DRUG INTERACTIONS

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DRUG INTERACTIONS IN LABOR A PRACTICAL VIEW
Dr.Mohamed El Sherbiny MD Obstetrics Gynecology
Senior Consultant Damietta General
Hospital Damietta Egypt
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Basic principles
DEFINITION Drug interaction means
modification of the effect of a drug by
concurrent administration of other drugs.
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ADVERSE BENEFICIAL INTERACTIONS
Adverse interaction includes 1-Loss of drug
action 2-Unexpected increase in drug
action 3-toxicity
Beneficial interactione.g.. Pethidine
Metochlopromide(Plasil) NaloxoneMorphia.
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Mechanisms Of Interactions
I-PHARMACOKINETICS Everything that happens to
the drug in the body
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II-PHARMACODYNAMIC Everything the drug does to
the body
N.B Interaction outside the body (Incompatibility
) e.g. ketamine is incompatible with barbiturate
diazepam
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I-PHARMACOKINETIC
What happens to drugs in the body?
Absorption Distribution Metabolism
Excretion
Absorption may be interfered with e.g. Al(OH)3
In most antacid adsorb digoxin Adrenaline to
local anesthesia prolong effect
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Distribution affected by Competition for
plasma protein binding E.gIndomethacine
displaces Warfarine . Free
Warfarine --gt anticoagulant effect
Excretion drug clearance affected by another
drug e.g
NaHC3 pH of renal tubules absorption of
Aspirin Phenobarbital (weakly acidic)
. their excretion their Effects.
8
Metabolism
Interfered with through liver enzymes

• Induction of liver micosomal Enzyme
• CYTOCHROME P450(7-10 days) e.g.
• Rifampicin, Phenobarbiton, Carbamaziben
  (Tegretol)
• Phenytoin
• They increase the metabolism and decrease
  activity of other drugs e.g.Theophyllin,
• Valproic acid

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Metabolism Cont..
Inhibitor of liver enzymes (a rapid effect)
e.g. Cemitidin,Erthromycin decrease the
metabolism and increase activity of other drugs
eg.Theophyllin,Anticoagulant
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2-PHARMACODYNAMIC
Synergism 1-Addition 224 e.g. B Blockers
Thiazide 2-Potentiation 225 Trimethoprinsulfme
thexasol
Antagonism(Opposing) B-Blockers
Propanolol(Inderal) prevent the bronchodilator
effect of Sulbitamol (Ventolin) or Terbutalin
(Bricanyl) Indomethacine inhibits biosynthesis
of Vasodilator natruretic prostaglandins
--gtinhibit diuretic effect of Lasix and Thiazide
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TOPICS
I -DRUGS USED IN ORDINARY LABOR C S.
II- -DRUGS USED IN LABOR WITH OBSTETRIC
DISORDERS.
III- DRUGS USED IN COMMON MEDICAL DISORDERS.
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I -DRUGS USED IN ORDINARY LABOR C S.
Analgesic Anesthetics
Antacids , H2 antagonist
antiemetisc
Antibiotics
Ecbolic (Oxytocics)
Intravenous additives
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Analgesic Anesthetics
Opioids BenzodiazepinsDiazepam(Valium) Midazolam
(Dormicum) Ketamine(ketalar or Kalypsol)
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Analgesic Anesthetics (cont.)

No2, Hydrocarbon inhalation anesthesia Fluthane
,Triline, Muscle relaxant. Conduction Anesthetics

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CNS depression producing drugs commonly used
during labor
e.g. Anesthetics, Opioid,Magnesium
sulfate ,Anticonvulsant, Metoclopromide Benszodiaz
epine,Promothiazine Skeletal muscle relaxant
,Barbiturate , Beta adrenergic blockers,
Antihistaminic, Antidepressants

