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Essential Drugs Concept and Routes of Drug Administration

Although there are many drugs on the market, the majority of them may not be essential for the majority of people.

Essential Drugs Concept

Although there are many drugs on the market, the majority of them may not be essential for the majority of people. Based on this fact, the World Health Organization (WHO) created the concept of "essential medications" in 1977. Essential drugs, according to this definition, are those that meet the population's most pressing healthcare demands. They are chosen with public health significance, proof of safety and efficacy, and comparative cost-effectiveness in mind. Essential pharmaceuticals are intended to be available at all times, inappropriate dose forms, with guaranteed quality and enough information, and at a cost that individuals and communities can afford within the framework of functional health systems. The idea of necessary medications is designed to be flexible and adaptable to a wide range of scenarios; whether drugs are deemed essential remain the responsibility of the government in question.

In the initial iteration of the list of essential medications, published in 1977, 208 drugs were designated to meet the global illness load at the time. A group of impartial specialists revises the list every two years to reflect new health issues, medicinal breakthroughs and shifting microorganism resistance trends. WHO celebrated its 30th anniversary in 2007. By that time, 156 of the 193 WHO member countries had formal essential drug lists, with 127 upgrading them in the previous 5-10 years. The 2007 list of critical medicines includes 340 medications for malaria, HIV/AIDS, TB, reproductive health, chronic disorders such as cancer, and diabetes. For the first time, "Necessary Medicines for Children" was included in the list of essential medicines issued in October 2007. Every two years, the list of necessary medications for children is also revised. In 2015, the World Health Organization (WHO) published the 19th model list of essential medications and the 5th revised list of essential medicines for children. The 20th review of necessary medications is underway, as is the sixth revision of essential medicines for children.

Routes of drug administration

  • The elements are as follows:
  • The drug's characteristics.
  • Use in an emergency or on a regular basis.
  • The drug's site of action—local or systemic.
  • The patient's age
  • The influence of stomach pH, digestive enzymes, and first-pass metabolism
  • Choice of the patient/doctor (sometimes).

Local routes

It is the most basic method of delivering medicine to the location where the desired effect is required. There are only modest systemic negative effects.


The drug is administered to the skin or mucous membrane in various areas for local action.
  • Oral cavity: as a suspension.
  • GI tract: As a non-absorbed pill, such as neomycin (for gut sterilization prior to surgery).
  • Rectum, vaginal, and anal canal
As an enema (rectal injection of a liquid drug):
- For example, a soap water enema, in which the soap acts as a lubricant while the water stimulates the rectum, is an enema for bowel evacuation.
- Methylprednisolone retention enema, for example, in ulcerative colitis.
As a suppository (delivery of the medicine in a solid form into the rectum), e.g., bisacodyl—for bowel evacuation.

  • There is little first-pass impact.
  • Can be used to treat vomiting.
  • It is possible to deliver it to a patient who is unconscious.
  • Higher therapeutic concentrations of medication are readily obtained in the rectum.
  • For fast intestinal evacuation, often during gut sterilization prior to any surgical or radiological treatment.
  • Inconvenient.
  • The absorption of drugs is delayed and irregular.
  • Rectal mucosal irritation or inflammation can occur.
- Eye, ear, and nose: Eye/ear drops, ointments, and sprays containing Gentamicin (for infection, allergic diseases, and so on).

Salbutamol inhalation for the bronchi (for bronchial asthma and chronic obstructive pulmonary disease). Gases, volatile liquids, and solids (in the form of finely divided particles) are inhaled for systemic and local effects. Insufflation is the term used to describe the inhalation of solids.

  • Because of the wide surface area, the medication is absorbed quickly.
  • The initial pass's impact is averted.
  • Localized effects that occur quickly
  • Only a few medications can be provided.
  • Irritation of the pulmonary mucosa may occur.
  • The procedure is inconvenient.
  • Cardiotoxic effects are possible.
  • Clotrimazole (antifungal) ointment, cream, lotion, or powder for cutaneous candidiasis.
- Transdermal: Transdermal patches can distribute drugs in a regulated or extended manner (iontophoresis). Low dosage, low MWt, fat-soluble medicines provide improved systemic absorption (transdermal).

