Basic Pharmcology and Pharmacokinetics
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Transcript of Basic Pharmcology and Pharmacokinetics
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
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
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
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
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.
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
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 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
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 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
Pharmacokinetics – How much drug is there?
• 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
Pharmacokinetics – How much drug is there?
• 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
Pharmacokinetics – How much drug is there?
• 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