Drug distribution sjk

Presented by-
Ms.S.J.Kamble
Department of Pharmacology
Ashokrao Mane College of Pharmacy,
Peth Vadgaon

Definition
 Modification of drug response of one drug by another drug
when they are administered simultaneously
OR
 Alteration in the effects of one drug by prior or concurrent
administration of another drug.
 Due to ingestion of food: Drug-Food Interaction
 An interaction is said to occur when the effects
of one drug are changed by the presence of
other drug, herb, food, drink.
 An interaction occurs when pharmacokinetics or
pharmacodynamics of drug are changed.

 Drug-drug interactions occur when the
pharmacological activity of a drug is altered by the
concomitant use of another drug or by the presence of
some other substances.
 The drug whose activity is affected by such an
interaction is called the object drug and the agent
which precipitates such an interaction is referred to as
the precipitant.

• Types of drug interaction:
1. Drug-drug interaction
2. Food-drug interaction- Example: inhibition of
metabolism of several drugs(cardio-vascular drugs)
by grapefruit juice.
3. Chemical-drug interaction- Example: interaction of
drug with alcohol, tobacco etc.
4. Drug-laboratories test interactions- Alteration of
diagnostic laboratory test result in the presence of a
drug. Such as Levodopa and uric acid.
5. Drug-disease interactions- worsening of disease in
presence of a drug.

Consequences of drug-drug interaction:
A drug-drug interaction can delay, decrease, or
enhance absorption of either drug. This can decrease
or increase the action of either or both drugs or
cause adverse effects.

• Decreased effect – Tetracyclin taken with calcium
causes the Ca ions in the stomach to bind with the
antibiotic thus decreasing its absorption .
• Increased effect – pennicillin administered with
probenecid to reduce uric acid content thus
preventing gout.

Drugs likely involved in
interactions
Precipitating
drugs
 Drugs highly bound to
plasma proteins
• Used for long term
• Enzyme inducers or
inhibitors
• Two drugs simultaneously
given for same disease
• Narrow therapeutic
index
• Zero order kinetics
• Steep dose
response curves
Object Drugs

Effectsofdruginteraction
 Druginteractioncanresultin
 Increasedeffect–AdditiveorSynergistic effect
Increasedtherapeuticeffect good
Increasedtoxicor adverseeffect bad
 Decreasedeffect–Antagonisticeffect
Decreasedtherapeuticeffect
Decreasedtoxiceffect
bad
good
 Druginteractionsusuallyhappenunexpectedlyandresultin
adversedrugreactions
 Druginteractionsforgoodtherapeuticeffectsareusuallyused
intentionallyandtheirresultsarealreadyknownbyphysicians

 Synergistic drug-drug interaction : use of probenecid with
penicillins to block the renal tubular secretion of penicillin to
increase duration of action of penicillin.
 antagonistic drug-drug interaction : Ibuprofen enhances salt
retention by the body and the diuretic like furosemide gets the
body rid of the salt.

Outcomes of drug interactions
Desired (Beneficial
Effects)
undesired (Harmful
Effects)

• Some serious adverse drug reactions:
ADVERSE DRUG
REACTION
TYPE OF DRUG EXAMPLE
Anaemia (resulting from
decreased production or
increased destruction of
red blood cells)
Certain antibiotics Chloramphenicol
Liver damage Antibiotics
Iron supplements (in
excessive amounts)
Tetracyclin
-
Stomach or intestinal
ulcers
Anticoagulants Heparin
Warfarin
Kidney damage Antibiotics Gentamicin

FACTORS EFFECTING DRUG INTERACTION
1.Multiple drug therapy-
• Therapy in patients suffering from hypertension and
congestive heart failures includes anti-hypertensives
as well as digitalis that may lead to abnormal heart
rhythms.
• Concurrent use of non-prescription drugs, for eg;
aspirin along with herbal medications can lead to
drug interaction.
• Theoretically, there is 50% possibility for a drug
interaction to occur if patient is receiving 5
medications and 100% for 7 medications.

2.Multiple prescribers
One doctor may prescribe an anxiolytic to the patient
while other may prescribe antihistamine having
sedative properties that may cause excessive
depressant effect.
3.Multiple pharmacological effect of drug:
Most drugs exhibit more than one type of
pharmacological action and have the capacity to
influence many physiological systems. Hence, two
concomitantly used drugs may affect same system.
Eg: antihistamines enhance the sedative effect of
tranquillizers

4.Multiple diseases:Some patients take several drugs
owing to their suffering from more than one disease,
eg; patient with both diabetes and hypertension. In
this oral glyceamics and beta blockers can result in
decreased response to drugs resulting in elevated
blood sugar levels.
5. Poor patient compliance: This occurs when patient
does not take medications as intended by the doctor
that may lead to under-dosing thus a consequent
drug interaction.
6. Advancing age of patients: increased drug
interactions in elderly is mainly due to decreased
liver function.

