Clinically reported drug interactions with Erythromycin-an update

Erythromycin, the prototypical macrolide, has been widely used since 1950s in the management of infections. It is often combined with other drug therapies, thus creating a potential for pharmacokinetic interactions. It can both inhibit drug metabolism in the liver by complex formation and inactivation of microsomal drug oxidizing enzymes, and also by interfering with microorganisms of the enteric flora through its antibiotic effects. Methodology: Using MEDLINE search [1975-April 2002] all available clinical studies, review articles, and case reports were reviewed to provide an unbiased account of drug interactions with erythromycin. A number of reports and controlled studies have incriminated erythromycin as a potential source of clinically severe drug interactions. For example torsades de pointes associated with QT prolongation occurred with terfenadine, astemizole, and cisapride. Cases of rhabdomyolysis have been reported on concomitant use of statins. Symptomatic hypotension occurred with calcium channel blockers or sildenafil. Excessive sedation occurred from concurrent use of benzodiazepines, buspirone and zopiclone. Ataxia occurred with carbamazepine and valproate, and ergotism with ergotamine. Serotonin syndrome was reported with the use of sertraline and psychosis with bromocriptine. Interactions with cyclosporine, tacrolimus, theophylline, and warfarin are also clinically important. These interactions are due to decreased clearance of these drugs. Increase in digoxin concentration was mainly due to increase in bioavailability. Erythromycin should, therefore, be not administered with some of these drugs or their dosage schedule readjusted. Conclusions: In most cases, the extent of drug interaction varies widely among individuals; this is likely dependent on interindividual differences in CYP3A4 tissue content, preexisting medical conditions and possibly, age. Interactions may occur under single dose conditions or only at steady state. The pharmacodynamic consequences may or may not closely follow pharmacokinetic changes. Drug interactions may be most important when patients are stabilized on the affected drug and erythromycin is then administered

Empirical treatment of uncomplicated urinary tract infection by community pharmacist in the Eastern Province of Saudi Arabia

It is a well known phenomenon in the Kingdom of Saudi Arabia that prescription drugs are dispensed over the counter in the community pharmacies. The aim of this study is to document the attitude of community pharmacists to fulfill the concept of pharmaceutical care and to evaluate how they manage a case of acute uncomplicated lower urinary tract infection. Eighty-eight community pharmacists in the Eastern province of Saudi Arabia were presented with a patient claiming urinary tract infection and seeking medical treatment. Only one attendant pharmacist refused to dispense medications without prescription. Fifteen others [17%] dispensed urinary antiseptic only and 72 [82%] gave antibacterial agents. Fluoroquinolones were the most commonly dispensed [69%] as first choice and 87% as an alternative] followed by co-trimoxazole, penicillins, cephalosporins and tetracyclines. The number of drugs dispensed ranged from a single agent at 52 [59%], 2 drugs at 31 [35%] and 3 drugs at 4 [4.5%] pharmacies. The average cost was Saudi Riyal [SR] 45.8 [$12.2] for first choice drugs and SR 31.5 [$ 8.4] for the alternatives. The heavy dispensing of fluoroquinolones over the counter could eventually lead to increased resistance of the pathogenic bacteria to these drugs. However, despite the lack of pharmacist's adherence to the pharmaceutical law, this study does not indicate that they had abused their patients. It is rather demonstrating the urgent needs for successful implementation of the pharmaceutical law taking into consideration better integration between governmental health providers and the private retail pharmacies. In addition, it supports calls to educate pharmacists to perform basic clinical assessment in the community pharmacy, as a vital tool to effectively manage their patients' health status. The Ministry of health should credit such educational activity for the renewal of pharmacist's license in the Kingdom

Utilization of digoxin and theophylline assays in the eastern province

The utilization of therapeutic drug monitoring [TDM] for serum digoxin and theophylline was assessed with respect to the indication, time of sample collection and contribution to patient care. A total of 585 serum drug level determinations of digoxin [275] and theophylline [328] were done in a four month period. Reasons for requests were subtherapeutic response [27.5%], suspected toxicity [3.8%], baseline data [26.7%], patients at risk for toxicity [7.7%], and for the remaining 34.4% of orders, no reason was stated. The highest number of requests 246 [42.1%] were from the inpatient ward [INP], followed by emergency room [ER] 32.6%, outpatient department [OPD] 13% and intensive care unit [ICU] 12.3%. Repeated assays accounted for 363 determinations of which 55.9% had levels similar to the previous ones. In this study, we found a high incidence of inappropriateness in patient selection [34.4%], time of serum sample collection [28.4%], and dosage adjustment [46.8%]. However, when these audit criteria were analyzed together, the overall appropriateness was as low as 33.5%. This indicated that serum drug monitoring was poorly utilized and did not contribute much to the patient's care. This results in an estimated financial loss per year [for inappropriate use of digoxin and theophylline levels] of about 37,344 Saudi Riyals [US $ 9,956.00]. Corrective educational programs for the staff, based on standard guidelines for TDM, have been initiated and this study is a baseline for future prospective audits