The Importance of Prescription Medication

In addition, counterfeit PDE-5i often contain contaminants. These are used either as bulking agents to lower production costs or to imitate the appearance and physical qualities of the genuine product. In those samples seized in the United Kingdom, Italy, and Indonesia, there were contaminants such as gypsum, non-purified talc, amphetamine, commercial grade paints, paracetamol, and metronidazole (27,28,30). These non-pharmaceutical ingredients can have toxicities of their own. Non-declared pharmaceuticals can have drug interactions and side effects such as gastrointestinal symptoms and nausea when combining metronidazole and alcohol. Counterfeiters do not declare these ingredients or warnings of possible deleterious interactions on their packaging. Furthermore, the manufacturing conditions of counterfeiters cannot match the sterile processing conditions of legitimate pharmaceuticals. In an analysis of microbial loads of various illicit ED drugs, 23% were contaminated with more than 103 colony-forming units (CFU), and 69% had elevated levels considered within acceptable limits. Not a single CFU was detected in any of the approved PDE-5i obtained legally (29) (Figure 1). These results are not surprising, when considering the strict regulations and inspections that legitimate pharmaceutical producers must pass, compared with the unsterile conditions in which counterfeiters may work. Many laboratories of counterfeiters are exposed to the open air and use unsterile water that would not be safe for drinking. Contamination with either adulterants or bacteria poses risks to consumers of counterfeit PDE-5i. Perhaps even more dangerous than the counterfeit PDE-5i that is marketed as legitimate pharmaceuticals, however, are those marketed as “natural” supplements.

Important Medical Note

Examples of commonly prescribed medications that have interactions with PDE-5i are included in Table 1. Before PDE-5i are prescribed, patients must be evaluated for potential drug interactions and warned of the absolute contra-indications. There is also an indirect risk of missing potential medical conditions in patients that bypass the healthcare system to purchase illicit PDE-5i. It has been well documented that ED is associated with significant medical comorbidities including cardiovascular disease, diabetes, metabolic syndrome, hypertension, and hyperlipidemia (23). The Second Princeton Consensus on sexual dysfunction and cardiac risk stated that all men with ED, even in the absence of manifesting cardiac symptoms should be regarded as having potential risks for cardiovascular disease (24). Unlike pharmaceuticals requiring prescriptions, there is little Food and Drug Administration (FDA) regulation of health supplements. As a result, many so-called “natural” supplements, in fact, contain active ingredients of prescription strength drugs that could be potentially harmful. In a well-known example, 150 non-diabetic patients were hospitalized with hypoglycemia in Singapore. Seven patients fell into a comatose state, and four subsequently died. The common link between these patients was the use of an ED supplement that contained glyburide (a sulfonylurea used to treat diabetes), as well as illicit PDE-5i (31). In one study, the ingredients of 58 products available for the treatment of ED without a prescription were analyzed.

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There is no current pharmacologic antidote to these interactions (21). Other side effects include headache, dyspepsia, flushing, myalgia/back pain, visual disturbances, and nasal congestion. Many of these side effects occur because there is cross-reaction with other phosphodiesterase types located throughout the body (18,22). PDE-5i are metabolized almost exclusively by the cytochrome P 450 system in the liver, specifically Cytochrome P4503A. Concurrent use of CYP 3A inhibitors or inducers can significantly alter the concentration of serum PDE-5i changing the side-effect profile, effectiveness of the medication, or severity of drug interactions (21). Even though 57 of 58 products were labeled as “all natural” and no sample claimed to include synthetic substances, 81% contained PDE-5i. Several contained higher-than-approved amounts of PDE-5i, and others contained PDE-5i analogs that are not approved for use. One even contained phentolamine, an alpha-blocker, with which concurrent use with PDE-5i is contraindicated.

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In 2009, United Kingdom authorities seized 2,383 samples of counterfeit Viagra and forwarded them to Pfizer laboratories for analysis. The concentration of active sildenafil ranged from 0–200% of indicated strength, and only 10% of the samples contained an active ingredient within 10% of what was advertised on the packaging (27). Similar results were found in an analysis of counterfeit ED drugs sold in Italy, Austria, and Canada (28). These problems are magnified in developing countries with less regulation. In Indonesia, 100% of “Viagra” sold by street peddlers, 56% purchased in “drug stores”, and 13% acquired from legitimate pharmacies was counterfeit Viagra marked as authentic (29). Packaging and labeling were inadequate, and only 14 samples warned against concomitant nitrate use, a potentially fatal drug interaction (32). Recently, in January of 2016, the FDA announced warnings against 40 products marketed as dietary supplements that contained undeclared PDE-5i (33) (Table 3). Unsuspecting patients often seek alternative treatments of ED due to embarrassment and lower cost, but also because of the perception that “all natural” products are somehow safer than synthetic medications. However, by doing so, many of these patients are unknowingly subjecting themselves to significant health dangers.