- Intra-arterial path: This is a seldom-used route. It is mostly employed in diagnostic examinations such as coronary angiography and for the delivery of certain anticancer medications, such as for the treatment of limb cancer.

- Injection of medication into deep tissues, such as triamcinolone injections directly into the joint space in rheumatoid arthritis.

Systemic route (external)

Oral route

It is the most popular and well-accepted method of medication delivery. Oral dosage forms include tablets, capsules, syrup, and mixtures, for example, paracetamol tablets for fever and omeprazole capsules for gastric ulcers.

  • Convenient - portable, safe, painless, and self-administrable.
  • It is inexpensive since there is no need to sterilize it (but must be hygienic of course)
  • There are several dose forms available, including quick release tablets, capsules, enteric-coated tablets, multilayer tablets, delayed-release, solutions, and mixes.
  • Convenient for frequent and extended usage
Oral medicines are delivered to the systemic circulation via the liver in the first-pass effect. During absorption, highly metabolised drugs will be digested in the liver. For example, the oral dose of propranolol is somewhat greater than the IV dose, and the same is true for morphine. Both of these drugs, as well as many others, go through considerable processing in the liver.

First Pass Effect
Drug absorption might be affected by both food and G-I motility. Frequently, patient instructions contain a recommendation to consume with meals or on an empty stomach. Tetracyclines and penicillins, for example, absorb more slowly with meals. However, bioavailability of propranolol is increased after eating, while absorption of griseofulvin is higher after a fatty meal.

Local effect: Antibiotics may destroy normal gut flora, allowing fungal forms to proliferate. As a result, an antifungal agent may be used with an antibiotic.

If the patient is unconscious, he or she must be able to consume solid dosage forms. Liquids can be administered through the tube.

Buccal and sub-lingual route

  • Some medications are administered in the form of tiny pills that are held in the mouth or under the tongue.
  • These are dose forms that are either buccal or sublingual.
  • Buccal tablets are typically tougher tablets [4-hour disintegration time] that are meant to breakdown slowly. Nitroglycerin, in the form of a softer sublingual tablet [2-minute breakdown time], may be utilized to provide immediate relief from angina.
  • Some steroids, including testosterone and oxytocin, are also administered in this manner. Nicotine-containing chewing gum can be used to replace cigarette smoking.
  • The action begins quickly.
  • The action can be stopped by spitting out the tablet.
  • It avoids first-pass metabolism.
  • It is feasible to self-administrate.
  • It is not appropriate for bitter-tasting or unpleasant drugs.
  • It is not appropriate for irritants or lipid-insoluble medicines.
  • It is not possible to administer to a patient who is unconscious.
  • Large quantities cannot be distributed.
  • Cannot be taken in cases of severe vomiting.

Rectal route

Drugs can be administered as a solid or as a liquid.

Suppository: It can have both local (topical) and systemic effects, such as indomethacin, which is used to treat rheumatoid arthritis.

Enema: Retention enema has both local and systemic effects. The medicine is absorbed through the rectal mucous membrane and has a systemic impact, such as diazepam for paediatric status epilepticus.

  • There is little first pass impact.
  • Can be used to treat vomiting.
  • It is possible to deliver it to a patient who is unconscious.
  • Higher therapeutic concentrations of medication are readily obtained in the rectum.
  • For fast intestinal evacuation, often during gut sterilization prior to any surgical or radiological treatment.
  • Inconvenient and unpopular. There may be some pain.
  • Drug absorption is sluggish and inconsistent.
  • The rectal mucosa may become irritated or inflamed.

Parenteral route

Because the onset of action of medications is faster, it is appropriate for use in an emergency.

Useful for: 
  • Unconscious patients.
  • Patients who are uncooperative and untrustworthy.
  • Patients who have diarrhoea and are vomiting.

