Give reason Flashcards
1- Give an account on the relation between B-blocker and sulfonylureas.
a. Augment their hypoglycemia & ↓ compensatory hepatic glycogenolysis.
b. Mask sympathetic manifestation of hypoglycemia —> Silent coma.
2- Give reason sulfonylureas cannot be used in type I diabetes.
their action depends on presence of preformed endogenous insulin which is not present in patients with DM type 1.
3- Give reason Metformin cannot be used in renal impairment.
Cannot excrete lactic acid.
4- Give reason thyroid hormone replacement therapy increase during pregnancy.
A higher dose of L-T4 is often required in hypothyroid pregnant. as early development of the fetal brain depends on maternal thyroxine.
5- Give reason, thioamides take long
time for a clinical response to appear.
a. The long t1/2 of thyroxine.
b. The large store of the hormones in the gland.
6- Give reason B-blocker is given in cases of hyperthyroidism.
Used to control peripheral manifestations of hyperactivity of the sympathetic nervous system occurring secondary to hyperthyroidism.
7- Give reason octreotide is better than somatostatin.
Its half-life is longer than that of the natural compound, and depot formulations are available, allowing for administration once every 4 weeks.
8- Give reason desmopressin is better than vasopressin in treatment of diabetes insipidus and nocturnal enuresis.
Has minimal activity at the V1 receptor → largely free of vasopressor effects and Is longer acting than vasopressin.
1- Explain the risk associated with removal of bacteriostatic drug before the immune system eradicate the organism.
Enough viable organisms may remain to begin a second cycle of infection.
2- Give reason it is advisable to treat patients with monotherapy.
- reduce the possibility of superinfection.
- the emergence of resistant organisms
- minimizes toxicity.
3- Give reason Benzyl Penicillin (Penicillin G) not given orally.
Acid sensitive = Destroyed by gastric acidity.
4- Give reason Benzyl Penicillin (Penicillin G) not effective in treating
Staphylococcus aureus.
Lactamase (Penicillinase) sensitive = NOT effective in β-lactamase secreting organisms as staph. Aureus.
5- Give an account on combination between penicillin and aminoglycoside.
Anti-pseudomonal penicillin can be combined with aminoglycoside for pseudomonal infection outside the urinary tract, Synergism and decrease resistance can Occur.
6- Explain why β-Lactamase (Penicillinase) Inhibitors are added to penicillin
They bind with the enzyme → Irreversible inhibition → Suicide substrate.
They protect penicillins from inactivation by β-lactamases secreted by some bacteria
8- Give reason Meropenem (Meronam) is better than Imipenem because:
a- Not metabolized by dihydropeptidase enzyme.
b- Less liable to produce seizures.
9- Give reason Vancomycin is not given rapid IV infusion.
Rapid IV infusion → Histamine release → Red man syndrome & Shock.
10- Explain the relation between tetracyclines and calcium.
When they are taken during pregnancy & early childhood Chelated by Ca+2 & deposited in newly formed teeth & Bone:
a. Teeth: Permanent yellow-brown discoloration & Enamel dysplasia.
b. Bone: Deformity & inhibition of growth.
11- Explain why doxycycline is allowed in patients with renal impairment.
Because it is excreted in bile.
12- Give reason aminoglycosides is not effective against Anaerobes.
Aminoglycosides concentrate inside bacteria by O2-requiring active transport mechanism. NOT effective against Anaerobes.
13- Give reason loop diuretics (frusemide) and aminoglycosides are not preferable combinations.
Ototoxicity and nephrotoxicity is increased when this combination is used
14- Give reason Trimethoprim and Sulfamethoxazole are combined to form Co- trimoxazole.
More potent, wider spectrum & less bacterial resistance than each drug alone
15- Give reason in TB drug combinations are used.
a. ↑ Activity.
b. ↓ Toxicity.
c. ↓ Resistance.
16- Give reason vitamin B6 is given with Isoniazid.
↑ I.N.H. → Peripheral neuritis.
Prevented by Vit B6.
After I.V. glucose administration , the veins are flushed with saline
To avoid thrombosis & sclerosis .
Patient are advised to change site of insulin injection:
To avoid subcutaneous lipodystrophy
Patient are advised to reduce evening insulin dose:
To avoid Somogyi effect, which is :
Rebound hyperglycemia in the morning , that follows insulin – induced hypoglycemia during night.
Sulfonylurea are not indicated for patient with sever pancreatitis :
This is because , the main act of sulfonylurea is to increase insulin release from pancreas , and that depend on presence of preformed endogenous insulin
Glyburide is not recommended for patient with creatinine clearance less than 50ml/min:
As it’s most likely to accumulate during renal dysfunction & cause hypoglycemia.