Usually they potentiate each other
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Atropine
Used for preanesthetic medication
fetal Bradycaredia
Atropine has these effects Ketamin(Ketalar)
Delirium Metoclopramide Antagonize effect on
GI motility Opioid Constipation urinary
retention. Thiopental Vagal
effect Neostigmine Muscrinic action of
Acetyle cholin
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Opioid Morphine,pethidine,Butorphanol,
Nalbuphine ,fentanyl ,tramadol
Interactions
Other CNS depressants Maternal and fetal CNC
Respiratory depression hypotensione.
Anticholinergic Sever constipation Paralytic
ileus
18

• Naloxon(Narcan)
• Reverses the analgesic and respiratory effect of
  opioids
• Withdrawal symptoms in dependents
• Large dose may be required to reverse
  Butorphanol(Stadol)

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Pethidine
Mono amine oxidas (MAO) Inhibitors
Antidepressant(Parnate) Sever fatal reaction
(Excitation,sweating,sever hypertension) Metoclo
pramide Analgesia Emetic effect. But
Promethazine (Sparin) Analgesia. Oxytocine
Prostglandines Potentiaton.
Ranitidine Metoclopramide should given to
oppose the delayed gastric effect of pethidine
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Butorphanol(Stadol)
It is (k)agonist mixed (µ)agonist and
antagonist -2mg is comparable with 80mg
pethidine -2mg has respiratory depression of 10mg
morphine but greater doses has no further
depression(ceiling)
Effect is altered by Cimetidine,Erythromycine
Thiophylline( Hepatic)
Antagonizes narcotic effect of Pethidine
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Nalbuphine (NUBIN)
It is a (µ) partial antagonist and( k)
agonist 10mg 10mg Morphine or 50 mg
Pethidine Higher dysphoria fetal R.
depression (So not popular) Ceiling
effect with dose gt 30mg
InteractionConcurrent .or following (µ)
Analgesia Respiratory depression
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Tramadol (Tramal) (50mg) Weak µ agonist less
respiratory depression for the fetus 50mg Tramal
40mg Pethidine May antagonize
antiepileptics Carbamazepine (Tegretol)
decreases effect of tramadol
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Fentanyl
(Systemic ,Spinal Epidural) 100
times as potent as morphine. 50 ug 50mg
pethidine More maternal nausea and vomiting,
Similar neonatal side effect and More naloxon
need for antagonist compared to pethidine
Addition of Chloroprocaine(Nesacaine) .
. . . Fentanyl(Epidural) Unexplai
ned increase of post operative pain
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KETAMINE (KETALAR OR kLAPYSOL) 50mg/ml
- Obstetric analgesia0.3mg/kg anesthesia1mg/kg
or to supplement No 2 - It stimulate CVS ---gt
hypertension,tachycardia.increase C.output -
this effect is opposed by Bezodiazepine or
Volatile anesthesia
Interactions Thyroid hormoneHypertension
Tachycardia CNS depression producing drugs
HypotensionR.depression Halogonated inhalation
Delayed recovery
Thiopental or diazepam Dreams and illusion
of ketamine
Incompatible with barbiturate diazepam
May produce myocardial depression with
Labetalol(Trandate)
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Antianxiety ( minor tranquilizers)
Benzodiazepines
Midazolam (Dormicum)
Diazepam Valium
Should be limited to Status epilepticusAnexity W
as used for ECLAMPTIC fits
With CNS depression drugs Potentiate each others
- Antacids delay effect of oral Diazepam -
Cimitidine Erthromycin inhibit metabolism
Increase effect
Fentanyl or Thiopental Dose for induction
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Thiopental
Used to induce sleep If used as
anesthesia----gt Marked neonatal depression
CNS depression producing agents CNS
respiratory depression, Hypotension ,and prolong
anesthesia Hypotensive agents diuretics Additive
hypotension.
Rapid or high dose Ketemine(ketalar)
Risk of hypotension respiratory
depression MgSO4 CNS depressant
anaesthetic effects
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NO2
CNS depression Producing medication
Anesthetic requirement Hypotension
Respiratory depression
Methyledopa(Aldomet) Decrease anesthetic
requirement
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HALOTHANE (FLUOTHANE)
LABETALOLProfound hypotension
Ritodrin(Yutopar) Potentiate Arrhythmia
Hypotension
OXYTOCICS Decrease uterine respond
Catecholamines (Dopamin,adrenaline
,Noradrenaline ), Ephedrin or Cocaine
Risk of ventricular arrhythmia.
Nitrous Oxide Concurrent use Requirement
of the other Ketamine -----gtProlonged recovery
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Muscle relaxant
SUCCINYL-CHOLINE
MgSO4, Aminoglycosides ,or Ranitidine(zantac) Pot
entiate muscle relaxant effect
Digitalis toxicity (arrhythmia) due to shift of
intracellular K
Ketamine or Clindamycine Prolongs apnea
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Nondepolarizing Neuromuscular Blockers
Gallamine(Flaxidil),Atracurium(Tracrium),
Pancuronium(Pavulon)

