2 times larger than with a method that examines each product individually. [ 39 ] Adverse effects Like most opioids , unadulterated heroin does not cause many long-term complications other than dependence and constipation . [ 40 ] The average purity of street heroin in the UK varies between 30% and 50% and heroin that has been seized at the border has purity levels between 40% and 60%; this variation has led to people suffering from overdoses as a result of the heroin missing a stage on its journey from port to end user, as each set of hands that the drug passes through adds further adulterants, the strength of the drug reduces, with the effect that if steps are missed, the purity of the drug reaching the end user is higher than they are used to and because they are unable to tolerate the increase, an overdose ensues. [ 41 ] Intravenous use of heroin (and any other substance) with non-sterile needles and syringes or other related equipment may lead to: The risk of contracting blood-borne pathogens such as HIV and hepatitis by the sharing of needles The risk of contracting bacterial or fungal endocarditis and possibly venous sclerosis Physical dependence can result from prolonged use of all opioids, resulting in withdrawal symptoms on cessation of use Decreased kidney function (although it is not currently known if this is because of adulterants or infectious diseases) [ 42 ] Many countries and local governments have begun funding programs that supply