Pharmaceutic Phase : the rate at which a solid drug goes into solution after ingestion
The more rapid the rate of dissolution, the more quickly the drug is absorbed
composed of one or more substances
Drug + alcoholic extract
liquid with fine solid Drug particles
alcoholic solution of a volatile drug
mixture of two unblendable Drug substances
Drug dissolved in ethyl alcohol
Drug + blended with a large amount of dissolved sugars
the study of how the body handles a drug over a period of time, including...
Absorption: encompasses the drug’s progression from its pharmaceutical dosage form to a biologically available substance that can then pass through or across tissues. The transformation must occur before the active drug ingredient reaches the systemic circulation
Distribution: Distribution is the process whereby a drug is transported from the site of absorption to the site of action
Biotransformation: Metabolism of drug into metabolites. 1st stop is the Liver. Can either transform the drug into a more or less active metabolite, or make the drug more water soluble (for excretion).
Excretion/Elimination: Drugs are eventually eliminated from the body in either their original form or as metabolites. Excretion is the elimination of toxic or inactive metabolites from the bloodstream to organs of excretion
6 Factors affecting drug absorption?
Drug Dissolution: the rate at which a solid drug goes into solution after ingestion. The more rapid the rate of dissolution, the more quickly the drug is absorbed
Solubility of the drug: tendency of the drug to dissolve - must match the cellular constituents of the absorption site (water soluble for certain targets, lipid-soluble for others)
Concentration of the drug: high concentrations are absorbed much more rapidly than drugs administered in low concentrations
pH of the drug: Acidic drugs tend to be more rapidly absorbed when placed into an acidic environment (like
the stomach) Alkaline drugs are more rapidly absorbed in an alkaline environment (like kidneys)
Site of absorption & it’s blood supply: Drugs on the skin must pass through several layers of skin cells, whereas drugs on mucous membranes have fewer levels to pass through. IV drugs are near-instant. Drugs placed in areas of rich blood supply (sublingual) are absorbed much faster than lower supplied areas (subcutaneous). May be affected by many factors (temperature, shock...)
Absorbing surface area: lungs are huge SA, skin less.
measure of the amount of a drug that is still active after it reaches its target tissue after considering all of the absorption factors
4 Factors affecting drug distribution?
Cardiovascular function: the drug is initially distributed to organs that are highly perfused (brain, heart, kidneys and liver) Distribution to the GI tract, skin, muscles and fat is much slower. Medical or traumatic emergencies may influence distribution times
Regional blood flow: In certain types of shock (eg: cardiogenic) blood flow to the kidneys is often diminished which must be taken into account if administering a medication to target the kidneys as it will not reach the kidneys in adequate concentration to be effective
Drug storage reservoirs: drug may be stored in various sites (Plasma & Tissue reservoirs). These reservoirs store drugs by binding the drugs to proteins within specific tissues, which Delays the onset, and Prolongs the action of the drug
Physiological barriers: protective barriers that inhibit the movement of certain substances while permitting the passage of others (eg: blood-brain & placental barriers)
time required for the total amount of a drug in the body to diminish by
i.e. If a patient received a single dose of a drug with a half-life of 5 hours, the patient would have half of that dose left 5 hours later, one quarter of the original dose after 10 hours…
Usual drug elimination time?
Drug Elimination – Accumulation?
A drug that is not readministered is eliminated almost completely after 5 half-lives, but a regularly administered drug reaches a constant total body amount (steady state) after about 5 half-lives (go figure!)
Having reached a steady state, the drug’s concentration in the blood fluctuates above and below an average level
Drug Elimination – Clearance?
refers to the removal of a drug from the body. Slow clearance rate drugs are removed slowly, high clearance are removed rapidly
Drug Elimination - Onset, Peak and Duration?
Onset: of action refers to the time when the drug is sufficiently absorbed to reach an effective blood level and sufficiently distributed to its site of action to elicit a therapeutic response
Peak: As the body absorbs more of the drug, the concentration in the blood rises, more drug reaches the site of action and the therapeutic response increases - it peaks
Duration: As soon as the drug begins to circulate in the blood, it also begins to be eliminated, eventually the elimination exceeds absorption, and the drug’s effect begins to decline. When the drug concentration in the blood falls below the minimum needed to produce an effect, the drug action ceases even though there is still some left in the bloodstream. The duration of action is the length of time that drug concentration is sufficient in the blood to produce a therapeutic response
Factors that Influence the Actions of Drugs?
Age: Young - Liver and kidney function (metabolism & elimination) are not yet fully developed, so their response will be slower. Old - these organs deteriorate, producing similar effects
Body mass: The more mass a person has, the more fluid that is potentially available to dilute a drug. This is why most drug dosages are given in terms of body mass (mg / kg)
Gender: Most gender differences in drug response result from the relative body masses. The different distribution and amounts of body fat also affect the amounts of drug available at any given time
Environment: Various stimuli in the environment affect response to a given drug. Surrounding conditions, such as heat and cold also increases or decreases distribution and elimination
Time of administration: If taken immediately after eating, absorption rate will be different than if taken on an empty stomach
Pathological state: Several disease states alter the drug-response relationship (eg: kidney/liver failure)
Genetic factors: Genetic traits (such as lack of enzymes or a lowered basal metabolic rate) alter absorption or biotransformation
Psychological factors: mental state can also affect their response to a drug, eg: placebo effect
Pregnancy: Anatomical and physiological changes - Increased cardiac output / heart rate / blood volume, hepatic metabolism & BP. Possibility of a drug passing to the fetus - Some drugs cross the placental membrane, others do not. Drugs should only be administered in pregnancy when the potential benefits outweigh the risks
the mechanisms by which specific drug dosages act to produce biochemical or physiological changes in the body
Pharmacodynamic Phase – 4 different ways?
Bind to a receptor site: The force of attraction between a drug and it’s receptor site is called affinity, the greater the affinity the stronger the bond. Efficacy is the ability to cause the expected response. Different drugs may have different affinities and efficacies. Some drugs will compete for receptor sites with the stronger one (affinity) winning out
Change the physical properties of a cell: _
Chemically combine with other chemicals: _
Alter a normal metabolic pathway: _
Drug Agonists vs Antagonists?
Agonists: Bind to the receptor and cause it to initiate the expected response
Antagonists: Bind to the receptor site but do not cause the receptor to initiate the expected response
Alpha vs Beta Neurotransmitters?
Alpha-1: Peripheral vasoconstriction
Beta-1: Increased heart rate, force, and automaticity
Beta receptor memory hint: you have 1 heart and 2 lungs
Compendium of Pharmaceuticals & Specialties: lists all drugs and effects
4 Names of drugs?
Chemical name: A precise description of the drug’s chemical composition and molecular structure.
Generic name: nonproprietary name - abbreviated form of the chemical name of the drug
Trade name: Brand or proprietary name - copyrighted name designated by the drug company that sells the medication
Official name: - followed by the initials USP or NF. Denotes its listing in one of the official publications and is usually the same as the generic name
IM administration limits?
Ass Male: <5ml
Ass Female or child: <3ml
Arm Male: <2ml
Arm Female or child: <1ml
Drug admin & absorption rates?
One drug enhances he effects of another drug
2 drugs having a greater effect than each drug individually
Drug Therapeutic index?
A drugs lethal dose (for 50% of the population), divided by its effective dose (for 50% of the population).
Determines he safety of a drug: 10,000 is safer than 100
Pharmacologic family: classified by drugs chemical structure
Therapeutic family: classified by drugs Mechanism of Action & Therapeutic effect