• B adrenergic blockers Prolong the effect of
  Flaxidil Pavulon
• Calcium salt Reverses the blocking effect
• Opioids Additive central respiratory depression

• MgSO4 or Halothane Enhances blockade

N.B.. Atracurium(Tracrium) Has insignificant
placental transfer and rapid reverse.
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Conduction (Regional)Anesthetics
Increased effect byAdrenaline,Beta
blocker, Cemitidene, Diazipam,Ketamine and
opioids,
(
Local Infiltration Before and after episiotomy
or Emergency CS in absence of anesthetic
support 0.5 Lidocaine(Zylocaine) or
Chloroprocaine(Nesacaine)
Adrenaline will prolong the effect of Lidocaine.
or Chloroprocaine
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Conduction (Regional)Anesthetics Contin.
Paracervical block 1 Lidocaine. or
Chloroprocaine at 39 Oclock
Fetal bradycardia is commonNo longer recommended
Pudendal Block(before Forceps or Vacuum
delivery) 1 Lidocaine. or Chloroprocaine.
Patient under heparin may have troublesome
hematoma
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Spinal(Subarachonoid) block
Tetracaine(Pontocaine), Bupivacine(Marcaine)
(duration 90150m.
minutes) Lidocaine(6090 minutes). or
Chloroprocaine
The addition of 0.2 mg of Morphine
improves pain control during after delivery
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Epidural Analgesia For Vaginal delivery CS.
Compared with IV. Analgesia Epidural block
has Same degree of analgesia Longer labor
Chorioamnionitis, Forceps,and CS.
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Epidural Analgesia
Morphia ,Pethidin,or Fentanyl smaller dose of
Bupivacine (Marcaine) Rapid onset, Good pain
relief Shivering Tachyphlaxis of
prolonged administration But higher pruritis
(less with stadol) and U.retention
0.5mg Ketamine 0.25 Bupivacaine (Marcaine
) prolongs the duration of Caudal block with
reduction of the dose.
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Epidural analgesia ( Contin.)
Addition of Chloroprocaine(Nesacaine)
Fentanyl Unexplained increase of post
operative pain Addition of Lignocaine(
Xylocaine) to. Bupivacaine can precipitate
toxicity
-Uterine displacementHydration with balanced
salt solution--.gt Decrease incidence of
hypotension after Spinal or Epidural
block -Hydration with rapid infusion of 25 g
Glucose Can lead to fetal acidosis
,Hypoglycemia,Hyperbilirubinemia.
ParadoxicallyHypertension associated with
methergin is more common with spinal or epidural
block.
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ANTACIDS
Used in labor for prophylaxis with analgesia or
anesthesia before CS will neutralize gastric
contents in 90.
Gastric alkalinization The absorption
bioavailability of Some antimascarinics,Phenothi
azine ,Propranolol,Atenolol,Digoxine Indomethacine
.Prednisone , Phenytoin, Ranitidine(Zantac) With
Misoprostol (Cytotec ) -PE2- Diarrhea
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H2 receptor Antagonist Cimetidine(Tagamet)
Ranitidine (Zantac)
Inhibits Cytochrom450448 Increased level of
Phenobarbiton.,Diazepam, ,Phenytoin,Tricyclic
antidepressent Theophylline, ,Lidocaine) B
Blocker,C chanel Blockers Decrease level of
Metronidazol.
Ranitidine (Zantac) Weak enzyme inhibitor
Less interaction than Cimetidine
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ANTIEMETICS
Phenothiazines Promazine (Sparine)
Chloropromazine(Largactil )
Benzamide Metochlopramide(Primperan,Plasil)
Ondansetron (Zofran)
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Metochlopramide (Primperan,Plasil)
M
Used with opioid analgesia and preanaesthetic
medication to reduce gastric volume and
increase the tone of L.esophageal sphincter
With CNS depressant drugsPotentiate each others
Decreases absorption of Digoxine ---gt Decreases
its effect
Decreases effectiveness of Aldomet
Prolongation of action of Succinylcholine
Anticholinergics lessen GIT motility effects of
primperan
Opioids Primperan antagonize the emetic effect
Gastric volume Potentiats analgesic effect.
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Ondansetron (Zofran) Used in resistant
postoperative vomiting
Liver Enzymes Inhibitors(Cemitidin,Erthromycin
) Increase activity of Zofran
CYTOCHROME P450 Inducers (Rifampicin,Phenobarbiton
,Carbamazepine (Tegretol) Phenytoin,)
Decrease activity of (Zofran)
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Phenothiazines Promazine (Sparine)
Chloropromazine(Largactil)
They should be limited to Psychotic patients or
for sever nausea or vomiting
CNS depressants Potentiate each others
-Potentiate orthostatic hypotension with
Thiaside -Lower seizure threshold

