Here's a list of the drugs clients are using at London's overdose prevention site

What drugs are clients at London's Temporary Overdose Prevention (TOPS) site using?

That's the question we put to staff of the facility, which has handled almost5,000 client visits since opening in February.

The list shows that opioids likehydromorphoneand fentanyl continue to be in steady use among Londoners who inject drugs.

Sonja Burke is the director of Counterpoint Harm Reduction Services, which operates the site.

She said the drugs on the list didn't surprise her, although she was somewhat surprised that crystal meth didn't appear in the top spot.

The list below is based on anecdotal self-reporting from clients, so Burke cautions that it should not be considered a comprehensive survey. Also, because not all London's drug users visit TOPS, this list can only offer a limited view into which drugs are being consumed locally.

Here's the list:

1. Hydromorphone

This strong opioidis available in capsule form but users typically crush the capsules down and mix the beads with water for injection. This creates a more intense, immediate high. Unlike its brand-name equivalent Dilaudid(number three on this list) hydromorphone can be injected more than once after the initial mixing. This allows users to get more out of one capsule, but it also increases the chance of infection if residue remains in the bowl (called a cooker) used to mix and heat it. "If a person is using the same cooker multiple times, then it gives the opportunity for the bacteria to grow," said Burke. This can lead to infections like endocarditis and flesh-eating disease.

Along with clean syringes, London's TOPS provides clients with sanitary, single-use disposablecookers to cut down on infections.

A drug user named John who spoke to CBC News said the appeal ofhydromorphoneis its low price and relatively easy availability.

"It's the time release that makes it really popular," he said. "For $20, it goes a long way."

2. Crystal meth

Also commonly injected, this drug remains popular because at $5 a dose, it's a cheap high. Meth is a popular alternative for users having trouble obtaining opioids likehydromorphoneand fentanyl. Burke says meth use spiked when OxyContin a highly addictiveopioidpill commonly crushed down for intravenous use was replaced byOxyNeoin 2012. OxyNeocan't be crushed down, limiting its appealfor users who want the more intense high that comes from injecting the drug. "When there's nothing else, people turn to crystal meth," said Burke. She said people struggling with homelessness often use meth "to stay alert and awake throughout the night to protect their safety."

3. Dilaudid

This is the brand name of hydromorphonebut it comes in pill form, not capsules. Pills crushed into a powder for IV use can only be used once, which limits their appeal. Still, it's easy enough to get with a prescription, which explains much of its popularlity.

4. Morphine and methadone

These remain more popular among TOPS clients thanheroin.

5. Fentanyl

A growing driver of Canada's opioidcrisis, fentanylis deadly not only for its potencybut because it's often mixed into other drugs by dealers. Users who take it unknowingly are at risk. "It's also really challenging with powdered fentanylto know the dosage," said Burke. "People may think it's evenly mixed with another substance and it's not. So one dose may have a small amount and the next dose may have a large amount." Burke also said clients tell her the availability of fentanylin London isn't constant, but can rise and fall.

Permanent site still a priority

London's TOPS operates out of a cramped space at186 King St. There have been many successes. Clients are accessing resources, such as addiction counselling. But Burke says moving to a permanent site would improve client care. The Middlesex-London Health Unit has narrowed the search down to two sites.

"Right now we are busy, so we have lots of people in the waiting room," said Burke. But a permanent site "would definitely help us serve more people."