Ciclosporin Unit Converter
Ciclosporin Unit Converter
Convert whole-blood ciclosporin between ng/mL and nmol/L, with the C0 versus C2 sampling question and the toxicities that distinguish it from tacrolimus.
Ciclosporin converter
Mass ⇄ molarCiclosporin C0 trough 150 ng/mL
Formula and conversion factor
ng/mL = nmol/L ÷ 0.8315
- 0.8315
- derived from the molecular weight of ciclosporin A, 1202.61 Da (1000 ÷ 1202.61)
- µg/L
- numerically identical to ng/mL
- C0 / C2
- trough and 2-hour post-dose levels are not interchangeable — the sampling point must be stated alongside the result
Worked example
Ciclosporin C0 trough 150 ng/mL
150 × 0.8315 = 124.7 nmol/L
= 150 µg/L
C0 trough targets, maintenance therapy
| Phase | Target C0 (ng/mL) |
|---|---|
| Early post-transplant | 200 – 350 |
| Maintenance | 100 – 200 |
Distinguishing ciclosporin from tacrolimus toxicity
| Shared toxicity | Ciclosporin-specific |
|---|---|
| Nephrotoxicity | Gum (gingival) hypertrophy |
| Hypertension | Hirsutism |
Whole blood, and which trough
Like tacrolimus, ciclosporin is measured in whole blood rather than serum or plasma, because the drug distributes substantially into red blood cells and a plasma sample under-represents true exposure.
Most centres monitor a trough level (C0), drawn immediately before the next dose. Some monitor C2 instead — a level drawn exactly two hours after dosing — because for the microemulsion formulation the 2-hour concentration correlates better with total drug exposure, the area under the concentration-time curve, than the trough does. C0 and C2 are not interchangeable, and a result should always be labelled with which sampling point produced it.
Formulation matters as much as sampling point. The original oil-based preparation and the microemulsion formulation are not bioequivalent — switching between them changes absorption unpredictably, and a patient converted from one to the other needs re-monitoring rather than an assumption that the same dose will give the same level.
Ciclosporin shares tacrolimus’s dependence on CYP3A4 for clearance, so the same interacting drugs apply in both directions: azole antifungals, macrolides, diltiazem and grapefruit raise levels; rifampicin, phenytoin, carbamazepine and St John’s wort lower them.
Clinically, ciclosporin’s toxicity profile differs from tacrolimus’s in ways that are useful at the bedside. Both cause nephrotoxicity and hypertension, but ciclosporin characteristically also causes gum (gingival) hypertrophy and hirsutism — findings that are unusual with tacrolimus and can help distinguish the two agents’ effects when a patient has been switched between them or the history is unclear.
Frequently asked questions
How do I convert ciclosporin from ng/mL to nmol/L?
Multiply by 0.8315. A C0 trough of 150 ng/mL is 124.7 nmol/L. The factor comes from ciclosporin’s molecular weight of 1202.61 Da.
What is the difference between C0 and C2 monitoring?
C0 is the trough level drawn before the next dose; C2 is drawn exactly two hours after dosing and correlates better with total exposure for the microemulsion formulation. They are not interchangeable, and results should always be labelled.
Can I switch between ciclosporin formulations without re-checking levels?
No. The original and microemulsion preparations are not bioequivalent — switching changes absorption and requires a fresh level after the change.
How do I tell ciclosporin toxicity from tacrolimus toxicity?
Both cause nephrotoxicity and hypertension, but gum hypertrophy and hirsutism are characteristic of ciclosporin and unusual with tacrolimus.
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References
- Levy G et al. Consensus on Neoral C2 monitoring in liver transplantation. Transplantation. 2002;73(9 Suppl):S12–8.
- Morris RG. Cyclosporin therapeutic drug monitoring — an update. Ann Clin Biochem. 2003;40(4):353–68.