Dexamethasone Cimetidine

Praziquantel is readily absorbed (80% in 24 hours) after oral administration, with serum concentrations being maximal in 1 to 3 hours the drug has a half-life of 0.8 to 1.5 hours. Its bioavailability is reduced by pheny-toin or carbamazepine and increased by cimetidine. Dexamethasone decreases plasma praziquantel levels by 50%. Praziquantel is excreted by the kidneys. 

In vitro studies with human liver tissue suggest that no metabolic interactions are likely to occur between paclitaxel and cimetidine, dexamethasone or diphenhydramine. Cremophor may inhibit the intracellular uptake and metabolism of paclitaxel. 

On the basis of an in vitro study using human liver sliees and human liver mierosomes it has been coneluded that the metabolism of paclitaxel is unlikely to be altered by cimetidine, dexamethasone or diphenhydramine, all of which are frequently given to prevent the hypersensitivity reactions associated with paclitaxel or its vehicle, Cremophor (see b, below). The UK manufacturers say that paclitaxel clearance in patients is not affected by cimetidine premedication, although some authors have advised caution when using cimetidine with docetaxel or paclitaxel since cimetidine is known to affect the cytochrome P450 isoenzyme CYP3A4, which is responsible, in part, for the metabolism of these taxanes. 

P-gp (ABCB1) Verapamil, digoxin, mitoxantrone, vinblastine, doxorubicin, losartan, talinolol, cortisol, dexamethasone, colchicine, loperamide, domperidone, indinavir, erythromycin, tetracycline, itraconazole, cyclosporine, methotrexate, amitryptyline, phenobarbital, morphine, cimetidine, and others... 

Paclitaxel Peripheral neuropathy (DLT), nausea/vomiting, alopecia, hypersensitivity reactions Use caution with any elevation in AST (SGOT). Give proper dosing for liver dysfunction. Premedicate dexamethasone, diphenhydramine, and cimetidine. 

Figure 6.17 The classification of 42 drugs in the (solubility-dose ratio, apparent permeability) plane of the QBCS. The intersection of the dashed lines drawn at the cutoff points form the region of the borderline drugs. Key 1 acetyl salicylic acid 2 atenolol 3 caffeine 4 carbamazepine 5 chlorpheniramine 6 chlorothiazide 7 cimetidine 8 clonidine 9 corticosterone 10 desipramine 11 dexamethasone 12 diazepam 13 digoxin 14 diltiazem 15 disopyramide 16 furosemide 17 gancidovir 18 glycine 19 grizeofulvin 20 hydrochlorothiazide 21 hydrocortisone 22 ibuprofen 23 indomethacine 24 ketoprofen 25 mannitol 26 metoprolol 27 naproxen 28 panadiplon 29 phenytoin 30 piroxicam 31 propanolol 32 quinidine 33 ranitidine 34 salicylic acid 35 saquinavir 36 scopolamine 37 sulfasalazine 38 sulpiride 39 testosterone 40 theophylline 41 verapamil HC1 42 zidovudine.

Premedication, consisting of dexamethasone 20 mg intravenously, 12 and 6 hours before the infusion, and diphenhydramine 50 mg and cimetidine 300 mg, intravenously 30 minutes before the infusion, are now routinely given before patients are treated with paclitaxel, and this, as well as a recommended infusion time of 3 hours, has reduced the incidence and severity of hypersensitivity reactions. A single dose of dexamethasone 16 mg given 30 minutes before paclitaxel was effective in preventing hypersensitivity reactions in 43 patients (38) however, whether a single dose of a glucocorticoid is sufficient for prophylaxis is controversial. 

C It is recommended that all patients receiving paclitaxel receive pretreatment to reduce the risk and severity of hypersensitivity reactions. The preferred regimen includes a combination of a corticosteroid (such as dexamethasone), an antihistamine (diphenhydramine or equivalent), and an Hj antagonist (such as cimetidine or ranitidine). Omeprazole and other PPIs will not block Hj-receptor sites and do not provide protection against hypersensitivity reactions. 

