Muscle relaxants

Baclofen, from about $34, prescribed for spasticity arising from multiple sclerosis, spinal cord injury and related neurological conditions. It acts on GABA-B receptors in the spinal cord rather than on the muscle itself, which is why it also reduces the painful flexor spasms that are often the worst part of spasticity.

Two things about it are routinely underestimated. The first is that spasticity is sometimes doing useful work — in someone whose weak legs depend on extensor tone to stand or transfer, removing that tone removes the ability to weight-bear. The dose is therefore titrated to the point where spasm is tolerable rather than abolished, and that endpoint is individual.

The second is withdrawal. Stopping baclofen abruptly after regular use can produce rebound spasticity far worse than the original, with fever, confusion and in severe cases seizures. It is tapered over one to two weeks, always. Drowsiness and weakness dominate the first days of treatment and usually settle as the dose is built up slowly; starting at the full target dose is the common reason someone concludes they cannot tolerate it.

Titration, and why it takes weeks

Baclofen is started low and built up every three days or so, because drowsiness and weakness dominate the first days of each increase and settle before the next. Reaching an effective dose takes weeks rather than days, and starting at the target dose is the usual reason someone concludes they cannot tolerate it at all.

Why some spasticity is worth keeping

In someone whose legs are weak, extensor tone may be what allows standing, transferring and walking. Abolishing it removes the function with it. The target is therefore tolerable spasm with the painful spasms suppressed, not zero tone — and that endpoint is individual, which is why a physiotherapist is part of setting it.

The withdrawal risk, and how to design against it

Stopping abruptly after regular use produces rebound spasticity worse than the original, with fever, confusion and in severe cases seizures. The taper is one to two weeks, always, and that applies to accidental stopping as much as planned. Running out is the situation to design against: keep a margin, order ahead, and treat a supply problem as something to act on the same day.

When spasticity suddenly worsens

Look for a cause before changing the dose. Urinary infection, constipation, a pressure sore, an ingrowing toenail and tight clothing all increase spasticity and are treatable in their own right. Increasing the dose in response to a treatable trigger adds sedation without addressing anything.

Driving, work and the first fortnight

Sedation is heaviest while the dose is being built up and again after any increase. That is the period to arrange around: no driving until the response at a given dose is known, no operating machinery, and real caution with alcohol, which compounds the effect rather than adding to it. Once a dose has been stable for a week or two, most people function normally on it.

What adds to the sedation

Baclofen’s drowsiness is additive with everything else that depresses the central nervous system, and the combinations people run into are rarely exotic: alcohol, sleeping tablets, strong painkillers, sedating antihistamines bought for hay fever, and some antidepressants. The effect is not the sum of two mild ones; it is disproportionate, and falls are the commonest consequence in anyone whose balance is already affected. Older patients and those with reduced kidney function reach that point at much lower doses, which is why their titration is slower and their maximum lower.

Kidneys, and why the dose is not the same for everyone

Baclofen is cleared almost entirely by the kidneys, so reduced renal function raises blood levels at an unchanged dose. The result — confusion, excessive drowsiness, sometimes hallucinations — is regularly mistaken for a new neurological problem rather than recognised as accumulation. Anyone with known kidney impairment starts lower and increases more slowly, and any acute illness that affects the kidneys is a reason to review the dose rather than continue regardless.