Optimal methadone initiation and dose titration strategies for the treatment of pain have not been determined. Published equianalgesic conversion ratios between methadone and other opioids are imprecise, providing at best, only population averages that cannot be applied consistently to all patients. It should be noted that many commonly cited equianalgesia tables only present relative analgesic potencies of single opioid doses in non-tolerant patients, thus greatly underestimating methadone's analgesic potency, and its potential for adverse effects in repeated-dose settings. Regardless of the dose determination strategy employed, methadone is most safely initiated and titrated using small initial doses and gradual dose adjustments.

As with all opioid drugs, it is necessary to adjust the dosing regimen for each patient individually, taking into account the patient's prior analgesic treatment experience. The following dosing recommendations should only be considered as suggested approaches to what is actually a series of clinical decisions over time in the management of the pain of each individual patient. Prescribers should always follow appropriate pain management principles of careful assessment and ongoing monitoring.

In the selection of an initial dose of methadone, attention should be given to the following:

• The total daily dose, potency and specific characteristics of the opioid the patient had been taking previously, if any;
• The relative potency estimate used to calculate an equianalgesic starting methadone dose, in particular, whether it is intended for use in acute or chronic methadone dosing;
• The patient's degree of opioid tolerance;
• The age, general condition and medical status of the patient;
• Concurrent medications, particularly other CNS and respiratory depressants;
• The type, severity and expected duration of the patient's pain;
• The acceptable balance between pain control and adverse side effects.

Body as a whole

• muscle spasticity

Respiratory

• difficulty breathing
• slow, shallow and labored breathing
• stopped breathing (sometimes fatal within 2-4 hours)

Eyes, ears, nose and throat

• pinpoint pupils
• bluish skin
• bluish fingernails and lips

Gastrointestinal

• spasms of the stomach and/or intestinal tract
• constipation

Heart and blood vessels

• weak pulse
• low blood pressure

Nervous system

• drowsiness
• disorientation
• coma

As an opiate, regular use of methadone causes physical dependency - if you've been using it regularly (prescribed or not) once you stop you will experience a withdrawal. The physical changes due to the drug are similar to other opiates (like heroin); suppressed cough reflex, contracted pupils, drowsiness and constipation. Some methadone users feel sick when they first use the drug. If you are a woman using methadone you may not have regular periods - but you are still able to conceive. Methadone is a long-acting opioid; it has an effect for up to 36 hours (if you are using methadone you will not withdraw for this period) and can remain in your body for several days.