Felodipine Theophylline

Drugs that may affect barbiturates include alcohol, charcoal, chloramphenicol, MAO inhibitors, rifampin, and valproic acid. Drugs that may be affected by barbiturates include acetaminophen, anticoagulants, beta blockers, carbamazepine, chloramphenicol, clonazepam, oral contraceptives, corticosteroids, digitoxin, doxorubicin, doxycycline, felodipine, fenoprofen, griseofulvin, hydantoins, methoxyflurane, metronidazole, narcotics, phenmetrazine, phenylbutazone, quinidine, theophylline, and verapamil. 

Drugs that can decrease carbamazepine serum levels include charcoal, cisplatin, doxorubicin, felbamate, hydantoins, rifampin, phenobarbital, primidone, theophylline. The serum levels of oral contraceptives, haloperidol, bupropion, anticoagulants, felbamate, valproic acid, felodipine, tricyclic antidepressants, acetaminophen, ziprasidone, voriconazole, topiramate, tiagabine, olanzapine, and lamotrigine can be lowered by carbamazepine. 

Erythromycin Drugs that may be affected by erythromycin include alfentanil, anticoagulants, benzodiazepines, buspirone, carbamazepine, cisapride, cyclosporine, digoxin, disopyramide, ergot alkaloids, felodipine, fluoroquinolones, HMG-CoA reductase inhibitors, lincosamides, methylprednisolone, penicillins, and theophyllines. Drugs that may affect erythromycin include antacids, pimozide, rifamycins, and theophyllines. 

Phenobarbital Enhances phasic GABAa receptor responses reduces excitatory synaptic responses Nearly complete absorption not significantly bound to plasma proteins peak concentrations in Vi to 4 h no active metabolites tjy2 varies from 75 to 125 h Generalized tonic-clonic seizures, partial seizures, myoclonic seizures, generalized seizures, neonatal seizures, status epilepticus Toxicity Sedation, cognitive issues, ataxia, hyperactivity Interactions Valproate, carbamazepine, felbamate, phenytoin, cyclosporine, felodipine, lamotrigine, nifedipine, nimodipine, steroids, theophylline, verapamil, others... 

Antidepressants selective serotonin reuptake inhibitors, tricyclic antidepressants Antihypertensives felodipine Antibiotics quinolones, isoniazid Bronchodilators albuterol, theophylline Corticosteroids prednisone Dopa agonists levodopa Herbals ma huang, ginseng, ephedra Nonsteroidal anti-inflammatory drugs ibuprofen Stimulants amphetamines, methylphenidate, caffeine, cocaine Sympathomimetics pseudoephedrine Thyroid hormones levothyroxine Toxicity anticholinergics, antihistamines, digoxin Withdrawal alcohol, sedatives... 

II. BRONCHODIIATORS - montelukast, theophylline 12. CARDIAC GLYCOSIDES -digitoxin 13. CALCIUM CHANNEL BLOCKERS - felodipine, nifedipine, nimodipine, nisoldipine, verapamil... 

Giving calcium-channel blockers to patients taking theophylline normally has no adverse effect on the control of asthma, despite the small or modest alteration that may occur in serum theophylline levels with diltiazem, felodipine, nifedipine and verapamil. However, there are isolated case reports of unexplained theophylline toxicity in two patients given nifedipine and two patients given verapamiL Isradipine appears not to interact... 

In 10 healthy subjects felodipine 5 mg every 8 hours for 4 days reduced the plasma AUC of theophylline (given as theophylline aminopropanol Oxyphylline) by 18.3%, but had no effect on metabolic or renal clearance. ... 

It is believed that diltiazem and verapamil can, to a limited extent, decrease the metabolism of theophylline by the liver, possibly by inhibiting the cytochrome P450 isoenzyme CYP1A2. Similarly, nifedipine may alter hepatic theophylline metabolism, or it may increase the volume of distribution of theophylline. " Felodipine possibly reduces theophylline absorption. ... 

The evidence for this interaction is adequately documented but the results are not entirely consistent. However, the overall picture is that the concurrent use of theophylline and these calcium-channel blockers is normally safe. Despite the small or modest decreases in the clearance or absorption of theophylline seen with diltiazem, felodipine and verapamil, and the quite large reductions in serum levels seen in one study with nifedipine, no adverse changes in the control of the asthma were seen in any of the studies. However, very occasionally and unpredictably theophylline levels have risen enough to cause toxicity in patients given nifedipine (2 case reports) or verapamil (2 case reports), so that it would be prudent to be aware of the possibility of an interaction when these drugs are given. 

---