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Currently, evidence suggests that ED is not only correlated with cardiovascular disease due to shared medical comorbidities, but is, in fact, an independent risk factor for cardiovascular disease. Thus, all men with vasculogenic ED should undergo cardiac risk stratification and risk factor management (25). In an analysis of 24,708 patients receiving a PDE-5i, 70% had an underlying medical diagnosis, with 50% of these patients having vasculogenic disease. Furthermore, 11.5% of patients being evaluated for a PDE-5i prescription had a new underlying disease detected (26). The most detrimental problem with counterfeit PDE-5i is that the content is unregulated. Strategies to limit counterfeiting should be multi-faceted and target prescribing healthcare professionals, pharmaceutical companies, regulatory authorities, and patients. As such, in 2006, the WHO created a global coalition of stakeholders called International Medical Products Anti-Counterfeiting Taskforce (IMPACT), which aims to build coordinated networks across and between countries in order to halt the production, trading, and selling of fake medicines around the globe (34). Similarly, PDE-5i manufacturers have started working with regulatory and law enforcement authorities, as well as providing distinctive packaging using holographic security foil, 2D barcodes, and radio frequency identification (RFID) tags. The problem with RFID is the unfunded cost of implementation that has been estimated to range from $84,000 for individual pharmacies to $1.3 billion for large-chain pharmacies and may present significant barriers to RFID adoption (35). Similarly, the FDA has launched significant public education campaigns through magazine public service announcements, education leaflets, news articles, a consumer website ( and a pharmacist education program (36). Finally, it is the healthcare provider’s responsibility to continue to support efforts to maintain consumer access to potency drugs, educate patients on the risks of counterfeit and other non-FDA approved products, remind them to only purchase from a VIPPS-certified pharmacy if they want to fill their prescription online, and report any suspected cases of counterfeit medicines to the FDA (37). Counterfeit PDE-5i pose many—possibly serious—risks to patients. As the population ages, and the market for PDE-5i grow, so does the illicit market for PDE-5i. Counterfeit PDE-5i have become a worldwide problem that comprises a large percentage of PDE-5i use in both developing and well-developed countries. Patients embarrassed by their condition or seeking less expensive alternatives to legitimate pharmaceuticals have fueled the market, and the growth of Internet pharmaceuticals have made counterfeit pharmaceuticals easy to obtain. However, ED is a medical condition that needs to be treated as such. By bypassing the legitimate healthcare system, users of counterfeit PDE-5i bypass screening for concurrent medical comorbidities, as well as proper education and warnings of PDE-5i use.

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In pills marked as 100 mg, 64% contained <50 mg, 25.5% contained between 50–95 mg, and only 4.7% contained between 95 to 105 mg; 5.7% contained >105 mg (30). Quantities of active ingredients are also highly variable, as seen in Table 2. The effects of widely variable amounts of active ingredient range from low efficacy at a minimum to severe side effects and negative drug interactions at the worst. As stated, counterfeit PDE-5i rarely are packaged with the appropriate warning labels. PDE-5i products purchased from Internet pharmacies rarely contain the stated amount of active ingredient (17). Furthermore, counterfeit PDE-5i often contain improper dosing and contaminants that may place patients at direct risk. Many “natural supplements” contain illicit PDE-5i, subjecting users to the same risks with even less warning. Physicians who treat ED should warn patients against purchasing PDE-5i via alternative means, especially the Internet. The use of dietary supplements for treatment of ED should be screened for and given due precautions. Conflicts of Interest: Dr. WJ Hellstrom has been an advisor or consultant to Pfizer. The other authors have no conflicts of interest to declare. J Sex Med 2011;8:1-3. 10.2515/therapie/2015031 [DOI] [PubMed] [Google Scholar] 10.1136/bmj.39412.431655.AD [DOI] [PMC free article] [PubMed] [Google Scholar] 8.Jackson G, Arver S, Banks I, et al.