It is appropriate for:
  • Drugs that cause irritability.
  • Drugs that are not absorbed orally.
  • Drugs are degraded by gastric secretions.
  • Aseptic conditions are required.
  • Typically, it cannot be self-administered.
  • Local tissue harm to nerves, arteries, and other structures is possible.

Intravenous (IV)

Drugs can be injected directly into the circulation through a vein or infused into a peripheral vein for 1 to 2 minutes or longer.
Drugs are given as follows:
  • Bolus: A single, rather large dosage of a medicine injected fast or slowly into a vein as a single unit. In the case of a bleeding peptic ulcer, for example, intravenous ranitidine.
  • In myocardial infarction, for example, slow intravenous administration of morphine.
  • Intravenous infusions include dopamine infusions for cardiogenic shock, mannitol infusions for cerebral oedema, and intravenous fluid infusions for dehydration.
  • The bioavailability is 100%.
  • Because of its rapid beginning of action, it is the preferred method in an emergency, such as intravenous diazepam to control convulsions in status epilepticus.
  • Large amounts of liquids, such as intravenous fluids, can be given to those who are severely dehydrated.
  • Because highly irritating medications, such as anticancer treatments, are diluted in blood, they can be administered.
  • In cerebral oedema, a hypertonic solution, such as 20% mannitol, can be administered intravenously.
  • A steady plasma level of the medication can be maintained through i.v. infusion, for example, dopamine infusion in cardiogenic shock.
  • The drug's effect cannot be stopped after it has been administered.
  • Phlebitis can be caused by local irritation.
  • Self-medication is not an option.
  • Aseptic conditions must be met.
  • Some medications can induce tissue damage, necrosis, and sloughing by extravasation.
  • The I.V. route cannot provide depot preparations.
  • In most cases, the drug should be administered gently.
  • Before injecting, ensure sure the needle's tip is in the vein.

Subcutaneous (S.C.) route

Adrenaline, insulin, and other medications are injected into the thigh, abdomen, and arm subcutaneous tissues.Advantages
  • The medications' effects are consistent and long-lasting.
  • Drugs can be given even if vomiting and diarrhoea are present.
  • Unconscious patients can be given drugs.
  • The impact of the first pass is avoided.
  • It is possible to deliver drugs that are not absorbed by G.I.T.
  • It is possible to regulate oneself (e.g., insulin).
  • Depot formulations, such as Norplant, can be put into the subcutaneous tissue for contraception.
  • Only non-irritant medications can be used; otherwise, significant irritation, discomfort, and necrosis of subcutaneous tissues might ensue.
  • Drug absorption is slower than with I/M injection.
  • Expensive.
  • If proper sterilization steps are not taken, there is a danger of infection.
  • Large doses of medication cannot be administered.

Intramuscular route

  • The medication is injected deep into a huge skeletal muscle's belly. The detoid, triceps, and gluteus maximus are often used muscles. The maximus, rectus, and femurs are all present, depending on the animal's species.
  • Because the muscle has fewer sensory nerves, injecting a drug 1m away is less painful.
  • Drug absorption from the gluteal region is slowed due to increased fat deposition, particularly in females.
  • Deep intramuscular injections are administered in the upper outer quadrant of the buttock to protect important nerves.
  • Deep I/M injections are less painful than I/M injections in the arm because of the high fat content.
  • Intramuscular injections are delivered at a 90-degree angle.
  • The rate of absorption is constant.
  • Action begins quickly.
  • Irritant substances can be administered.
  • Unconscious patients can be given drugs.
  • Dosage accuracy is assured.
  • Useful in times of need.
  • The impact of the first pass is avoided.
  • Drugs that cause gastric irritation can be administered.
  • It is possible to deliver drugs that are not absorbed by G.I.T.
  • A modest amount of medicine, up to 10 ml at a time, can be administered.
  • Localized pain and the formation of an abscess
  • Self-administration is challenging and needs the support of a technical professional.
  • Expensive.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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