Decrease effect of anticonvulsant increase
their toxicity- -Inhibit effect of
Adrenaline -Potantiate effects of
Anticholinergics
Potentiates respiratory depression of pethidine
and decreases analgesic effect
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ANTIBIOTICS
AMPICILLIN Potentiate Prednisolone,Digoxin,Thyo
phillin,Ergot
,
PIPERACILLIN(Piprel)Carbincellin(Pyopen)
Potentiate thrombolytic effect of
Heparin Aspirin
CEPHALOSPORINES Nephrotoxicity with
Gentamycin or tobramycin(Nebcin) Cephoperazon(Cefo
bid) Nephrotoxicity with aminoglycosides
and potentiate anticoagulant
effect of thrombolytics
PEN ICILLINS or CEPHALOSPORENS ) Mixing with
aminoglycosides Mutual inactivation
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ANTIBIOTICS (Cont.)
ERYTHROMYCIN (It is A hepatic enzyme
inhibitor)--gt
Potantiat effects of Digoxin,
vasospasm of Ergot Theophylline, Potantiat
effects of Some antiepeleptics As
(Phyntoin(Epanutin), Carbamazepine(Tegratol),Val
proic acid(Depakene)
METRONIDAZOL (FLAGYL) Potentiated by
Phenbarbitone and phenytoin Opposed by Cemitidine
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ANTIBIOTICS (Cont.)
AMINOGLCOSYDES 1-Mutual inactivation with
Penicillins or Cephalosporins 2-Indomethacine
--gt Nephrotoxicity in premature neonates 3-
Potentiate ototoxicity of Vancomycin (
combination for endocarditis and resistant staph)
dose monitor
4-Potentiate neuromuscular blocking agent
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OXYTOCIN
IV oxytocin with General Anesthesia. Sever
hypotensione With Hydrocarbon inhalation
anesthesia (Cyclopropan, Halothen,Enfluran
Isoflurin) Hypotension Maternal Sinus
Bradycardia Halothane,Enfluran Decrease oxytocic
effect
Caudal block with vasoconstritcors Potentiate the
effect of prophylactic Vasoprerssors ---gt
severe hypertension even rupture of cerbral
blood vessels
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OXYTOCIN
Pg E2 Pg E1 Additive effect
Non S. Anti inflammatory Opposing
Excessive Saline Water intoxication
Maternal Fetal convulsions Excessive 5
dextrose ?? Neonatal hyperbilirubenemia
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METHERGIN
With general anestheticPotentiate
vasoconstriction
Halothane gt1 Opposes oxytocic effect
--gtPostpartum hemorrhage
Sympathomimetics Hypertension Headaches
(additive)
Paradoxically Hypertension with Spinal
and Epidural anesthesia B blockers
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PROSTAGLANDINS
All Prostaglandins are potentiated with
concomitant oxytocin. Combination my be
used therapeutically
PgE2 PgE1 P f 2 ? with methergin of
Bp.
Prostaglandin E1(MisoprostolCytotic) The same
as in Pg E 2 PgE 1 Mag. Antacid --gt Diarrhea
?
ProstaglandinF2a May potentiate effect of
vasopressors MgSO4 the effect of Pf 2?
markedly
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INTRAVENOUS ADDITIVES
Guidelines Drugs should only be added when
constant plasma concentrations are needed .
In general one drug compatible should be added
Label Name, drug and date.
Drugs should not be added to
blood products, substitutes, manitol or sodium
bicarbonate
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Continuos or intermittent drug infusion?
Intermittent infusion It is used if the drug is
unstable or incompatible over infusion period
.
In 50 200cmm over 30 - 60 minutes
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Continuous in dextrose 5 or saline
Calcium gluconate - Digoxine Naloxone - Magansium
sulfate
Diazepam (Valium) or insulin in ( glass
container)
Oxytocin in Dextrose ?Hyperbilirubinemia
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Continuous in dextrose 5
Terbutaline (Bricanyl) - Ritordine (Yutopar)
Methyl dopa (Aldomet)
Pg E 2
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Intermittent in dextrose 5 or saline
Penicillins
Aztronate (Azactam)-Gentamycin -Tubramycin
Ceftrixone (Cefobid) Not with calcium -
Ceftazidime (Fortum)
Labetalol(Trandate) - Ranitidine(Zantac)
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Continuos or intermittent infusion
Atropine sulfate - Prostigmine - Adrenaline -
Noradrenaline
Cephradine (Velosef)
Cimetidine(Tagamet)
Metocolpramide(Primperan)
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II-LABOR OBSTETRIC DISORDERS
PRETERM LABOR PROM
PREECLAMPSIA ECLAMPSIA
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PRETERM LABOR PROM
TOCOLYTICS 1-Beta Adreneregic Agents 2-
Magnesium Sulfate 3-Calcium Channel Blockers 4-
Antiprostaglandines
Clucocorticoids Phenobarbital Vitamin
K1(Konakion) Antibiotics
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B adrenergics
Ritodrine(yutopar) - Terbutaline (Bricanyl)
Salbutamol(Ventolin) Ritodrine is the most
effective tocolytic (Selective B2 agonist )
Pulse BP Rennin Hyperglycemia
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Ritodrine (yutopar)
Interactions
--G.Anesth., Pethidine,or MgSO4Arrhythmia
hypotension -Atropine Increase B.P. -B
Blockers Decrease tocolytic effect.
-Asthmatic patients under B.AdrenergicsTachyphla
xis(drug resistance) -Diabetic patients Insulin
Antagonist( insulin requirement)
Corticosteroids or MgSO4 Pulmonary edema
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Calcium channel Blockers

