This paper provides a qualitative description of the PO injection practices of young PWID in NYC. Qualitative interview findings reveal that PO injection often necessitates the use of 1.0 cc syringes or the administration of multiple injections with smaller syringes (0.5 cc) due to the additional water that is needed to dissolve extended-release and/or abuse-deterrent opioid pills in aqueous solution. These multi-step pill injection practices can increase the likelihood of sharing and cross-contaminating injection equipment, thereby increasing the risk of HIV [29] and HCV transmission [6, 28, 30]. Our findings corroborate results from other qualitative studies that describe the unique mechanics involved in preparing and injecting POs [8, 11]. By contrast, the mechanics required to prepare and inject heroin—particularly, the powder form of heroin that predominates in the Eastern part of the USA—are considerably less cumbersome, and consequently, intrinsically less risky. The nominal amount of residue that remains in cookers after episodes of heroin injection reduces the likelihood that PWID will be motivated to consume or share “rinse shots,” as was reported by study’s participants in reference to injecting POs, as well as by Bruneau et al. and Broz et al. [7, 11].

Quantitative results indicate that, in addition to injecting heroin, a majority of young PWID in our sample (59%) have also injected POs. The prevalence of PO injection, however, is considerably lower than the 75% reported by Bruneau et al. in Montreal and the 89% reported by Havens et al. in rural Appalachia [3, 7]. The lower prevalence of PO injection in our NYC sample might be explained by regional differences in drug markets. Heroin in NYC is widely available and significantly cheaper than diverted POs, allowing PWID to choose between POs and heroin based on their income-generating strategies and SES, whereas in Canada [29], heroin is available but more expensive than POs, and in certain rural areas of the USA, like Kentucky [3], heroin is difficult to access, which can necessitate more frequent PO injection, even in places where POs are exceedingly expensive (e.g., Scott County, Indiana).

Our qualitative findings illustrate how the preparation and injection practices associated with the parenteral administration of POs (e.g., multiple drug washes, reuse of drug paraphernalia containing drug residue, multiple injections per injection episode) place PWID at increased risk for blood-borne infection. Adjusted odds ratios from multivariable analysis indicate that participants who tested HCV antibody-positive had 2.3 times the odds of having injected POs than those who had never injected them. These results support similar findings reported in both urban [4, 7] and non-urban settings [3, 6]. Taken together, our research findings from NYC contribute to an emerging body of literature indicating that PO injection is independently associated with increased risk of HCV infection. This heightened risk may explain, in part, the sharp increase in acute HCV infections in many jurisdictions throughout the USA where PO injection is prevalent [31]. It also raises the possibility of an HIV outbreak driven by sharing injection paraphernalia other than syringes when PWID reinsert their own used needle into the cooker in preparation of multiple washes [32]. Additionally, to the extent that PO injection motivates PWID to re-use drug-residue-containing filters or cottons, it could potentially heighten risk for endocarditis, as damp filters provide an ideal breeding ground for bacteria.

In this paper, we also contrast patterns of heroin and PO injection among young adult PWID in NYC. In a drug market with a steady heroin supply, such as NYC, the preponderance of young PWID in this study initiated their opioid use with oral intake of POs at about 16 years old. Oral consumption of POs occurred for an average of 2–3 years prior to the first heroin use at age 19. Despite years of nonmedical PO use without heroin, a large majority of PWID (82%) chose heroin as their first injected drug. In sharp contrast to the reported 62% of PWID in rural Appalachia who initiated injection with POs [3], only 7% of young PWID in our sample chose POs as their first injected drug. This geographic variation may indicate that in areas where both heroin and POs are readily accessible, opioid users are far more likely to choose heroin instead of POs as the first drug they inject. This might also result from wanting to avoid the complicated hassle of preparing PO for injection.

Despite the predominance of heroin as the drug of choice for initiating injection, a majority of participants (59%) did report ever having injected POs, indicating a significant prevalence of PO injection even in an urban location with a well-established heroin market. The widespread availability of heroin in NYC, however, appears to influence the frequency with which participants reported injecting POs relative to heroin. Although many participants had experimented with injecting POs, it was not often a regular practice: only 26% of respondents reported regular PO injection for at least 1 month (vs. 89% who reported regular heroin injection). On average, these young PWID, who ranged in age from 18 to 29 years old, reported having injected heroin regularly for 2.8 years—about 2 years longer than their reported average duration of regular PO injection (0.8 years). Similarly, when considering the number of days participants reported injecting POs vs. heroin in the past 30 days, heroin was injected far more frequently: 84% reported having injected heroin in the past 30 days, for an average of 18.6 days, while only 14% report having injected POs in the past 30 days, for an average of only 5 days. Nevertheless, the high prevalence of occasional PO injection still poses significant health risks for PWID.