Clinically important, potentially hazardous interactions with alfuzosin, alprazolam, amphotericin B, anisindione, antacids, aprepitant, astemizole, atorvastatin, bosentan, ciclesonide, cimetidine, clorazepate, conivaptan, cyproterone, dasatinib, dexamethasone, dicumarol, didanosine, eplerenone, erythromycin, ethotoin, fentanyl, fesoterodine, fosamprenavir, fosphenytoin, grapefruit juice, HMG-CoA reductase inhibitors, imatinib, ixabepilone, lapatinib, lopinavir, lovastatin, mephenytoin, methylprednisolone, micafungin, midazolam, nilotinib, pimozide, prednisolone, prednisone, quinidine, rifampin, rimonabant, rivaroxaban, sildenafil, silodosin, simvastatin, sirolimus, solifenacin, temsirolimus, terfenadine, tolvaptan, triazolam, vardenafil, vinblastine, vincristine, warfarin... 

Clinically important, potentially hazardous interactions with amprenavir, aprepitant, atazanavir, carbamazepine, chlorpheniramine, cimetidine, clarithromycin, clorazepate, CNS depressants, darunavir, delavirdine, dexamethasone, efavirenz, erythromycin, esomeprazole, fluconazole, fluoxetine, fosamprenavir, grapefruit juice, griseofulvin, imatinib, indinavir, itraconazole, ivermectin, ketoconazole, lopinavir, nelfinavir, nevirapine, phenobarbital, phenytoin, primidone, rifabutin, rifampin, ritonavir, roxithromycin, saquinavir, St John s wort, telithromycin, tipranavir... 

Clinically important, potentially hazardous interactions with amprenavir, aprepitant, bedomethasone, buprenorphine, calcium, chloramphenicol, cimetidine, dobazam, clorazepate, cyclosporine, cyproterone, darunavir, dasatinib, delavirdine, dexamethasone, diazoxide, disulfiram, dopamine, fesoterodine, fluconazole, flunisolide, fluoxetine, fosamprenavir, ginkgo biloba, hydrocortisone, imatinib, indinavir, influenza vaccines, isoniazid, isradipine, itraconazole, lacosamide, lapatinib, lopinavir, meperidine, methylprednisolone, midazolam, mivacurium, nelfinavir, nilotinib, nilutamide, phenylbutazone, piracetam, posaconazole, prednisolone, prednisone, primrose, ritonavir, rivaroxaban, sage, saquinavir, solifenacin, St John s wort, sucralfate, telithromycin, temsirolimus, teniposide, ticlopidine, tizanidine, tolvaptan, triamcinolone, uracil/tegafur, vigabatrin... 

Prepare and administer using glass or non-PVC IV bags and tubing Premedicate patients to prevent hypersensitivity reactions dexamethasone 20 mg IV or orally 12 hours and 6 hours prior to paclitaxel, and diphenhydramine 50 mg IV 30 minutes prior to paclitaxel, and ranitidine 50 mg IV or cimetidine 300 mg IV 30 minutes prior to paclitaxel Reduce dose in patients with elevated total bilirubin (>1.5 mg/dL) and/or elevated transaminases (guidelines not well established)... 

Also analyzed acepromazine, acetaminophen, acetophenazine, albuterol, aminophylline, amitriptyline, amobarbital, amoxapine, eunphettunine, amylocaine, antipyrine, aprobar-bital, aspirin, atenolol, atropine, avermectin, barbital, benzocaine, benzoic acid, benzotro-pine, benzphetamine, berberine, bibucaine, bromazepan, brompheniramine, buprenor-phine, buspirone, butabarbital, butacaine, butethal, caffeine, carbamazepine, carbromal, chloramphenicol, chlordiazepoxide, chloroquine, chlorothiazide, chloroxylenol, chlorphe-nesin, chlorpheniramine, chlorpromazine, chlorpropamide, chlortetracycline, cimetidine, cinchonidine, cinchonine, clenbuterol, clonazepam, clonixin, clorazepate, cocaine, codeine, colchicine, cortisone, coumarin, cyclazocine, cyclobenzaprine, cyclothiazide, cyheptamide, cymarin, danazol, danthron, dapsone, debrisoquine, desipramine, dexamethasone, dex-... 

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