• Nifedipine (Adalat, Epilat)
• Inhibits the influx of Ca ions into
  . myometrial cells
• Excellent for hypertensives .
• Can be used for
• Diabetics,
• M.valve prolapse
• Mild arrhythmia.

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Calcium channel Blockers Nifedipine (Adalat,
Epilat) Cont.
Neuromuscular blockade with MgSO4 (live
threatining) Severe hypotension with
Barbiuturat, B Blockers and with Fenanyl
Anesthesia
Low dose of both Nifidipen B adrenergics
(EpilateYutopar) better uterine relaxation
and fewer side effect
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Calcium Gluconate or Chloride
May antagonize the effect of calcium channel
blockers
Precipitate sever arrhythmia for patient taking
digitalis
Opposes the neuromuscular depression of
magnesium sulfate
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Nonsteroidal Anti inflammatory drugs(NSADs)
Indomethacin(Indocid) - Diclofenac(Voltaren,Olfen)
, Ibuprofen(Brufen) the safest during
pregnancy Naproxin(Naprosyn),Piroxicam(Felden)
The last 3 can be used during lactation .
Indication Antiinflammatory,Tocolysis.
Interactions Increase effect of
Digoxin,Aminoglycosidesantiepileptics
Decreased effect byProstaglandins,DiureticsB
blockers
The effect of Oxytoctics especially
Prostaglandins(PP.Hg)
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Magnesium Sulfate (used when there is
contraindication to Ritodrine
Action Anticonvulsant Peripheral effect
decreases
Acetyl Choline at myoneural junction or direct
effect at the muscle Central ? CNS depression
Tocolytic Altering calcium uptake(Little
effect if cervixgt2cm)
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Magnesium Sulfate
Has Antiarrhythmic and coronary
protector (Suitable for heart abnormalities ) But
with cautions of over load in valvular diseases.

