Brief Answer:
narcotics cannot be prescribed

Detailed Answer:
without being in the same state as the person.
They cannot be prescribed except by a written prescription.
And, reasonably, they shouldn't be prescribed unless the person has a documented need, by their own physician with whom they have a long-standing relationship. Reasonably I cannot say I know very much about you. Therefore, do take this as general information and certainly not about you in particular:
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Narcotic addiction is a complex cognitive disorder. The drug activates pleasure switched in the brain and causes a pretty straightforward reward cycle.. take the pill.. feel good. Secondary effects on other triggers to think about taking the drug (context, thoughts, feelings, emotions) and progressively having more of one's surroundings be associated with drug taking lead to addiction. IN addiction, there is cognitive distortion leading everything to get involved with taking the drug. These in turn, lead people to progressively more distorted behaviors to get narcotics (wheedling the doctor, multiple doctors, extra legal sources such as street sellers and internet sellers). These can lead to very serious legal and health consequences.

To get out of this, first, acknowledging it at least a little bit. Then there's several paths depending on how much one wants to acknowledge.
NOt at all: pain management.
Somewhat: suboxone treatment
Quite a lot: rehab, addiction, or methadone programs
and.... literally the more you acknowledge the situation the better it goes for someone:
Quite openly and publicly... somewhere between a 50/50 (most estimates on participating in a 12 step program) to an over 90% long term success rate (very unusual very public programs)
Slightly open (counseling)... about 25% success
Guilt and hiding things.. not very successful.

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Brief Answer:
as mentioned, would legally require a script

Detailed Answer:
300 ml isn't a usual dose
Oramorph 10mg/5ml oral solution so..... 300 mg per week.... high average or 600 mg/ week rather into a scary range. But the dose is reported in milligram (measure of stuff) rather than milliliter (measure of volume).

And....
without being in the same state as the person.
They cannot be prescribed except by a written prescription.
And, reasonably, they shouldn't be prescribed unless the person has a documented need, by their own physician with whom they have a long-standing relationship. Reasonably I cannot say I know very much about you. Therefore, do take this as general information and certainly not about you in particular:
Very high amounts of narcotics without a script is HIGHLY ILLEGAL. so... this would preclude legitimate sources and I wouldn't know others.

Cannot say in your particular case and...
signs of narcotic addiction include and are not limited to:
being on a high amount of narcotics
not having bounds on use of narcotics
asking for more than prescribed amounts
going around one's doctor to get it
looking for extralegal ways of getting narcotics

Narcotics have a few key points that set up rather bad situations in addiction:
They do not actually remove the source of pain. If someone has a tooth infection or a punch in the jaw, the underlying disorder is either gone or goes away with treatment. The inflammation is removed with anti-inflammatories so the source of pain is gone. Narcotics don't do this.
Indeed, one gets used to a particular dose and more is required for the same effect (tolerance).
There can be possibly other intrinsic effects on judgment and thinking due to them. This is a controversial subject whether it is intrinsically the drug or the context or genetic predisposition or volitional that causes the changes in judgment and perception associated with narcotic addition.

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