A hypoglycemic patient on acarbose , is advised to take glucose & not sucrose:
As acarbose is α-glucosidase inhibitor , it inhibits absorption of complex carbs as sucros
Escape phenomenon , in case of aldosterone excess:
prolonged hypervolemia to decrease sensitivity of DCT to aldosterone –>no Na & water retention but still K+ execration
Cortisol may be described as the deceiver:
As it treats the manifestation rather than the cause
cortisol is C.I with Digitalis toxicity:
due to hypokalemia resulting from cortisol, which worsens digitalis toxicity
prednisone is safe in pregnancy:
as it’s a prodrug that is not converted to active metabolite (prednisolone ) in the fetal liver –> no effect on fetus
chronically elevated P.T.H will deplete bone store of Ca2+ however, PTH ( teriparatide) is used in the ttt of osteoporosis :
as intermittent exposure to PTH will activate osteoblast more than osteoclast, with a net effect of: + new bone formation& bone mineral density
patient should remain upright for 30min after an oral Bisphosphonate dose:
to minimize esophageal irritation risk
natural estrogens have low bioavailability, however, semisynthetic estrogens -as: (ethinyl estradiol) could be taken orally:
because ethinyl group protect it from in activate by liver
it’s recommended to add progestogens to estrogen, while treating postmenopausal hormonal therapy (HT):
to reduce risk of endometrial carcinoma
oral progestogens only contraception is less effective than the combined method:
as missing a dose may lead to conception
advantage of benzodiazepine over Barbiturate:
- less REM —> less hangover& less rebound paradoxical sleep
- no HME induction –>less tolerance, dependance& interaction
- wide safety margin —> safer on R.C & C.V.S.
advantage of fluoxetine (SSRI) over (TCA)
- less adverse effect: .no atropine-like effect (safe in glaucoma)
no CVS AEs
no weight gain
- low acute toxicity: no cardio or hepato-toxicity
Advantage of direct dopamine agonist over L- DOPA:
- Does not need synthesizing enzyme& more specific on D2
- Longer T1/2 less fluctuation in response
- No toxic oxidative metabolite
Patient are advised to take urine alkalinization & plenty of fluid with probenecid
To avoid the formation of renal urate stone
colchicine or NSAID is affect prophylacticaIly with allopurinol:
As allopurinol precipitate acute attacks of gout during initiation of treatment
O2 is given during recovery from nitrous oxide anesthesia:
As N2O produce a diffusion hypoxia during recovery
Diazepam is given during recovery from ketamine:
To control dreams& terrifying hallucination during recovery
Ketamine or halothane are useful in bronchial asthma, while thiopentone is not:
As ketamine or halothane —-> bronchodilator
While, thiopentone —> cough, laryngospasm& bronchospasm
Morphine is contraindicated in asthmatic patient
As it’s produce bronchospasm by it’s direct spasmogenic effect & by increase histamine release
tolerance occur with morphine:
Due to decrease endogenous endorphin
morphine is used in primary neurogenic shock:
As it decrease pain that trigger autonomic manifestation, worsening the condition
morphine is contraindicated in head injury:
- Miosis -> interfere with diagnosis
- decrease R.C. -> increase CO2-> cerebral V.D increase CSF synthesis–> increase intra-cranial tension -> more decrease on R.C
meperidine + MAOI sever inhibition of R.C, excitation& seizure:
As meperidine decrease neuronal uptake of serotonin& nor adrenalin
meperidine is used in obstetric analgesia:
Due to less inhibition of fetal R.C. —-> less neonatal asphyxia
Fentanyl + Droperidol [neurolept-analgesia] is a good combination :
As the emetic effect of fentanyl is countered by antiemetic effect of droperidol
Hyperthermia in salicylate toxicity:
Due to uncoupling of oxidative-phosphorylation
toxic dose of aspirin in children may produce metabolic acidosis :
Due to impaired CHO metabolism
Aminoglycosides & fluroquinolone may be given in higher, less frequent daily, even once daily:
As both are antibiotic with concentration-dependent killing and/or strong post-antibiotic effect
B-lactams total daily dose may be divided over multiple dose or even by I.V. infusion:
As B-lactams are mainly time-dependent antibiotic
Culture sample is taken before starting empiric therapy:
To avoid interference with the culture result
Broad-spectrum antibiotic may be needed initially:
Needed for serious infection when:
1- identity of the organism is unknown
2- site of infection makes a polymicrobial likely
Duration of prophylactic antibiotic should be closely observed:
To prevent the unnecessary development of antibiotic resistance
Ampicillin & DicloxaciIlin are better taken l hr before meal or 2hr after meal:
As they are usually affected by meal
B-lactamase inhibitors are called suicide substrates:
