Drug interactions & unique SE Flashcards
Cyp450 inducers
decrease metabolism of other drugs leading to requiring modified doses
E.g. Phyntoin,phenobarbital,st.John’s, carbamazapine, Rifampin
cyp450 inhibitors
Ketoconazaole, Quinidine
Most common disease interaction seen with Chlorphenarmin/phenylephrine
BPH
Mechanism:
Sympathomimetic agents may cause or worsen urinary difficulty in patients with prostate enlargement due to smooth muscle contraction in the bladder neck via stimulation of alpha-1 adrenergic receptors.
Grey baby syndrome caused by:
Chloramphenicol
Gray man syndrome caused by:
Amiodarone
Red Man syndrome:
Vancomycin
Purple toe syndrome:
Warfarin
visual impairment is associated with which anti-TB drugs?
Ethambutol
Burning sensation in the feet is associated with which anti-TB?
Isoniazid
metallic taste is associated with:
Metformin & metronidazole
loss of taste is associated with:
Captopril
The action of digoxin can be reduced with:
Antacids and hyperhtyrodism, hyperkalemia
Process require CYP450:
Oxidation
Adsorption
irreversible chemical property
Which of the following decrease gastric emptying rate:
hypothyrodism, Atropine
Sulfahydryl-group related complications such as: rash, taste abnormalities, nephrotic syndrome is associated with:
Captopril (This is why max dose is limited to 100-150mg/day)
Inducers of P-gp
inducers of P-gp drug efflux may decrease serum concentrations of substrates of P-gp.
Phenytoin
Carbamazepine
Rifampin (rifampicin)
Inhibitors of P-gp
Inhibitors of the P-gp drug efflux pump (also known as P-gp multidrug resistance transporter) : increase serum concentrations of drugs that are substrates of P-gp
Amiodarone, Carvedilol
Azithromycin, Clarithromycin
Ketoconazole (systemic), Itraconazole
Verapamil, Quinidine, Ranolazine
Mechanism of drug interaction between Nitrates and PDE-5 inhibitors:
both Nitrate inhibit the enzyme Guanylyl Cyclase which is responsible for transforming GTP to cGMP thus causing vasodilation smooth muscles and PDE5 inhibitors inhibit the degradation of cGMP by PED-5 enzyme which lead to accumulation cGMP leading to profound relaxation of smooth muscles, dangerous hypotension and decreased perfusion to critical organs.
If a patient who has taken a phosphodiesterase-5 inhibitor for erectile dysfunction develops chest pain, delay nitrate therapy for…………… hours after taking avanafil, …………….. hours after taking sildenafil or vardenafil, and ……………..hours after taking tadalafil.
If a patient who has taken a phosphodiesterase-5 inhibitor for erectile dysfunction develops chest pain, delay nitrate therapy for ≥12 hours after taking avanafil, ≥24 hours after taking sildenafil or vardenafil, and ≥48 hours after taking tadalafil.
Luminous phenomena due to the fact that in the Retina of the eye there are If channels, bradycardia, AV block, Afib are SE associated with:
Ivabradine (PROCORALAN): Atnti-anginal
Managing peripheral edema caused by CCB particularly with Dihydro
The peripheral edema is related to redistribution of fluid from the vascular space into the interstitium. In theory, increased calcium channel blocker-mediated vasodilation leads to increased pressure and subsequent permeability in the capillary circulation The risk of edema is more common with dihydropyridines than with non-dihydropyridines and appears to be dose dependent.
Calcium channel blocker-mediated edema may prompt clinicians to prescribe diuretics, especially loop diuretics, which increase polypharmacy and may cause harm in patients without hypervolemia. However, since calcium channel blocker-mediated edema is not the result of increased plasma volume, it tends not to improve with diuretic therapy. Conversely, addition of an inhibitor of the renin-angiotensin system (RAS), either an angiotensin-converting enzyme (ACE) inhibitor, an angiotensin receptor blocker (ARB), or a direct renin inhibitor can significantly reduce the incidence and severity of edema caused by calcium channel blockers. This effect is probably related to ACE inhibitor- or ARB-mediated venodilation that helps to reduce transcapillary pressure.
As such, edema caused by dihydropyridine calcium channel blockers can be treated by any combination of the following: reduction in dose, switch to a non-dihydropyridine agent, and/or addition of a RAS-blocking agent.
SE of nitrates:
Toxicity led by production of methmeglobinemia which can be reverted by the antidote: Methylene blue
Headache “Throbbing”: advice patient to take analgesics during first week.
Tachycardia (Marked) due to baroreceptors compensatory reflexes. Decrease dose gradually especially with continuous IV infusions.
Postural hypotension (due to venodialator effects of nitrates) avoid abrupt postural changes such as standing abruptly.
Amyl nitrite: inhaled nitrates
Significant SE of nitrates:
Methemoglobinemia: a blood disorder in which the hemoglobin can carry oxygen, but is not able to release it effectively to body tissues.can be acquired or inherited.
Antidote: Methylene blue is a specific treatment for nitrite toxicity. It causes a rapid conversion of methemoglobin to hemoglobin.