Analyses presented here also indicate that PO injection is significantly correlated with lifetime experience of non-fatal overdose. Similar to other studies [14, 15], our bivariable results indicate a strong correlation between PO injection and overdose. In contrast to these previous studies, however, the association of overdose with PO injection in the current study remained significant in the multivariable model, suggesting a robust association in this sample of young New Yorkers who inject drugs. There are several possible explanations for the observed relationship between PO injection and overdose. On the one hand, PO injectors in this sample are more likely to have grown up in middle- or upper-income families; ergo, they may have more money to spend on opioids and other drugs, which may allow for higher drug intake or polysubstance use, thereby contributing to increased overdose risk. PO injection could also be serving as a marker for a subset of youth who engage in a range of high-risk drug-use behaviors, including behaviors, such as binging on drugs and/or engaging in polysubstance use, that are known to increase risk of overdose.

PO injection was also correlated with having been raised in a higher-income household. This association may possibly reflect the ability of people with higher incomes to continue purchasing POs while concurrently using heroin, which tends to occur in drug contexts where heroin is cheaper and easier to access than POs [20]. Yet, to complicate matters, findings also indicate that lifetime homelessness is significantly correlated with PO injection. This may show that different subsets of the population of young PWID in NYC may be engaging in the injection of multiple drugs [4].

This study has some limitations, particularly pertaining to the use of self-reported and cross-sectional data. Participants’ ability to recall past events and behaviors, including those that may have occurred years prior, is unknown. There is also the possibility that self-reported data is susceptible to social desirability bias, especially given the sensitive and stigmatized topic of illicit drug use. Because of the cross-sectional nature of the data, our findings cannot establish causation, only correlation. Additionally, as this sample was comprised entirely of young adults who live in NYC, results may not generalize to other populations, especially those in non-urban areas. The use of a non-random recruitment strategy—respondent-driven sampling—may also have introduced bias into the sample that limits the generalizability of the findings. An additional limitation in the qualitative data is participants’ imprecise description of the pills used for injection, thus limiting our ability to determine which preparation methods are most common to specific PO formulations (regular extended-release and/or abuse-deterrent).

Study results illustrate the need for harm reduction strategies to address the specific health risks, particularly with regard to HCV transmission, posed by the injection of POs. Knowledgeable people who use drugs, prevention projects and agencies should explicitly inform PWID of the increased viral transmission risk associated with PO injection practices and how to mitigate such risk, mainly by always using new, sterile equipment for every injection, and avoiding the sharing of any injection paraphernalia (syringes, cookers, filters, diluting water, and water containers), even if it contains drug residue. In group injection situations where people are doing multiple injections per injection episode, it can be very difficult to avoid accidental cross-contamination. If there is any sharing or splitting of drug solution from a communal cooker, then all PWID involved need to use a sterile syringe for each injection. In situations where individuals will be re-using their own syringes for repeated injections, all those involved in the group injection should mix their own drugs in their own cooker. If larger syringes are to be used, those with detachable needles should never be used, as they hold a larger amount of residual blood and therefore increase the risk of transmitting HCV or HIV [33]. If sharing POs and injecting, users should try to split the pill before breaking it down for injection, with each individual using exclusively their own injection equipment. Recent research suggests that heating a PO-containing drug solution until boiling reduces the risk of HIV transmission [32]; the extent to which this procedure may protect against HCV transmission is yet unknown but warrants future research.

In summary, these results suggest that a high proportion of young PWID in NYC have injected POs, although it appears to be less frequent than heroin injection. Further, lifetime experience of non-fatal overdose and HCV antibody-positive serostatus were independently associated with having ever injected POs. Existing harm reduction efforts should inform PWID of the increased risks associated with injecting POs and tailor harm reduction messages to address the risky practices associated with preparing and injecting POs, including multiple injections per injection episode and the re-use of drug residue-containing cookers and filters.