Neuro-Psych Calculators

What neuro-psychiatry covers, and the clinical questions these tools answer

Neuro-psychiatry sits at the interface of brain and mind: epilepsy, movement disorders, traumatic brain injury and dementia on the neurology side; mood, psychotic and anxiety disorders on the psychiatry side; and a large overlap where the two interact. Its distinctive challenge is pharmacologic: drugs that act on the brain carry neurologic risks, and neurologic conditions complicate psychiatric treatment. The three calculators in this library address the medication questions that arise most often at this interface.

The antidepressant tapering calculator builds a gradual dose-reduction schedule for stopping antidepressants. Abrupt discontinuation can trigger discontinuation syndrome, with flu-like symptoms, sleep disturbance, sensory disturbances and rebound anxiety or mood symptoms, and the risk is highest with short-half-life agents. Tapering over weeks to months, slowing further at lower doses, reduces this risk and helps distinguish withdrawal symptoms from relapse of the underlying condition.

The antipsychotic dose equivalence calculator converts doses between antipsychotics using chlorpromazine equivalents, the long-established common currency of antipsychotic potency. When switching agents because of inadequate response or intolerable side effects, equivalence estimates provide the starting point for the new prescription: they translate the current dose into a comparable dose of the replacement drug, which is then individualised. The seizure threshold risk checklist systematically reviews the factors that lower the seizure threshold in patients taking psychotropic medication: a personal or family history of epilepsy, brain injury or lesion, alcohol or benzodiazepine withdrawal, and concurrent use of other proconvulsant drugs.

Several psychotropic drugs are known to lower the seizure threshold, most notably bupropion and clozapine, with the risk rising steeply at higher doses. Many other agents, including several antipsychotics and antidepressants, carry smaller but real risks, and interactions matter: tramadol, for example, adds risk when combined with serotonergic or proconvulsant drugs. The checklist ensures these factors are considered together rather than discovered one by one after a seizure.

When clinicians and students use these calculators

Antidepressant tapering schedules are built in primary care and psychiatry clinics when a patient has recovered and wishes to stop, when side effects demand discontinuation, or when switching between antidepressants. The schedule becomes part of the treatment plan, with follow-up timed to the steps so that emerging symptoms can be distinguished from relapse. Pharmacists use the same principles when counselling patients collecting their final prescriptions.

Dose equivalence calculations arise whenever antipsychotics are switched: for inadequate efficacy, for metabolic or extrapyramidal side effects, or for drug interactions. They are also used when interpreting regimens, comparing the total antipsychotic burden of combination therapy, and in research settings where doses must be standardised across agents. The seizure checklist is most valuable at prescribing moments: before starting bupropion or clozapine, when adding a second proconvulsant drug, or when a patient with epilepsy needs psychotropic treatment.

For students, these tools teach three transferable lessons: that stopping a drug is a pharmacologic intervention in its own right, that potency comparisons between drugs are approximate and context-dependent, and that adverse drug effects emerge from the interaction of drug, dose and patient vulnerability rather than from the drug alone.

Interpreting results: what the tools change in practice

A tapering schedule changes stopping from an event into a process: each step down is small enough that discontinuation symptoms, if they appear, point to the need to slow down rather than to abandon the attempt. Schedules typically span weeks for short courses and months for long-term treatment, with the final steps the slowest, since receptor-level changes are proportionately largest at low doses. If significant withdrawal symptoms emerge, the standard response is to return to the previous tolerated dose, stabilise, and then proceed more slowly.

A chlorpromazine-equivalent conversion gives the prescriber a defensible starting dose for the new antipsychotic, usually then adjusted for the patient's age, comorbidity, previous response and the differing side-effect profiles of the two agents. Equivalence tables are guides to initial dosing, not statements that the drugs are interchangeable milligram for milligram in effect. When the calculated equivalent seems high or low compared with licensed dose ranges, the licensed range and clinical judgement take precedence.

The seizure checklist produces a risk profile rather than a number: each additional risk factor strengthens the case for caution. A patient with no risk factors starting a standard-dose antidepressant needs only routine counselling; a patient with epilepsy, alcohol dependence and a new prescription for bupropion needs a different drug, a neurology opinion, or both. The checklist's value is in making the cumulative risk visible before prescribing rather than obvious after a seizure.

Limitations and pitfalls: what these tools cannot do

Antidepressant tapering must be individualised: published schedules are frameworks, and some patients need slower tapers than any standard schedule provides, particularly after years of treatment or with short-half-life agents. Tapering does not suit every situation; severe relapse risk or urgent side effects may demand faster discontinuation under close supervision. Patients should never adjust the schedule alone based on how they feel on a given day without discussing it with their prescriber.

Chlorpromazine equivalents are approximate by nature: they derive from heterogeneous sources, vary between published tables, and reflect average responses rather than individual ones. They compare dopaminergic potency reasonably well but say nothing about differences in metabolic, cardiac or sedative effects, which often drive switching decisions more than potency does. Equivalence is least reliable at the extremes of dosing and in older or medically complex patients.

The seizure checklist identifies risk factors; it does not quantify absolute seizure risk, which remains low for most psychotropic prescribing. Absence of checklist factors does not guarantee safety, and the list cannot include every interaction or rare vulnerability. These are prescribing aids for qualified clinicians: dose changes to psychotropic medication should always be made with professional supervision, never by self-adjustment based on a calculator.

How to use this library

Use the tapering calculator when a supervised decision to stop an antidepressant has been made, and build the schedule together with the prescriber, with follow-up arranged at the vulnerable steps. Use the dose equivalence calculator at the point of switching antipsychotics, as the starting point for the new prescription rather than its final form. Use the seizure checklist before prescribing proconvulsant psychotropics or adding to an already complex regimen. In all three cases, the calculator structures a decision that a clinician makes; it does not make the decision.

Related specialities

These calculators are often used alongside tools from neighbouring fields:

• Neurology
• Mental Health
• Psychiatry
• Geriatrics

Frequently asked questions