Site of interaction:
 Outside the body.
 Inside the body.

Outside the body:
Incompatibilities: reaction of I.V drugs resulting in solutions
after mixing that are not longer safe for the patient alter
stability(change the PH) or structure leading to:
 Loss of drug activity.
 Formation of precipitates.
 Development of toxic product.

 Penicillin and aminoglycoside should never be placed in the
same infusion fluid because of formation of inactive complex.
 Protamine zinc insulin + soluble insulin lead to reduces the
immediate effect of the dose.
 With calcium – ceftriaxone precipitates in the lung and kidneys
premature neonates.
 Qunipristin and dalfopristin combination (antibiotics) used as
i.v. infusion is not compatible in N-saline so the infusion
solution should be prepare in 5% dextrose.

Drug Interactions Inside the body
 Pharmacokinetics drug interactions
 Pharmacodynamics drug interactions

Mechanism of drug interactions:
• Three main mechanisms by which interaction can
develop are:
1. Pharmaceutical interactions
2. Pharmaco-kinetic interactions
3. Pharmaco-dynamic interactions

Drug Drug Interactions
DI
Outside
the body
Syringe Iv fluids
Inside the
body
Pharmaco
kinetic
Pharmaco
dynamic

Pharmaceutical interactions
Also called as incompatibility, a physicochemical
interaction that occurs when drugs are mixed i.v
infusions causing inactivation or precipitation.
Example:Ampicillin interacts with dextran in solutions
further broken down to form chemical complexes.

Interactions outside the body
Mixing of the drugs in the same syringe
1. Thiopentone and succinylcholine
2. Carbenicillin inactivate
aminoglycosides
3. Hydrocortisone inactivates penicillins

Pharmacokinetic interaction
• These interactions are those in which the ADME
properties of an object drug is altered by the precipitant
hence known as ADME interactions.
• The resultant effect is altered plasma concentration of
the object drug.
•These can be classified as:
1.Absorption interaction
2.Distribution interaction
3.Metabolism interaction
4.Excretion or elimination interaction

Absorption interaction
• These are those where the absorption of the
object drug is altered.
• The net effect of such an interaction is;
a) Faster or slower drug absorption
b) More or less drug absorption

• Some important pharmacokinetic interaction
Object Drug Precipitant drug Influence on object drug
Absorption interactions
1. Complexation and Absorption
Tertracyclin like
cioprofloxacin
Antacids, food, mineral
supplements containing Al,
Mg, Fe, Zn, Bi and Ca ions.
Formation of poorly
soluble and unabsorbable
complex with such heavy
metal ions.
2. Alteration of GI pH
Sulphonamides, aspirin
Ferrous sulphate
Antacids
Sodium bicarbonate
Calcium carbonate
Enhance dissolution and
absorption rate
Decreased dissolution and
absorption rate.
3. Alteration Of Gut Motility
Aspirin, paracetamol,
levodopa
Levodopa, lithium
carbonate
Metoclopramide
Anticholinergics
Increased rate of
absorption.
Decreased.

Object drug Precipitant drug Influence on object drug
4. Alteration of GI Microflora
Digoxin Antibiotics Increased bioavailability
due to destruction of
bacterial flora.
5. Mal absorption syndrome
Vitamin A, B12, digoxin Neomycin and colchicines Inhibition of absorption
caused by neomycin

Distribution interaction
• Interaction where the distribution pattern of
the object drug is altered.
• Major mechanism is the alteration in protein-
drug binding.
Competitive displacement interaction
Displaced drug Displacer Influence
1. Anti-coagulants
(Warfarin)
2. Tolbutamide
Phenylbutazone,
salicylates
Sulphonamides
Increased clotting time,
hence increased risk of
haemorrhage.
Increased hypo-glycemic
effect.

Metabolism Interaction
Interaction where the metabolism of the object drug is
altered. By two ways:
1.Enzyme induction: increased rate of metabolism.
2.Enzyme inhibition: decreased rate of metabolism.
OBJECT DRUG PRECIPITANT DRUG INFLUENCE
1.ENZYME INDUCTION
1.Corticosteroid,oral
contraceptives,
phenytoin
2.Oral contraceptives,
hypoglyceamics,
coumarins.
Barbiturates
Rifampicin
Decreased plasma
level. Decreased
efficacy of object drug.
Decreased plasma
levels.

ENZYME INHIBITION
1. Tyramine rich food. MAO Inhibitors
Disulphiram,
metronidazole,trinidazol.
Enhanced absorption of
unmetabolised tyramine.
2. Alcohol Increased plasma
aldehyde level.

