List the effects of drugs on body functions
Drugs and medicines alter:
- Physiological state: consciousness, activity level, and coordination.
- Incoming sensory sensations
- Mood and emotions
Groups that target:
- The nervous system
- Metabolic processes
- Immune system
The placebo effect - theraputic and healing effect from medicines that are parmacologically inert.
Outline the stages involved in drug development
- Identification of lead compound - a compound shown to have the desired biological activity
- Synthesis of analogues - making and testing many chemically related compounds
- Biological testing (on individual cells and tissues)
- Phase I: 50-100 healthy volunteers
- Phase II: 200-400 patients
- Phase III: 3000+ patients (half are given the drug under test, the other half a placebo; neither doctor nor patinet knowsh whcih preparation is being given).
- A review of the development research results before approval.
- Monitoring of the drug after it is released on the market.
Describe the methods of administering drugs
Oral - taken by mouth (tablets, capsules, pills, liquids).
Inhalation - vapour breathed in, smoking (medications for respiratory conditions such as astma; abusive drugs like nicotine and cocaine).
Skin patches - absorbed directly from the skin into the blood (Hormone trreatments, nicotine patches).
Suppositories - inserted into the rectum (treatment of digestive illnesses; hemorrhoids).
Eye & ear drops - liquids delivered directly to the opening (treatments of infections of the eye or ear).
Parental - by injection
- Intramuscular - many vaccines
- Intravenous (fastest method of injection) - insulin
- Subcutaneous - local anestetics, dental injections.
Discuss therapeutic window, tolerance, side-effect
Side-effects are physiological effects which are not indended and vary greatly form one drug to another, and with the same drug in different people. Side effects can be: beneficial (aspirin for pain relief protects against heart disease; benign (nausea, constipation); highly adverse (damage organs). The impacts of side-effects must be evaluated throughout the treatment in order to aviod dramatic consequences such as that of thalidomide.
Therapeutic window is the range of a drug's concentration in the blood between its therapeutic level and its toxic level. The dosing regieme depends on age, sex, weight, as well as diet and other potentially administered drugs, but regardless of these factors, the dosage should result in constant levels of the drug in the blood. However, this is not possible (unless administered via intravenous drip), which is why it is importnat that the concentraion in the bloodstream remains within a certain range: not to cause unaccaptable side-effects, but to have therapeutic outcomes.
Tolerance occurs when repeated doses of a drug result in smaller physiological effects. Higher doses are needed to produce the same effect, increasing the chances of there being side-effects. It is unclear how tolerance develops, but it is proposed that the body becomes able to metabolize and break down the drug, or that the drrug receptors become less effective. Tolerance is not to be confused with dependence or addiction, which occurs when a patient becomes dependent on the drug to feel normal and suffers from withdrawal symptoms if the drug is not taken.
Explain the reduction of excess stomach acidity
Drugs that help combat excess acid are known as antacids. They work by neutrolixing the hydrochloric acid, hence releiving the symptoms. Antacids are usually weakly basic compounds, often metal oxides ro hydroxides, carbonates, or hydrogencarbonates, which react with the acid to produce salt and water.
Examples: Al(OH)3 + 3HCl à AlCl3 + 3H2O; Mg(OH)2 + 2HCl à MgCl2 + 2H2O.
Some antacids contain both aluminium and magnesium compounds as they complement each other well; magnesium salts tend to be faster acting, but aluminium compounds tend to have a longer-lasting effect. Additionally, magnesium salts tends to act as laxatives, while alumnium salts cause constipation. Aluminium has been linked with the development of Alzheimer's.
Other antacids contain metal carbonates and hydrogencarbonates whcih react with the acid to produce salt, water, and carbon dioxide. This can cause bloating of the stomach, which can be reduced with antifoaming agents. Antacids can contain alginates which float to the top of the stomach preventing reflux into the oesophagus.
Examples: NaHCO3 + HCl à NaCl + H2O + CO2; CaCO3 + 2HCl à CaCl2 + H2O + CO2.