Primidone interaction

Primidone Some problems associated with kidney functions are reported with primidone overdose. Primidone interacts with barbiturates and other antiepileptics.197... 

Clobazam Phenytoin Primidone Interaction inconsistent, usually of no clinical significance Unknown... 

Acetazolamide Primidone Interaction probably of little clinical significance Possibly reduced absorption of primidone... 

Garrettson LK, Gomez M. Phenytoin-primidone interaction. BrJ Clin Pharmacol (1977) 4, 693-5. 

Phenobarbital is a recognised potent liver eiKyme inducer that increases the metabolism of corticosteroids, thereby reducing their effects. Pharmacokinetic studies have shown that phenobarbital reduces the half-lives of these corticosteroids and increases their clearances by 40 to 209%. Primidone interacts in a similar way because it is metabolised in the body to phenobarbital. ... 

Drugs that may interact with carbonic anhydrase inhibitors include cyclosporine, primidone, salicylates, and diflunisal. 

Carbamazepine also can induce the enzymes that metabolize other anticonvulsant drugs, including phenytoin, primidone, phenobarbital, valproic acid, clonazepam, and ethosuximide, and metabolism of other drugs the patient may be taking. Similarly, other drugs may induce metabolism of carbamazepine the end result is the same as for autoinduction, and the dose of carbamazepine must be readjusted. A common drug-drug interaction is between carbamazepine and the macrolide antibiotics erythromycin and trolean-domycin. After a few days of antibiotic therapy, symptoms of carbamazepine toxicity develop this is readily reversible if either the antibiotic or carbamazepine is discontinued. 

Geriatric Considerations - Summary Primidone is poorly tolerated in older adults avoid use if possible. Dosage adjustments are required in renal impairment. Numerous drug interactions with primidone exist. Primidone may reduce bone mineral den-sitybyinterferingwith vitamin D catabolism. Calcium and vitamin D supplementation and monitoring of bone mineral density are recommended for older adults taking this drug. 

CBZ stimulates the CYP-450 enzyme system, increasing clearance of concomitantly prescribed drugs also metabolized by this system ( 377). Thus, the dose of these medications may need to be increased to maintain efficacy (372). Levels of CBZ may also be influenced by other hepatically metabolized, co-prescribed drugs. VPA, isonicotine, hydrazine, and erythromycin are some of the agents that can increase CBZ levels, while agents such as phenytoin and primidone can lower them. Table 10-25 summarizes the potentially clinically significant interactions between CBZ and other commonly co-prescribed medications ( 379, 380). 

Primidone Similar to phenytoin but converted to phenobarbital Well absorbed orally not highly bound to plasma proteins peak concentrations in 2-6 h t /2 10-25 h two active metabolites (phenobarbital and phenylethylmalonamide) Generalized tonic-clonic seizures, partial seizures Toxicity Sedation, cognitive issues, ataxia, hyperactivity Interactions Similar to phenobarbital... 

Levetiracetam Action on synaptic protein SV2A Well absorbed orally not bound to plasma proteins metabolized to 3 inactive metabolites ty2 6-11 h Generalized tonic-clonic seizures, partial seizures, generalized seizures Toxicity Nervousness, dizziness, depression, seizures Interactions Phenobarbital, phenytoin, carbamazepine, primidone... 

Corticosteroids interact with barbiturates, carbamazepine, phenytoin, primidone, frusemide, thiazide, NSAIDs, antidiabetics, and antihypertensive drugs. Benzquinamide hydrochloride is incompatible with chlordiazepoxide, diazepam, and some barbiturates. Care should be exercised when handling bisacodyl to avoid contact with skin and mucosal membranes. 

Drug interactions involving AEDs are shown in Table 52-5. Phenobarbital, phoiytom, primidone and carbamazepine are potent inducers of cytochrome P450 (CYP450), epoxide hydrolase, and uridine diphosphate gjucuronosyltransferase enzyme systems. Valproic acid inhibits many hepatic enzjrme systems and displaces some drugs from plasma albumin. Felbamate and topiramate can act as inducers with some isoforms and inhibitors with others. 

BARBITURATES FLUCONAZOLE, ITRACONAZOLE, KETOCONAZOLE, VORICONAZOLE 1 azole levels with risk of therapeutic failure Barbiturates induce CYP3A4, which metabolizes itraconazole and the active metabolite of itraconazole. Primidone is metabolized to phenobarbitone Watch for inadequate therapeutic effects and t dose of azole if effect due to interaction... 

Clobazam Carbamazepine Primidone Valproate Phenytoin Interaction inconsistent, usually of little clinical significance Inhibition of metabolism of the object drug... 

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