed to replicate their genetic material independently of the host cell.
• Viruses, which are much smaller than bacteria, are surrounded by a protein capsule and cannot replicate independently, instead they use the host cell enzymes to replicate their genetic material, which can be either DNA or RNA.
• Fungi, which are multi-cellular organisms that replicate independently and spread by growing hyphae, as in the case of mould-like fungi called dermatophytes such as tinea, or by budding as in the case of yeasts like candida. 

Parasities, which include protozoan or single-cell organisms that cause infections like malaria, dysentery, and giardiasis; also multicellular parasites like tapeworm.

Bacterial infections and antibiotics

Many bacteria live in the body without causing any harm, such as in the intestines where they help with digestion, or on the skin.  However, if bacteria invade the body, for example through a wound, by inhalation or in food, they can end up in a part of the body they are not meant to be and can become pathogenic by dividing and reproducing rapidly within the cells of the infected tissue.  This is a bacterial infection which can cause illness with symptoms including diarrhoea, fever, pain, inflammation and sores, depending on the type of bacteria and where the infection is located. 

Antibiotics are medications used to treat bacterial infections.  The mechanism of action varies between different classes of antibiotic and this determines how they work to prevent the spread of a bacterial infection.  Some antibiotics have a broad spectrum of action against many different bacteria, whereas some have a narrow spectrum and are used specifically for certain families of bacteria.  

Viral infections and antivirals

Viral infections are due to invasion of the host cell DNA by a virus, which then uses the cell’s enzyme to replicate so that new virus particles can be produced and shed ready to infect another cell, killing the host cell in the process.  

The symptoms of a viral infection depend on the location in the body that becomes infected.  The common cold is caused by infection of the upper respiratory tract and infection of the same tissues with influenza virus causes influenza.  Human Papillomavirus (HPV) infects skin cells, causing warts and is also associated with cervical cancer.  Herpes Simplex virus infects mucous membranes of the genitals (genital Herpes) and lips (cold sores).  Varicella, a Herpes-like virus, causes chicken pox and also shingles (herpes zoster). 

Viruses are not easy to treat, as unlike bacteria it is difficult to kill the virus without killing the body’s cells. However, there are antiviral drugs for treating viral infections, which work by several different mechanisms to prevent the growth and spread of the virus, but they do not kill the virus. An immunomodifier activates immune cells in outer layers of the skin to help fight invasion by a virus; other drugs kill infected skin cells.  Some drugs target viral enzymes, for example, an enzyme that is needed to replicate newly synthesised viral DNA.  

Fungal infections and antifungals

Fungal infections of the skin, scalp and nails are mostly caused by the tinea fungus which spreads through the skin and are commonly known as ringworm.  Yeasts also cause fungal infection, the most common being Candida, which infects mucous membranes of the mouth and vagina causing the infection candidiasis commonly referred to as thrush.  Symptoms of a fungal infection include rash, itching, scaling of the skin and inflammation.

Most anti-fungal treatments have a broad-spectrum of action and work in the same way.  They target a specific fungal enzyme needed produce ergosterol, which is a major component of the fungal cell membrane, and as a result the fungal membrane becomes weakened and leaks.  This kills the fungus and prevents spread of the infection.  

Parasitic infections and anti-parasitics

A parasitic infection is caused by a pathogenic microorganism and includes a range of organisms causing a range of diseases, some severe and life threatening.  A parasite can be a protozoan or single cell organism like plasmodium that causes malaria, amoeba that causes amoebiasis or amoebic dysentery, giardia that causes giardiasis, an infection of the intestines.  Parasitic helminth worms including tapeworm and roundworm cause intestinal infections that can cause severe symptoms.

Parasitic infections are often transmitted into the host by a vector.  For example, the mosquito that transfers the malaria-causing plasmodium when biting, directly into the blood.  Malaria is a life-threatening disease that causes symptoms including, fever, shivering, headache, vomiting, muscle pain, joint pain. Tapeworm infections are caused by ingestion of eggs in infected food or by transmission of the adult tapeworm in faeces, which become ingested due to poor hygiene.  The eggs are transmitted in the faeces of dogs or other mammals such as sheep, depending on the type of tapeworm.  Tapeworm causes a range of symptoms and diseases, depending on the location of the parasite in the body and the stage of its development, including abdominal pain, jaundice, coughing, chest pain, and seizures. 

Antiparasitics like metronidazole used to treat protozoal infections like amoebiasis (dysentery) and giardiasis target the single cell and prevent its replication.  The antimalarial, quinine, targets and kills the infective larval stage of the parasite.  Anthelmintics (dewormer) like albendazole targets all stages of the parasitie and disrupts its metabolism and its integrity, which kills the organism.