EXCRETION INTERACTIONS
• Interaction that result in change of the excretion
pattern of the drug.
• Major mechanism of action:
1) Alteration in renal blood flow
2) Alteration of urine pH
3) Competition for active secretion
4) Forced diuresis

EXCRETION INTERACTION
1.CHANGES IN ACTIVE TUBULAR SECRETION
a)Penicillin,
cephalosporin, nalidixic
acid.
b) Acetohexamide
Probinicid.
Phenylbutazone
Elevated plasma level of
acidic drugs; risk of toxic
reactions.
Increased hypoglycaemic
effect.
2.CHANGES IN URINE pH
Aphetamine, tetracycline,
quinidine
Antacids, thiazides,
acetazolamide
Increased passive
reabsorption of basic
drugs;
Increased risk of toxicity.
3.CHANGES IN RENAL BLOOD FLOW
Lithium bicarbonate NSAIDs Decreased renal clearance
of lithium; risk of toxicity.

Pharmacodynamic Interactions
A) Direct Pharmacodynamic
Interactions
1. Antagonism at same site
● Opiates with Naloxone
● Warfarin with Vitamin K

A) Direct Pharmacodynamic Inteactions
2. Synergism at same site
● Effects of depolarising skeletal muscle
relaxants potentiated by
antibiotics like aminoglycosides, polymixin B

A) Direct Pharmacodynamic
Interactions
3. Summation of similar effects at
different sites
● Effect of alcohol as a depressant
potentiated by other
centrally acting drugs
● Effect of trimethoprim and
sulfamethoxazole

A) Direct Pharmacodynamic Interactions
3. Summation of similar effects at different sites
B) Indirect Pharmacodynamic Interactions
1. Cardiovascular system
Loss of Antihypertensive action of ACEI with
NSAIDS Bradycardia- beta blockers + verapamil

2. Fluid and electrolyte imbalance
Thiazide and loop diuretics - hypokalemia

2. Fluid and electrolyte imbalance
3. CNS
Sedation- BZD+ Alcohol

Drug Food Interaction
• Orally administered drug- food- alter absorption
• 3 mechanisms
1. Dilutes drug
2. Complexation/ binds with drug
3. Changes gastric emptying time
4. Changes pH by GI content
5. Reduces surface area of stomach

• Eg-
 Tetracycline & Ciprofloxacin
Food- calcium or iron- complex- reduces absorption
 MAO inhibitor
MAO-liver- metabolism of noradrenaline, tyramine
MAO inhibitors- ↑ level
Food- Tyramine (Cheese, Alcohol, Banana, Chocolate)
Tyramine – systemic circulation- Heart failure, Severe Hypertension
 Bioavailability - enhanced by food
Ketoconazole, Griseofulvin
 Increase in pH of stomach- destruction of drugs
Penicillin G, Ampicillin, Erythromycin

• Eg-
 Absorption of drug- reduced- food
Aspirin, Isoniazide, Levodopa
 Food containing folic acid- Phenytoin & Oral contraceptives
 Food- Vit K- Egg yolk, Green leafy vegetables
Vit K- synthesis of clotting factors
Heparin & Warfarin- decreases anticoagulant affect

Drugs in Liver Diseases
1. Pharmacokinetic level
• Decrease the activity of drug metabolising enzymes
• Changes in the blood flow
1. Drugs undergoing extensive hepatic first pass
metabolism
2. Drugs which are inactivated in the liver
3. Drugs which are activated in the liver
4. Drugs which are partly metabolised
5. Due to reduced synthesis of albumin

Drugs in Liver Diseases
1. Pharmacokinetic level
2. Pharmacodynamic level
• CNS sensitivity of sedatives, opioids is increased
• Effect of anticoagulant is enhanced
• Altered fluid and electrolyte balance

Drugs in Renal Disease
• Drugs which are excreted unchanged
• Drugs which are partly metabolised, partly excreted
unchanged
• Drugs which are completely metabolised and then
excreted

Drug Interaction studies during drug developement
• Main objectives:
1. Any interaction large enough to require dose adjustment
2. Any interaction calls for therapeutic monitoring
3. Contraindication to concomitant use of any medication
• Interactions between
1. new drug and existing drug
2. metabolic enzymes (CYP1A2, CYP2B6, CYP3A4)
3. metabolites of the investigational drug
4. Transporter based interactions

Reducing The Risk Of Drug
Interactions
1.Identify patient’s risk factors.
2.Take patient’s thorough drug history.
3.Keeping knowledge of the drugs being used.
4.Avoid therapeutic regimens when possible.
5.Educate the patients.
6.Monitor therapy.
7.Individualize therapy.

Drug distribution sjk

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (20)

Similaire à Drug distribution sjk

Similaire à Drug distribution sjk (20)

Dernier

Dernier (20)

Drug distribution sjk