Are monks allowed to have prescriptions? What did the Buddha say of medicine? Are Buddhist monks allowed to have prescriptions, or would that be considered an attachment? Did the Buddha say anything of medicine?
Providing the services of a medical practitioner or pharmacist to lay people  is not allowed for monks according to DN2:


  "Whereas some contemplatives &amp; brahmans, living off food given in
  faith, maintain themselves by wrong livelihood, by such "animal" arts
  as: promising gifts to deities in return for favors; fulfilling such
  promises; demonology; reciting spells in earth houses [see earth
  skills, above]; inducing virility and impotence; preparing sites for
  construction; consecrating sites for construction; giving ceremonial
  mouthwashes and ceremonial baths; offering sacrificial fires;
  administering emetics, purges, purges from above, purges from below,
  head-purges; ear-oil, eye-drops, treatments through the nose,
  ointments, and counter-ointments; practicing eye-surgery [or:
  extractive surgery], general surgery, pediatrics; administering
  root-medicines and binding medicinal herbs — he abstains from wrong
  livelihood, from "animal" arts such as these. This, too, is part of
  his virtue."


Monks can use medicine for their own use, according to "The Bhikkhus' Rules: A Guide for Laypeople" by Bhikkhu Ariyesako:


  MEDICINES OR TONICS 
  
  We have dealt above with food and fruit juice. There is now the
  category of 'tonic-medicines' (sattaahakaalika). These can be consumed
  at any time but cannot be stored longer than seven days (after they
  are offered).
  
  These tonic-medicines were originally regulated when Venerable
  Pilindavaccha's great feats of psychic power made him so famous that
  he received many offerings of the five 'tonics.' Even though he
  distributed these among other monks there was so much that the excess
  had to be stored away and their dwellings were overrun by rats.
  Visiting lay people criticized the monks for "storing up goods in
  abundance like a king." The Buddha therefore set down this rule:
  
  "Keeping any of the five tonics — ghee, fresh butter, oil, honey, or
  sugar/molasses — for more than seven days is [an offence of Confession
  with Forfeiture.] (Summarized Nis. Paac. 23; BMC p.242) ◊ There are
  various translations and interpretations about these 'tonic-
  medicines' — according to different Communities and different
  countries. Some places consider only liquids allowable while a few
  communities will drink only plain water in the afternoon. Some
  communities will not accept re-offered tonic-medicines (after the
  seven days period is over), some will under certain circumstances.
  Therefore lay devotees need to enquire about the practice of their
  local Community and follow that way.[94]
  
  Some contemporary observations:
  
  "The five medicines — ghee, navaniita.m, oil, honey, and suga — were
  allowed by the Buddha to be consumed by 'sick' monks at any time of
  the day or night. According to the Mahaavagga, these five were 'agreed
  upon as medicines and, although they served as nutriment for people,
  were not considered as substantial food.' The degree of infirmity
  required before a monk is allowed to consume these [tonic-]medicines
  is a controversial point... It seems that feeling rundown or feeling
  tired after physical exertion would be sufficient cause to be able to
  make use of the Five Medicines."(AB)
  
  "The main effectiveness of these medicines seems to be in their
  nutritional value. They do not have medicinal value as commonly
  understood today, for example, relieving pain or as an antiseptic.
  However, as nutriment they would help to maintain bodily strength and
  assist in recuperation while, since they are so rich, would not be a
  substitute for normal food." (HS ch.10)
  
  Also, if the tonic-medicine is mixed with a tiny amount of food then
  it would be acceptable according to this allowance:
  
  "...if sugar has a little flour mixed with it simply to make it firmer
  — as sometimes happens in sugar cubes and blocks of palm sugar — it is
  still classed as a tonic as it is still regarded simply as 'sugar.'"
  (BMC p.238-9) If the flour is for more food-like reasons then it would
  be counted as food. See also Mixing Edibles above.
  
  LIFETIME MEDICINES  
  
  The fourth category of edibles (see The Four Sorts of Edibles) is that
  of Lifetime Medicines (yaavajiivika). which includes what we generally
  think of as medicines.
  
  The basic principle set down by the Buddha about all medicines is in
  this reflection:
  
  "Properly considering medicinal requisites for curing the sick, I use
  them: simply to ward off any pains of illness that have arisen, and
  for the maximum freedom from disease." [OP p. 47; (Paali: M. I, 10; A.
  III, 387)] In the beginning, the basic (herbal) medicines allowed by
  the Buddha were those pickled in urine. Later, nearly all other types
  came to be considered allowable.[95] (See the separate allowance above
  for 'tonic-medicines.')
  
  Medicines that may be consumed without time limitation are called
  yaavajiivika. The Texts mention different sorts of herbal medicines
  such as: plant roots, e.g., ginger, turmeric, sweet flag, etc.;
  decoctions, such as of the neem or nux-vomica; tree-leaves, such as
  neem-leaves, tulsi or holy basil; fruits, such as long peppers,
  myrobalan, wormwood; resins, such as asafoetida; salts, such as
  sea-salt, rock salt, etc. Any other medicine or herbs similar to these
  that is not reckoned to be food is included under this 'lifetime'
  category.[96]
  
  ◊ Modern western medicines are usually included — using the Great
  Standards — under this category and therefore can be taken at any time
  of the day and kept as long as necessary.


In "Ministering to the Sick and the Terminally Ill", Lily de Silva quotes the Buddha as exhorting monks to care for and look after other monks:


  "He who attends on the sick attends on me," declared the Buddha,
  exhorting his disciples on the importance of ministering to the sick.
  This famous statement was made by the Blessed One when he discovered a
  monk lying in his soiled robes, desperately ill with an acute attack
  of dysentery. With the help of Ananda, the Buddha washed and cleaned
  the sick monk in warm water. On this occasion he reminded the monks
  that they have neither parents nor relatives to look after them, so
  they must look after one another. If the teacher is ill, it is the
  bounden duty of the pupil to look after him, and if the pupil is ill
  it is the teacher's duty to look after the sick pupil. If a teacher or
  a pupil is not available it is the responsibility of the community to
  look after the sick (Vin.i,301ff.).
  
  On another occasion the Buddha discovered a monk whose body was
  covered with sores, his robe sticking to the body with pus oozing from
  the sores. Unable to look after him, his fellow monks had abandoned
  him. On discovering this monk, the Buddha boiled water and washed the
  monk with his own hands, then cleaned and dried his robes. When the
  monk felt comforted the Buddha preached to him and he became an
  arahant, soon after which he passed away (DhpA.i,319). Thus the Buddha
  not only advocated the importance of looking after the sick, he also
  set a noble example by himself ministering to those who were so ill
  that they were even considered repulsive by others.