As they bind with the enzyme& irreversibly inhibit it
Appearance of skin rash on a Patient after taking ampicillin:
As ampicillin induce skin rash in 10% of patient& In all patient with:
mononucleosis[EBV], leukemia& allopurinol
Lidocaine may be added with Benzathine penicillin and cephalosporins :
As they cause pain to site of injection
patient on cefoxitin for gynecological infection are advised to stay away from alcohol:
Due to Disulfiram like reaction induced by cefoxitin with alcohol
Patient on cefoxitin, cefoperazone or cefamandole are advised to take VIT. K l0 mg twice weekly:
To prevent hypoprothrombinemia induced by them
Celastatin is given with Imipenem:
As Imipenem is inactivated by renal tubular dihydropeptidase enzyme, giving a nephrotoxic metabolite
- So, celastatin is Co-administered to inhibit dihydropeptidase enzyme
patient on tetracycline are adviced not to take milky product with their dose of antibiotic:
As absorption of tetracycline is decreased by milk leading to chelation of tetracycline
Aminoglycosides are poorly absorbed from the intestine:
Because of there higher polar nature.so, if given orally, there effect will be restricted to only GIT
FDA had to issue a block box warning against Tigecycline:
As tigecycline was associated with a small but significant increase in the risk of death, so it should be reserved for situations where alternative ttt, are not suitable
1 inezolid is contraindicated with patient taking MAOI or within 2 weeks of taking MAOI:
As it may have drug interaction that lead to serotonin syndrome
NSAIDs are avoided with Fluoroquinolone, especially in epileptic:
As fluroquinolone induce seizures, especially if used with NSAIDs
Fluoroquinolone are avoided with elderly on glucocorticoids:
As it may cause rupture of tendons [ Achilles tendon]
Fluoroquinolone are adviced not to be taken along with food or other drugs, as : Sucralfate& antiacid:
As they decrease the absorption of fluoroquinolone
Patient on Sulfonamide are adviced to take plenty of fluid& urine alkalinization:
As sulfonamides are excreted & concentrated in urine, so it may produce crystalluria
Even thought sulfonamides decrease folic acids, but they have no effects on mammalian cells:
As mammalian cells use preformed folic acid
Sulfonamide are avoided during pregnancy & lactation:
As they are bound to plasma proteins—>displace bilirubin —-> kernicterus
Rifampicin can cause failure of contraception:
As it increase same enzymes that metabolize contraceptive pill
Sulfonamide can cause phenytoin toxicity:
As it decrease enzymes that metabolize phenytoin
Clarithromycin increase risk of rhabdomyolysis:
As it decreases enzymes that metabolize Simvastatin
Rifampicin cause withdrawal manifestation whin given to patient, whom are being treated from morphine addiction:
As Rifampicin is a HME inducer, which increase metabolism of Methadone used in ttt of Morphine addicts by substituting it…
Normal saline infusion is administered with the daily dose of Amphotericin B:
In order to attenuate the nephrotoxic cumulative adverse effect of amphotericin B
Developmental of new lipid drug formulation with amphotericin B :
To reduce toxicity as it bind to mammalian membrane less readily permitting the use of effective doses of the drug with lower toxicity
Flucytosine has a selective toxicity against fungi only:
As human cells are unable to convert the parent drug to its active metabolite
Combination of flucytosine with amphotericin B may by synergistic:
Due to enhanced penetration of flucytosine through amphotericin B damaged fungal cell membrane
Azol has a selective toxicity against fungi:
Due to their greater affinity for fungal than for human cytochrome P450 enzyme
Despite that fluoroquinolone are often advised not to be taken with food or antiacid, Itraconazole are recommended along with food or low gastric HCL
Itraconazole’s absorption from capsule is increased by food &low gastric PH
On prescribing Voriconazole to a hyperlipidemic patient on statins, doctor chose to reduce statin dose:
This is because Voriconazole is an inhibitor of mammalian CYP 3A4, required in the metabolism of HMG-CoA reductase inhibitor
Co-administration antihistamine with anidulafungin might be needed in the some cases:
This is in order to antagonize the increase amount of histamine released by anidulafungin
Griseofulvin id administered for 2-6 weeks for skin& hair infection:
- To allow the replacement of infected keratin by the resistant one
- As its is action to prevent infection of these new skin structure
- By depositing in newly forming skin, where it binds to keratin , protecting the skin from new infection
Co-administration of Griseofulvin with fatty food:
As its absorption is increased whin given with fatty food