Incompatibilities Calcium,
Bicarbonates Clindamycine, Hydrocortisone
Salicylates Infusion in Dextrose (Preeclampsia)
Saline (Tocolytics)
Corticosteroids or yutopar Pulmonary edema
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Magnesium Sulfate
Interactions Calcium gluconate
Antagonist CNS depressant drugs
Potentiation Digitalis
Heart block Nifedipine Potentiate
Hypotension neuro muscular block Beta
Adreneregics Pulmonary
edema Corticosteroid
Pulmonary edema PF2 ? (Enzaprost)Oppose its
effect in postpartum hemorrhage Neuromuscular
blockers Potentiation delay recovery.
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Magnesium Sulfate
Interactions Case reports.
2 Cardiac arrest at CS for preterm
labor FirstMgso4 Thiopental Supine
hypocavel 2 nd Mgso4 Methergin
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Patient under corticosteroid
Obstetric disorders Preterm Labor
Antiphospholipid and HELLP syndromes
Associated disorders Allergic ( eg. Asthma)
Hematologic disease ITP, Collagen disease (eg.
SLE), Shock states, Arthritis
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CORTICOSTEROIDS
Ephedrine--gt Increase metabolic clearance-gtless
effect Hepatic enzyme inducing agents(e.g..phenyto
in,Baribturates ,Carbamazepine,Rifampicin--gt
Increase clearance-gtless effect Digitalis ---gt
Arrhythmia (due to hypokalemia)
Nondepolarizing neuromuscular bloking agent--gt
Enhancing (due to hypokalemia) BUT
Pancuronium(Pavulon) is inhibited
(unknown) Insulin--gtMore insulin dose NSAIDS (
e.g. endomethacine) Potentiation of antirhumatic
effect GIT ulceration
Ritodrine (Yutopar)or MgSO4---gt Pulmonary edema
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Barbiturate
Induce microsomal enzymes leading to
Enhance metabolism ( effect) of
Corticosteroids,Digitalis ,Metronidazol
Digoxin,Phenothiazines,Tricyclic antidepressant
Hypotension with Calcium Channel Blockers
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PREECLAMPSIA ECLAMPSIA
Antihypertensive drugs Hydralzine
(Aprisoline) Labetalol (Beta Alpha
blockers)(Trandate) Calcium Channel
blockers(Adalat)
Anticonvulsive Mg SO4
72
Antihypertensive drugs used in chronic
hypertension
Diuretics Thiazids in intravascular volume
expansion
Drugs decreasing cardiac output B.blockors
Nonselective Propranolol(Inderal) B1
selective-No bronchospasm Atenolol(Tenormin) Praz
osin ? blocking(Minipress)-gtin Resistant cases
Centrally acting Methyldopa(Aldomet)
73
HYDRALZINE(Aprisoline)
Additive hypotensive effect with Aldomet
Drug of choice for acute control of sever
pregnancy induced hypertension May be used with
Methyldopa or B blocker for chronic
hypertension. NSAID(eg Indomethacine)Reduce
antihypertensive effect
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Labetalol(Trandate)
A combined Alpha Beta adrenergic blocker for
control of severe pregnancy induced
hypertension It may be used with thiazide for
chronic hypertension. Additive hypotensive
effect and Bradycardia with (Reserpine) Tremor
