Basic pharmco and kinetics

Introduction to Basic Pharmacology and Pharmacokinetics

University of Connecticut

School of Pharmacy

What do medications do?

In general, medications may do the following:

1. Alter the activity of cells

2. Replace substances that are deficient or missing in the body

3. Neutralize substances that are excessive or doing harm to body

4. Destroy cells that harm the body

What do medications do?

In general, medications do the following:

• Alter the activity of cells

• Replace substances that are deficient or missing in the body

• Neutralize substances that are excessive or doing harm to body

• Destroy cells that harm the body

Cells have specific functionsSome cells in heart are responsible for keeping the heart beating at a certain rate

Some cells in the liver break-down drugs and other chemicals

Some cells in the pancreas release insulin, a hormone to control blood sugar

Some cells in our stomach release acid to digest food

Some cells in our guts absorb food, nutrients and drugs into the body

Some cells in muscle controlling how the muscle contracts and relaxes

Lock and Key- Receptor Signaling

Agonist vs Antagonist

Go and Do It!

Stop! Don’t do it!

Blocker

Medicines may alter cell functions

• Digoxin affects the cells in heart that regulate the rate of heartbeat

• Glibenclamide affects the cells in the pancreas to increase insulin release

• Hydrochlorothiazide affects the cells in kidney to increase loss of water in urine

Pharmacology – How do drugs work?

• Altering the activity of cells

• Replacing substances that are deficient or missing in the body or are needed in higher amount

• Neutralizing substances that are excessive or doing harm to body

• Destroying cells that harm the body






Deficiency could be Disease

• Patients with Type 1 Diabetes don’t have cells that release insulin

• Some diabetes patients may need to inject insulin to treat diabetes

Drugs may replace the Deficiency

Deficiency could be Disease

Low calcium in diet increases risk of osteoporosis, a condition of weak bones that break/fracture easily.

Calcium supplement can keep bones strong to prevent fractures

Drugs may replace the Deficiency











Drugs may neutralize

After we eat, cells in our stomach release acid to digest the food. This acid does not bother us as long as it’s within the stomach.

Sometimes when excess acid is released, it moves from its natural place in the stomach up into the food pipe. This causes a burning sensation around the chest.

Antacids, like calcium carbonate, work by reacting with and neutralizing the excess acid.










• Destroying cells or organisms that harm the body

Drugs may kill harmful cells or organisms

• Mebendazole kills harmful worms or parasites that infect our guts (intestines)

• Amoxycillin is a drug used to kill bacterial cells during certain bacterial infections

• In cancer patients, chemotherapy drugs are used to kill tumor cells





• Destroying cells or organisms that harm the body

Pharmacokinetics The trick to right dose

Too High or Supra-therapeutic dose

Too Low or Sub-therapeutic dose

Optimal dose

Drug Concentration in Blood

Time

Pharmacokinetics – How much drug is there?

• Absorption

• Distribution

• Metabolism

• Excretion

Absorption

• Some medicines work from outside the body – Dettol or Povidone Iodine to clean a wound

• Most medicines need to enter the body– Drug needs to overcome body’s barrier to

entry eg. gut wall for an oral drug

Routes of Administration

Most Common: • Oral (Tablet, Capsule, Liquid)• Injectable (IV/IM/SQ Injection)

Less common:• Rectal (Suppository, Cream)• Inhaled (Inhaler)• Dermal (Cream, Ointment, Lotion)• Vaginal (Suppository, Cream)• Intra-nasal (Spray)• Ophthalmic/Ocular (Eye or Ear drops)

Oral Absorption

Absorption through Stomach

ACIDIC

Absorption through Small Intestines

Food can affect absorption

Absorption throughLatter Parts of Small Intestines &

Large Intestines

Factors affecting Oral Absorption

• Breaking-down and dissolution of drug particles

• Digestive system’s movement and mixing of drug

• Presence and type of food

• Ability to pass through gut wall

• Stability of drug to enzymes

• Blood flow to the gut


• Absorption

• Distribution

• Metabolism

• Excretion

Distribution

• Describes how the drug circulates in the blood to different parts of the body after absorption

• Affects concentration of drug at the target organ

Drug in Gut Drug in Blood Drug in Target Organ

ABSORPTION DISTRIBUTION

Drug

Factors Affecting Distribution

• Flow of blood to the different organs

• Drug’s tendency to bind to proteins in blood

• Drug’s ability to cross the wall of blood vessel and/or other barriers and enter the target organ


• Absorption

• Distribution

• Metabolism

• Excretion

Metabolism• Better described as conversion or transformation of drugs

– Generally converted to a more water-soluble form so it can be easily excreted in urine

• Enzymes specialized to detoxify natural toxic compounds can also affect drugs

• These enzymes are located primarily in LIVER but may also be found in other places like kidney, lungs or gut wall

• Drugs may be converted to:– Less toxic or effective compounds– More toxic or effective compounds– Compounds with different type of effect or toxicity

Factors affecting Metabolism• Race

– Different ethnicities have different metabolizing capabilities• Age

– Reduced in elderly and children• Sex

– Women are slower in metabolizing ethanol than men• Disease state

– Patient’s condition of liver may affect metabolism• Other drugs

– Some drugs, eg cimetidine, slow down the conversion process of some other drugs

– Some drugs, eg carbamazepine, speed up the conversion process of other drugs

• Food– May speed up or slow down metabolism


• Absorption

• Distribution

• Metabolism

• Excretion

Excretion

• Process of eliminating or throwing out the drug (either actual or converted) from the body

• Primarily happens through KIDNEY with urine but also through other organs– Feces (if poorly absorbed in gut or if diarrhea)– Lungs– Skin– Breastmilk in lactating women

• Use caution with dose if patient’s kidney function is poor

• Use caution if patient is breastfeeding

Drug Interactions• A drug’s effects is not solely determined by itself. Drugs interact with

other things.

• Drug interactions can increase or decrease the desired or undesired effects of drug

• Three broad categories of drug interaction:– Drug-Drug

• One drug’s effect changed by another drug • Eg. Increased/decreased metabolism in liver• May happen when two or more drugs are taken

– Drug-Food• Drug’s effect changed by food • Eg. Decreased absorption by binding in the gut.

– Drug-Condition• Drug’s effect changed by patient’s health condition• Eg. Harmful effects to a fetus when patient is pregnant

Effects of Drug Interaction

• Four general types of interaction effects:– Additive (3+2=5)

• Enalapril + Hydrochlorothiazide can lower blood pressure more than either drug alone

– Synergistic (3+2= 50)• Paracetamol + Alcohol can increase risk of liver toxicity

– Potentiation (0+2=20)• Metronidazole + Alcohol can cause serious side effects or

sudden death• Enalapril + Pregnancy can cause injury or death of fetus

– Antagonism (3+(-2)=1)• Doxycycline + Calcium/Milk taken together can decrease the

absorption and therefore effectiveness of Doxycycline• Poison + Antidotes may cure the toxic effects of poison

Date post:	07-Jul-2015
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Basic pharmco and kinetics

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