This is to explain why do drugs come in different forms. A medicine or any chemical substance which has a physiological or psychological effect in an organisms when ingested or introduced into the body. Medicines are basically given based on their target organ and mode of action desired, so if one wants a medicine for stomach, it makes sense to give a tablet which can then directly go to stomach and act. This works if you have direct access to the organ desired, like stomach, Intestines (especially large intestine through anal suppositories), mouth (through orally solvable tablets), skin (through ointments, lotions etc.). Problem occurs when you need drugs which act on organs you cannot directly have access to, like heart, Brain, small intestine, Pancreas, blood etc. For these we use different route of administration and special formulations like Capsules (which do not get disintegrated by gastric acids and can directly go to small intestine where they can dissolve and initiate their actions), Buccal or dermal patch (where you do not want immediate action but long lasting action) etc. Drugs consumptions can be through Injection, Smoking, Inhalation, Absorption via a patch on the skin, Ingestion, suppository and/or Dissolution under the tongue. According to route of action:
1. If we need immediate action we use sublingual tablets, which provide almost immediate action in emergency cases like heart attacks, where nitroglycerine is given for immediate relief.
2. Oral route is the most preferred route when there is no emergency, its one of the most comfortable and has the lowest cost but has other disadvantages like irritation of gastric mucosa, delay in onset of arrival and other unwanted metabolic reactions like drug being acted upon by intestinal enzymes. Different forms are Tablets ( It comprises a mixture of active substances and excipients, usually in powder form, pressed or compacted from a powder into a solid dose), Capsules (where the drug is enclosed in a gel like covering allowing it to pass the barriers like stomach acids and be used as anal suppositories, also liquid form of drugs can also be given as capsules), syrup ( not much difference but some drugs are more active in liquid form, and sometimes its more comfortable like in case of children)
3. Topical (mostly cream or ointment): By delivering drugs almost directly to the site of action, the risk of systemic side effects is reduced. However, skin irritation may result, and for some forms such as creams or lotions, the dosage is difficult to control as it depends on the person applying the lotion/cream.
4. Inhalation (breathed into the lungs): Inhaled medications can be absorbed quickly, and act both locally and systemically. Proper technique with inhaler devices is necessary to achieve the correct dose. Some medications can have an unpleasant taste or irritate the mouth. Inhalation by smoking or inhaling a substance through inhalers is likely the most rapid way to deliver drugs to the brain, as the substance travels directly to the brain without being diluted in the systemic circulation and effects are more potent. eg Cigarette smoking
5. Injection: The term injection encompasses intravenous (IV), intramuscular (IM), and subcutaneous (SC) administration. Injections act rapidly, with onset of action in 15-30 seconds for IV, 10-20 minutes for IM, and 15-30 minutes for SC. They also have essentially 100% bioavailability meaning all drug injected goes directly into system, this can be used for drugs that are poorly absorbed or ineffective when given orally. Some medications, such as certain antipsychotics, can be administered as long-acting intramuscular injections. Ongoing IV infusions can be used to deliver continuous medications or fluids. Disadvantages of injections include potential pain or discomfort for the patient, and the requirement of trained staff using aseptic techniques for administration.

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