with Tricyclic antidepressant. Cimetidine
decreases the effect of trandate.
75
Methyldopa (Aldomet)
Drug of choice for essential hypertension Addit
ive hypotensive effect with
Hydralzine ,Beta adrenergic
blockersGeneral anesthetics. Reduced
hypotensive effect withTricyclic
Antidepressent,BarbiturateSympathomymetics NSAID
s(eg Indomethacine)Reduce its antihypertensive
effect.
Ephedrine is less effective when used with
aldomet MOA inhibitoers (Parnate)
Hyperexcitability and sever hypertension .
76
Propnanolol(Inderal)
. Effect by Cimetidine,LargactilHydralzin(Enz
ymeinheritors) , Effect byPhenytin,barbirurate
s Effect of TheophyllineXylocaine
Additive Toxicity Methergin Sever Hypertension
Requirement of Insulin NifedipenMyocardial
depression
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III- DRUGS USED IN COMMON MEDICAL DISORDERS.
Heparin Aspirin
Antidepressent Insulin
Adrenaline
Antihestaminics
Theophyllines
78
HEPARIN
Potentiated by Platelet aggregation inhibitors
as Dextran, NSIDs, Carbencillin Aspirin,Cephoper
ozonCefobid , Valproic acidDepakene
79
ASPIRIN
Low dose Aspirin is used for prophlaxis against
DVT , Antiphosplipid syndrome,prevention of Pre
eclampsia
Decreased effect by Corticosteroid(
metabolism). Requirement of Vit.K
Requirement of Heparin Platelet aggregation
inhibitors as Dextran,, Carbencillin,Cephoperozo
nCefobid , Valproic acidDepakene They
potentiate bleeding tendency Effec of NSIDs
80
Antidepressants
Tricyclics Impiramine(Tofranil) -
Amitriptyline(Tryptazol) Potentiate the action
ofCNS depressant D.Anticholinergics,
Antihistamines,oral anticoagulant,AntithyroidsPhe
nothiazine
Monoamine Oxidase inhibitors (MAO) Tranylcypromi
ne(Parnate) Hypertensive crises with Pethidine or
aldomet , metabolism of B Adrenergi
81
INSULIN
Hyperglycemic agents Corticosteroid,ACTH,Diureti
cs, Epinephrine,Thyroid hormone ( Decrease the
dose) Hypoglycemic agents NSAIDs,B.blockers
Labetalol (Increase the dose)
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Adrenaline
Increases toxicity of Antidepressent Beta
Blockers the pressor and bronchodilator
effect Hydralazine Reduced Pressor effect of
adrenaline Prolongs the effect of Local
anesthetic agents
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Antihistaminics
Chlorophenramine,Dimethenedine(Fenistil) Phenera
min (Avil) Celimestin(Tavegyl), Nonsedative
selective H1 antagonist Astemizol (Hismanal)
Loratidine (Claritine)
Potentiate anticholinergics CNS depressants
Ca channel blockers or Phenothiazine Increase
Risk of arrhythmia with Astemizol(Hismanal) but
not with Loratidine (Claritine)
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THEOPHYLLINE
Effect By 1-Liver enzymes inhibitors
as Cemitidine,Corticosteroid,Ertromycine,Proplanol
ol 2-AdditiveEphedrine ,KetamineHalothen.
Effect By- 1-Liver enzymes inducers
as Rifampicin,Barbiturates,Carbamazepin(Tegratol)
Phenytoin(Epanutin) 2-Antagonism
DiazepamMetoclopramide
85
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