Clearly it needs extensive testing - but the kidney damage potential is at its normal dosage of 5mg/kg of body weight per week, so at even 3% gel suspension it's got to be a way lower dosage than that - especially if they're saying it's effective for up to 6 weeks.
I'm just hoping

. Nearly all of my facial hair is white. I'm not looking forward to all the electrolysis awaiting me when my laser is done

. Expensive and painful. And there don't appear to be options in the UK for getting it done quickly, like you can in the US.