The absorption of gabapentin following high dose escalation.

Gabapentins (GBP) is structurally similar to GABA yet its mode of action remains uncertain. It is water-soluble and GI tract absorption occurs via the L-amino acid transport system in the proximal small bowel. It has been suggested that this transportation is capacity limited, thus decreasing GBP bioavailability at higher doses. GBP is not protein bound, therefore, salivary levels might be expected to be similar to those in serum; also the drug does not induce hepatic enzymes and is excreted unmetabolised by the kidney. Within the dose-range normally prescribed, it is devoid of pharmacokinetic (PK) drug interactions with all other anti-epileptic drugs. This study assesses two things in patients with epilepsy: (a) bioavailability of higher doses of GBP (1200-4800 mg per day), and (b) the influence of high dose GBP on between-dose serum concentrations of co-prescribed anti-epileptic drugs. After stabilising at each dosage, a sequence of serum and saliva samples were collected within the dosage interval; GBP and co-medication concentrations were determined and the results subjected to PK modelling. Meaned results from 10 patients indicate that GBP continues to be absorbed in a reasonably linear manner relative to dose up to 4800 mg per day. The study also shows that GBP is transported into saliva, however, salivary concentrations are only 5-10% of those in plasma. Furthermore, the results indicate that GBP, in higher than recommended doses, did not change plasma concentrations of lamotrigine, carbamazepine, carbamazepine-epoxide, vigabatrin, primidone, phenobarbitone or phenytoin when added to treatment. It is concluded that larger than recommended doses of GBP can be efficiently absorbed by some patients and also that GBP plasma levels do not fluctuate greatly between dosage intervals, therefore, twice daily dosage is a possibility.

Salicylate intolerance: a masquerader of multiple adverse drug reactions.

A female in her early 50s presented with a long-standing history of episodic urticaria and angioedema. She also reported urticarial reactions after ingestion of aspirin, prednisone and multiple antibiotics. These medications were all taken during upper respiratory tract infections. An elimination diet followed by a series of open challenges to food chemicals demonstrated an urticarial eruption following the ingestion of mints, which contain high levels of salicylates. A double-blinded placebo-controlled challenge to salicylate confirmed her sensitivity and explained her reaction to aspirin. The patient informed her treating physician of her copious ingestion of mints during upper respiratory tract infections. Drug hypersensitivity to antibiotics and prednisone was excluded on the basis of negative radioallergosorbent tests (RASTs) and/or absent skin-test responses and/or tolerance to oral challenges. This patient had a salicylate intolerance that caused her episodic urticaria and angioedema, and also masqueraded as a drug allergy due to the concurrent ingestion of mints.

An association between tick bite reactions and red meat allergy in humans.

Twenty-five patients living in a tick-endemic region of Sydney, New South Wales developed red meat allergy after experiencing large local reactions to tick bites. This represents a potentially novel cross-reaction between an arthropod and a food protein. (MJA 2009; 190: 510-511).